discussion of electric stun guns and devices until development of laser beam weapons and electronics circuits AMNIMARJESLOW GOVERNMENT 91220017 XI XA PIN PING HUNG CHOP 02096010014 LJBUSAF GO FAR AND LOOP WIND TO STAR BORG LASER GUN JUMP IN LOGIC STRUCTURE ELECTRONICS HARD AND SOFT XXX PRO SPACE LIFE 2020 DONE

                                          

                        Electroshock weapon 

An electroshock weapon is an incapacitating weapon. It delivers an electric shock aimed at temporarily disrupting muscle functions and/or inflicting pain without causing significant injury.

Many types of these devices exist. Stun guns, batons (or prods), and belts administer an electric shock by direct contact, whereas Tasers (conducted electrical weapons) fire projectiles that administer the shock through thin flexible wires. Long-range electroshock projectiles, which can be fired from ordinary shotguns and do not need the wires, have also been developed. 

                                               

                      A Taser, with cartridge removed, making an electric arc between its two electrodes 

Jack Cover, a NASA researcher, began developing the Taser in 1969. By 1974, he had completed the device, which he named after his childhood hero Tom Swift ("Thomas A. Swift's electric rifle"). The Taser Public Defender used gunpowder as its propellant, which led the Bureau of Alcohol, Tobacco and Firearms to classify it as a firearm in 1976. Cover's patent was adapted by Nova Technologies in 1983 for the Nova XR-5000, their first non-projectile hand-held style stun gun. The XR-5000 design was widely copied as the source for the compact handheld stun gun used today.

Principle of operation

Electroshock weapon technology uses a temporary high-voltage, low-current electrical discharge to override the body's muscle-triggering mechanisms. Commonly referred to as a stun gun, electroshock weapons are a relative of cattle prods, which have been around for over 100 years and are the precursor of stun guns. The recipient is immobilized via two metal probes connected via wires to the electroshock device. The recipient feels pain, and can be momentarily paralyzed while an electric current is being applied. Essential to the operation of electroshock, stun guns and cattle prods is sufficient current to allow the weapon to stun. Without current these weapons cannot stun and the degree to which the weapon is capable of stunning depends on its proper use of current. It is reported that applying electroshock devices to more sensitive parts of the body is even more painful. The maximum effective areas for stun gun usage are upper shoulder, below the rib cage, and the upper hip. High voltages are used, but because most devices use a non-lethal current, death does not usually occur from a single shock.The resulting "shock" is caused by muscles twitching uncontrollably, appearing as muscle spasms.

The internal circuits of most electroshock weapons are fairly simple, based on either an oscillator, resonant circuit (a power inverter), and step-up transformer or a diode-capacitor voltage multiplier to achieve an alternating high-voltage discharge or a continuous direct-current discharge. It may be powered by one or more batteries depending on manufacturer and model. The amount of current generated depends on what stunning capabilities are desired, but without proper current calculations, the cause and effect of high voltage is muted. Output voltage is claimed to be in the range of 100 V up to 6 kV; current intensity output is claimed to be in the range of 100 to 500 mA; individual impulse duration is claimed to be in the range of 10 to 100 µs (microseconds); frequency of impulse is claimed to be in the range of 2 to 40 Hz; electrical charge delivered is claimed to be in the range of 15 to 500 µC (microcoulombs); energy delivered is claimed to be in the range of 0.9 to 10 J. The output current upon contact with the target will depend on various factors such as target's resistance, skin type, moisture, bodily salinity, clothing, the electroshock weapon's internal circuitry, discharge waveform, and battery conditions.

Manufacturers' instructions and manuals shipped with the products state that a half-second shock duration will cause intense pain and muscle contractions, startling most people greatly. Two to three seconds will often cause the recipient to become dazed and drop to the ground, and over three seconds will usually completely disorient and drop the recipient for at least several seconds. TASER International warns law enforcement agencies that "prolonged or continuous exposure(s) to the TASER device’s electrical charge" may lead to medical risks such as cumulative exhaustion and breathing impairment.

Because there was no automatic stop on older model Taser guns, many officers have used it repeatedly or for a prolonged period of time, thus potentially contributing to suspects’ injuries or death.The current X26 model automatically stops five seconds after the trigger is depressed and then the trigger must be depressed again to send another shock. The trigger can be held down continuously for a longer shock or the device can be switched off before the full five seconds have elapsed. The devices have no protections against multiple police officers giving multiple shocks, cumulatively exceeding the recommended maximum levels.

Countermeasures

There is a fabric that purports to protect the wearer from Tasers or other electroshock weapons.

Commercially available varieties

Compact stun guns

A concealable weapon shaped and sized like a lipstick tube

Mobile phone-style stun gun

Compact stun guns

The compact handheld stun guns are about the size of a TV remote or calculator, and they must touch the subject when used. The original XR-5000 design in 1983 had the electrodes spread farther apart to make the noisy electric arc between the electrodes as a more visible warning. Some such devices are available disguised as other objects, such as umbrellas, mobile phones or pens.

Electric shock prods

Electric cattle prod from the 1950s

The larger baton-style prods are similar in basic design to an electric cattle prod. It has a metal end split into two parts electrically insulated from each other, or two thin projecting metal electrodes about 2.5 centimetres (1 in) apart, at an end of a shaft containing the batteries and mechanism. At the other end of the shaft are a handle and a switch. Both electrodes must touch the subject. In some types the sides of the baton can be electrified to stop the subject from grasping the baton above the electrodes.

Some models are built into long flashlights also designed to administer an electric shock with its lit end's metal surround (which is split into halves insulated from each other).

Stun belts

A stun belt is a belt that is fastened around the subject's waist, leg, or arm that carries a battery and control pack, and contains features to stop the subject from unfastening or removing it. A remote-control signal is sent to tell the control pack to give the subject an electric shock. Some models are activated by the subject's movement.

The United States uses these devices to control prisoners. One type is the REACT belt. Some stun belts can restrain the subject's hands and have a strap going under his groin to stop him from rotating the belt around his waist to reach its battery and control pack and trying to deactivate it. Stun belts are not generally available to the public.

Stun shields

Stun shields are shields with electrodes embedded into the face, originally marketed for animal control, that have been adopted for riot control.

Tasers

Raysun X-1, a multi-purpose handheld weapon that fires two stun probes (for high-voltage shocks), rubber bullets, pepper, and paintballs. Without the probes it works as a stun gun.

Taser Stoper C2, with cartridge removed. A self-defense weapon.

Shooting stun gun

The shooting stun guns fire two small dart-like electrodes, which stay connected to the main unit by conductors, to deliver electric current to disrupt voluntary control of muscles causing "neuromuscular incapacitation".

Wireless long-range electric shock weapon

Taser International has developed a long-range wireless electro-shock projectile called XREP (eXtended Range Electro-Muscular Projectile), which can be fired from any 12-gauge shotgun. It contains a small high-voltage battery. Its range is currently 30 metres (98 ft), but the U.S. Department of Defense, which funded development for the technology, expected delivery of a 90 metres (300 ft) range projectile of this type from the company in 2007. An XREP projectile was controversially used by British police during the 2010 Northumbria Police manhunt  It subsequently transpired that the XREP has never been officially approved for use in the United Kingdom and the weapon system was provided unrequested to the police at the scene directly by the civilian company which distributes Taser International's products in the UK. The company's licence to provide Taser systems was afterwards revoked by the Home Secretary Theresa May.

Stun gun

The stun gun comes in several voltage options ranging from 2.5 million to 4.5 million volts, giving the user how strong the shock will be. Depending on the voltage and the length of time the device is pressed against the attacker, the effects can last several for several minutes up to half an hour.

Prototype designs

Due to increased interest in developing non-lethal weapons, mainly from the U.S. Military, a number of new types of electroshock weapon are being researched. They are designed to provide a "ranged" non-lethal weapon.

The electrolaser is a prototype weapon that uses a laser to create a conducting ionized channel through the air.

A shockround is a piezo-electric projectile that generates and releases electric charge on impact.

Weapons that administer electric shock through a stream of fluid

Prototype electroshock guns exist that replace the solid wire with a stream of conductive liquid (e.g., salt water), which offers the range of a Taser (or better) and the possibility of multiple shots. . According to the proponents of this technology, difficulties associated with this experimental design include:

• "Non-continuous" discharge onto subject: liquid stream needs over 9 metres (30 ft) and over 5-second discharge
• "Pooling" of conductive liquid at base of subject, making apprehension of subject difficult by observing officers
• Need to carry a large tank of the liquid used, and a propellant canister, like a "water gun", to administer consecutive bursts of liquid over distances.

Another design, announced by Rheinmetall W&M as a prototype in 2003, uses an aerosol as the conductive medium. The manufacturers called it a "Plasma Taser"; however, this is only a marketing name, and the weapon does not use plasma. According to the proponents of this technology, problems associated with this design include:

• Poor electrical conductivity
• Range of concept design is minimal (a gas cannot be propelled greater than 3 metres (9.8 ft) effectively)
• The "gassing effect": all subjects in enclosed spaces are subjected to the same effects

Controversies

Because of the use of electricity and the claim of the weapon being non-lethal, controversy has sprouted over particular incidents involving the weapon and the use of the weapon in general. In essence, controversy has been centered on the justification of the use of the weapon in certain instances, and, in some cases, health issues that are claimed to be due to the use of the weapon.

Tests conducted by the Cleveland Clinic found that Tasers did not interfere with pacemakers and implantable defibrillators. A study conducted by emergency medicine physicians at the University of California, San Diego (UCSD) Medical Center showed no lasting effects of the Taser on healthy test subjects. However, Taser International no longer claims the devices are "non-lethal", instead saying they "are more effective and safer than other use-of-force options".

Currently, Tasers are programmed to be activated in automatic five second bursts, although the officer can stop the energy charge at any time by engaging the safety switch. The charge can also be prolonged beyond five seconds if the trigger is held down continuously. The operator can also inflict repeated shock cycles with each pull of the trigger as long as both barbs remain attached to the subject. The only technical limit to the number or length of the electrical cycles is the life of the battery, which can be ten minutes or more.

Concerns about the use of conducted electrical weapons have arisen from cases that include the death of the Polish immigrant Robert Dziekanski in the Vancouver, BC airport where he died after the RCMP officer, in spite of his training, repeatedly stunned him with a Taser. The report by forensic pathologist Charles Lee, of Vancouver General Hospital, listed the principal cause of death as "sudden death during restraint", with a contributory factor of "chronic alcoholism".

A similar incident occurred in Sydney, Australia, to Roberto Laudisio Curti, a 21-year-old tourist from Brazil. He died after repeated Taser application even after being physically apprehended (by the weight of several police officers lying on top of him compressing his chest and making it hard to breathe. He was pepper sprayed at the same time). The Coroner was scathing of the "thuggish" behaviour of the police. The repeated use of several Tasers was considered excessive and unnecessary.

The study  done by Pierre Savard, Ing., PhD., Ecole Polythechnique de Montréal, et al., for the Canadian Broadcasting Corporation (CBC), indicated that the threshold of energy needed to induce deadly ventricular fibrillation decreased dramatically with each successive burst of pulses; however, one pulse may provide enough energy to induce deadly ventricular fibrillation in some cases. The threshold for women may be less.

Although the Taser is a programmable device, the controlling software does not limit the number of the bursts of pulses and the time between bursts while the trigger is held down continuously, or the number of times the shock cycles can be repeated. Thus the design does not adequately reduce the likelihood that the victim's heart enters into a deadly ventricular fibrillation.

Legal issues

Electroshock weapons have been made illegal in Germany by supplement 2 WaffG if they do not carry an official seal of approval demonstrating they do not constitute a health risk. As of July, 2011, no such seal has been issued to any device on the market. According to § 40 Abs. 4 WaffG, the German federal police may approve of exceptions though. Such a special approval for purchase, ownership and carrying was in effect until 31 December 2010. As of 1 January 2011, only devices carrying the PTB's seal of approval are legal. Previous owners may keep their devices, but cannot carry or sell them. Electroshock weapons effective over a distance, like airtasers, have been completely outlawed in Germany since 1 April 2008.

In the United Kingdom the possession and purchase of any weapon of whatever description designed or adapted for the discharge of any noxious liquid, gas or other thing is prohibited. This includes electroshock weapons . 

Torture 

The United Nations Committee against Torture reports that the use of Tasers can be a form of torture, due to the acute pain they cause, and warns against the possibility of death in some cases.  The use of stun belts has been condemned by Amnesty International as torture, not only for the physical pain the devices cause, but also for their heightened abuse potential, due to their perceived "harmlessness" in terms of causing initial injuries, like ordinary police batons do. Amnesty International has reported several alleged cases of excessive electroshock gun use that possibly amount to torture. They have also raised extensive concerns about the use of other electro-shock devices by American police and in American prisons, as they can be (and according to Amnesty International, sometimes are) used to inflict cruel pain on individuals.

Tasers may also not leave the telltale markings that a conventional beating might. The American Civil Liberties Union has also raised concerns about their use, as has the British human rights organization Resist Cardiac Arrest

                    Cardiac stimulation with high voltage discharge from stun guns

The ability of an electrical discharge to stimulate the heart depends on the duration of the pulse, the voltage and the current density that reaches the heart. Stun guns deliver very short electrical pulses with minimal amount of current at high voltages. We discuss external stimulation of the heart by high voltage discharges and review studies that have evaluated the potential of stun guns to stimulate cardiac muscle. Despite theoretical analyses and animal studies which suggest that stun guns cannot and do not affect the heart, 3 independent investigators have shown cardiac stimulation by stun guns. Additional research studies involving people are needed to resolve the conflicting theoretical and experimental findings and to aid in the design of stun guns that are unable to stimulate the heart.

Stun guns are used to physically incapacitate a person by discharging controlled electrical energy into the body, thereby preventing effective muscular activity. Although the intention is to provide a safe means of subduing an uncooperative person, some studies have suggested that stun guns can stimulate cardiac muscle in addition to skeletal muscle, thus potentially promoting lethal cardiac arrhythmias. In this article, we review the scientific data about the direct effects of stun gun discharges on the heart during shock delivery. We discuss these issues in terms of electrostimulation and correlate them with theoretical and experimental data in the literature. We discuss the principles of cardiac stimulation from internal and external stimulation and examine the evidence for and against cardiac stimulation by stun gun discharges. 

Stun gun discharges

An older method of stun guns application, called “drive-stun,” functioned like a cattle prod, which required direct contact between the electrodes of the source and the target. Stun guns are manufactured by different manufacturers (e.g., Aegis Industries, Stinger Systems, Taser International) and they operate under the general principle of high-voltage discharge with short pulse durations. However, their operation and shock charecteristics vary by manufacturer. For example, a recent model (X26, TASER International) feature 2 barbs attached to long copper wires that are rapidly propelled by compressed nitrogen and adhere to the target's skin or clothes. This stun gun generates an initial 3 microsecond electric pulse, which produces an electrical arc that creates a low-impedance pathway for electricity to reach the body with or without skin contact.1 The initial pulse is followed by longer pulses (100 microseconds) that deliver electrical energy to the target's body, which stimulates his or her nerves and skeletal muscles and results in incapacitation. This pattern is repeated at a frequency of 19 pulses per second. Incapacitation lasts for the duration of the discharge, which is typically 5 seconds but can be 15 seconds or longer if pressure on the trigger is maintained. The TASER X26 battery has the capacity to deliver up to 195 discharges of 5 seconds each,1which corresponds to a duration of over 15 minutes. Other devices that have been studied include the M26 (TASER International) and the MK63 Trident (Aegis Industries), which is a stun baton. Each of these devices uses high frequency electrical pulses to incapacitate the target.

Method of stunning

Stunning can be attributed to 1 of 2 methods, which depend on the mode of application. In the “drive stun” method, the overwhelming factor is the creation of pain and hence compliance. The second method, in which electrodes are fired toward the target as projectiles, neuromuscular stimulation occurs over a larger area. In addition to pain, the device incapacitates the target by stimulating his or her motor nerves and muscles as well as sensory neurons. The duration and frequency of the pulses have been optimized to incapacitate the target, and different devices have varying effects depending on the frequency of stimulation and the shape of the electrical pulse.

Electrical stimulation of the heart

Since the early 1900s,2,3 various equations have been proposed to describe the relation between the current and pulse duration required for electrostimulation of the heart. These formulas showed an inverse relation between the duration and the current of the stimulating pulse, which means that if the pulse duration is short, a higher current is required for stimulation.4

For an electrical pulse to stimulate the heart, it must depolarize the cardiac membrane below a certain level and the induced depolarization must be propagated throughout the heart. The duration and strength of the pulse must be sufficient to allow cell membranes to react and reach an excitation threshold above which activation is triggered. This activation produces a wave front resulting in mechanical contraction of the heart muscle. Shorter pulse durations require larger amounts of current or charge to stimulate the heart. Thus, one must consider whether a stun gun discharge, which is external to the heart, can deliver enough current to stimulate the heart. Below we discuss the external stimulation of the heart under other known circumstances and relate it to a typical electrical pulse generated by a stun gun.:

Effect of external electrical discharges on the heart

The ability of external electrical discharges to alter the internal electrical activity of the heart (e.g., to induce ventricular fibrillation) has long been recognized.5 Depending on the method of delivery and the amount, timing and location of the electrical discharge, an external discharge can produce a beat when one is absent, induce fatal cardiac arrhythmias or restore a normal heart beat to a heart in arrhythmia.6 The use of external electrical discharges to influence the heart has resulted in the development of external pacemakers (e.g., Zoll stimulator) and defibrillator devices to treat ventricular fibrillation. However, these discharges are delivered under controlled conditions at rates that are physiologic or that are delivered during the safe part of the cardiac cycle. High voltage discharges commonly occur in various forms, from electrostatic discharge (most common) to electrocution or lightning strike (least common). Internal cardiac defibrillators also use high voltage pulses for terminating ventricular fibrillation. The relative values for voltage, current and energy for some common sources of high-voltage shocks, along with the most common type of stun gun in use, are shown in Table 1.

Table 1

The physiologic effects of shocks from these sources vary depending on the duration, frequency and energy of the discharges. Burn injuries are usually local and minor for most sources, except for line voltage if the body is in contact long enough for heat to accumulate (Joule effect). In contrast, the major consequence of a lightning strike is a phenomenon known as electroporation, which creates holes or pores in cell membranes. This disruption can wreak havoc on nerve and muscle tissues. In addition, secondary currents induced by the magnetic field generated by the large current of a lightning strike could be large enough to cause cardiac arrest and seizure.

In contrast, discharges from static electricity (electrostatic discharge) or from a stun gun involve a small amount of energy (less than 1 joule). In both cases, electricity travels to the skin through an arc that provides a low impedance path, allowing the current to flow between the source and the target. The amount of energy is too small to create burns or local electroporation. In the case of electrostatic discharge, a brief uncomfortable shock is felt, but it has no physiologic consequences. The pain is perceived through sensory nerves. The operation of most stun guns is thought to rely on their effect on motor function, and pain is a collateral, but intense, effect. The frequency and the shape of the pulses generated by stun guns are designed to incapacitate the target by electrically overwhelming his or her control of these muscles. Though the experimental evidence supporting these claims is not entirely clear, the net effect is that the target cannot control his or her skeletal muscles. This effect lasts for at least the duration of the discharge. In principle, these pulses are designed to act only on skeletal muscles and to not affect internal organs such as the heart.

Evidence that stun guns cannot stimulate the heart

Despite the fact that stun guns are widely used and that their practical safety is under scrutiny, the majority of these analyses are theoretical in nature. These theoretical analyses suggest that stun guns cannot deliver the amount of energy required to stimulate the heart or cause ventricular fibrillation. Most theoretical studies base their arguments on the following principles: only a small portion (4%–10%) of the current that reaches the chest will affect the heart and the time constant of the cardiac cell membrane is much longer than the pulse duration generated by stun guns. According to the law of electrostimulation and given the electrical characteristics of stun gun pulses and cardiac cells, cardiac electrostimulation should not occur during a stun gun shock.8 These analyses support the claim that electrical pulses generated by stun guns are designed to specifically target skeletal muscle, which has a much smaller time constant (i.e., refractoriness) compared with cardiac cells.

Experimental studies that support the claim that stun guns do not stimulate the heart base their arguments on conservative device settings and experimental designs that often do not reflect a clinically relevant or “worst case” scenario. The studies by Lakkireddy and colleagues14 and McDaniel and colleagues, both involving swine, used a modified stun gun for which the output power could be controlled, allowing the authors to specify a safety margin for the device and to demonstrate that it could not induce ventricular fibrillation. McDaniel and colleagues used arterial blood pressure tracing, which showed no perturbations during discharge from the stun gun simulator. However, intracardiac electrograms from the study by Lakkireddy and colleagues showed that the pulses did influence heart rate during shock delivery if the barbs were located such that they formed a vector crossing the heart. In contrast, the MK63 stun baton in the “drive stun” mode applied to the anterior thigh or thorax of Yucatan miniature pigs did not induce acute arrhythmias. The authors of both studies attributed their findings of a lack of cardiac stimulation to possible differences in electrode spacing, proprietary waveform or power generated by the device.

Other studies have been performed using healthy volunteers (police officers). Each volunteer received a single 5 second stun gun pulse to his or her back. This does not reflect the common scenario, in which multiple, prolonged shocks are delivered with the possibility of the barbs landing near the thorax. These studies recorded electrocardiogram findings before and after, but not during, the stun gun discharge. This, however, does not rule out the possibility of disturbances in the rhythm during the discharge owing to the artifacts in recorded electrocardiograms during the discharge. These limitations prevented the researchers from observing transient changes in heart rhythm during discharges. The immediate recordings after the discharges showed shortening and lengthening of QT complexes without assigning any significance to these changes.

Stun gun discharges have been recorded in the field and there have been no claims of deaths medically attributed to these discharges. These recordings were made immediately after, but not during, the discharge. Although this does not affect the claim of no related deaths, these studies cannot verify whether the heart was stimulated during discharge. In cases of recorded deaths, the mode of death had never been established, though a state of “excited delirium” has been reported .  However, excited delirium has not been listed as a cause of sudden cardiac death in the arrhythmia literature.

Evidence that stun guns can stimulate the heart

Deaths have occurred shortly after stun gun discharges.22 However, association alone does not prove causality. The possible mechanisms of short-term or immediate-term cardiac effects relate to the stimulation of the heart or induction of ventricular fibrillation. Stimulation of the heart is a separate issue compared with induction of arrhythmia, as stimulation may happen only during discharge and may not be evident even immediately following the discharge. In contrast, induction of arrhythmia may relate to stimulation of the heart because, depending on pre-existing defects (e.g., a previous heart attack, drug intoxication), each person's heart may have a different susceptibility to life-threatening arrhythmia during stimulation. Podgorski and colleagues23 found that the direct application of an older version of a stun gun to a pig heart, which was exposed but covered by a towel, produced stimulation of the heart.

Because the theory of electrical stimulation suggests that stun gun discharges should not stimulate the heart, we tested the hypothesis using a closed-chest in vivo animal model.24 A unique feature of our study was that real stun guns were used and operated by qualified law enforcement personnel, which simulated real-world conditions. Two different models (TASER X26 and M26) that deliver different pulse waveforms were used on an anesthetized pig. Recording the electrical activity of the heart is challenging, because the acquisition system is usually completely saturated by the electromagnetic interference generated by the stun gun discharge. However, we found that the pig's arterial blood pressure was occasionally abruptly lost during stimulation. To further verify that this blood pressure modulation was not a recording artifact, we opened the artery to air and found that the pumping of blood stopped during the discharge of the stun gun. This made us suspicious that either an arrhythmia was being induced or the heart was being stimulated so rapidly that it was not capable of producing pulsatile pressure. To test this, we shielded our mapping system and recorded the electrical activity during discharge.

We studied a total of 150 discharges in 6 pigs. Of these, 74 of these discharges resulted in stimulation of the myocardium, as documented electrical capture (a provoked response in the myocardium) (mean ventricular rate during stimulation and capture, 324 [standard error 66] beats/min) (Figure 1). Of the 94 discharges across the heart, 74 stimulated the myocardium. We took care to ensure that the gun barbs did not pierce deep into the tissue. We also placed the barbs such that they were oriented across the heart, simulating the worst case scenario of creating a current vector that directly passes through the heart. If these barbs were placed away from the chest and across the abdomen, none of the 56 discharges across the abdomen stimulated the heart (Figure 2), suggesting that the location of the barbs had a crucial influence on stimulating the heart. We also observed that the waveform (pulse shape) produced by the device affected stimulation, because when we used a different model of the stun gun (TASER M26), we observed a lower incidence of cardiac stimulation.

Figure 1: Cardiac stimulation and hypotension from a stun gun discharge. Note the corruption of the surface electrocardiographic leads in panel B and the electrical activity of the intracardiac electrograms. After stun gun discharge, a spontaneous and immediate return of regular sinus rhythm and blood pressure occurs (panel C). Panel D and E show magnified intracardiac electrograms of similar duration. It is evident in panel E that the rate is much faster and the rhythm is wider than in panel D. The morphology of the tachycardia in panel E is wider than the morphology in panel D. There is a constant stun gun stimulus artifact to electrogram duration as illustrated in panel E, with every fourth stun gun discharge resulting in stimulation of the heart. Note the loss of blood pressure during the stimulation and the recovery of blood pressure once the discharge is completed. Reproduced with permission from Elsevier (Nanthakumar et al24). Note: CS = coronary sinus, RV = right ventricular, BP = blood pressure.

Figure 2: A typical episode of a stun gun shock across the abdomen (nonthoracic vector) that does not result in stimulation of the myocardium. The surface electrocardiogram lead 1, intracardiac electrograms from the coronary sinus, the right ventricle apex and blood pressure in the descending aorta are shown. Panel A illustrates the regular rhythm before the discharge, which is very similar to the rhythm and rate in panel C. The intracardiac electrograms, as illustrated in panels D and E, do not show any significant change in rate morphology and are not phase-locked (no temporal relation between stimuli and the electrogram) with the stun gun discharge. Note also the lack of perturbation of blood pressure during the discharge. Reproduced with permission from Elsevier (Nanthakumar et al24). Note: CS = coronary sinus, RV = right ventricular, BP = blood pressure.

In addition, we simulated an excited state infusing pigs with epinephrine, which renders the myocardium more excitable and prone to arrhythmias. Of 16 discharges, there were 13 episodes of myocardial stimulation, of which 1 induced ventricular fibrillation and 1 caused ventricular tachycardia. In contrast, another study, which simulated an excited stated by infusing cocaine into pigs, did not report induction of ventricular fibrillation during discharge. The main conclusions of this study was that stun gun use in the presence of cocaine does not increase the chance of arrhythmia. However, this study used a waveform simulator, not an actual stun gun, and although ventricular fibrillation was not induced, there was stimulation of the heart.

Three different studies involving pigs, 1 of which was performed by us, have shown that a stun gun discharge can stimulate the heart. In particular, 1 study reported the deaths of 2 animals caused by ventricular fibrillation immediately after the stun gun discharge. This study also reported severe metabolic and respiratory acidosis caused by discharge. This suggests that sufficient current density was produced by the stun gun to stimulate the heart, which according to theory should not occur. A potential explanation of why, despite the theory, stimulation was observed is that there were metallic objects (e.g., catheter or pacemaker leads) inside the heart, which probably carried currents induced by the electromagnetic interference generated during the shock. One could argue that these currents could instead be the primary source of heart stimulation. Because capture could only be observed using intracardiac electrograms, this remains speculative. The fact that in our study we did not observe capture when the stun gun shocks were administered away from the chest suggests that the dart locations play a more important role in stimulation than the presence of metallic objects in the heart. In addition, in our study, we removed all electrical catheters from the heart and still observed the cessation of arterial pumping during discharge. We also confirmed that even without catheters in the heart, stun gun discharges on the chest can stimulate the heart and, at the least, can result in a loss of blood pressure during discharge.

Indeed, a human's chest is different from that of a pig, and there may be differences in electrophysiology between human and pig hearts. One should be prudent in extrapolating data from animals to humans because of this fact. The corollary, though, is that most of the basic mechanistic concepts in cardiac fibrillation and defibrillation are derived from animal studies, not humans. In addition, the safety margins for energy of stun gun discharge established by manufacturers were derived from animal models . 

Researchers from San Francisco recently published the case of a patient with a pacemaker who received a stun gun shock. They observed that discharges from the stun gun provoked a response in the myocardium (Figure 3). It is unknown if this would have occurred without the presence of pacemaker wires, although without these wires, verifying the presence of cardiac capture would not have been possible. In addition, John Webster's research group reported in a conference abstract that stun gun discharges can stimulate the heart.27 Although published theoretical analyses about stun gun safety have scientific merit, we should be aware that theories are only as good as the assumptions and conditions defined based on available data or knowledge.

Figure 3: Magnified summed intracardiac electrograms from a patient's internal pacemaker log during stun gun discharge. Cardiac capture is shown by the high-rate ventricular sensing (cycle length 203–289 milliseconds); the cyclic, low-frequency modulation of high-frequency noise (stun gun pulses) during ventricular sensing; a single, long ventricular interval (648 milliseconds) after the energy stops; and postdischarge resumption of atrial and ventricular sensing at a rate similar to predischarge cardiac rate. The high-frequency pulses (15 pps, 66 milliseconds) are labelled on the tracing. The intracardiac electrograms from the last sensed ventricular event during stun gun application are superimposed on each prior ventricular sensed event, showing that the disruption of the high-frequency stun gun signal is consistent with modulation of the signal by a repeating R wave with morphology different than the intrinsic R wave (right side of the image). Reproduced with permission from Blackwell (Cao et al26).

Explaining the discrepancies between theory and observation

Why have 3 independent groups of investigators reported in peer-reviewed journals that cardiac stimulation can occur when the theory says it cannot happen? Theoretical safety calculations may not hold true if the theory used to calculate the membrane time constant using external pacing parameters (i.e., with large pads that do not break the skin barrier, without rapid stimulation at high voltage) does not apply to stun gun stimulation across the chest wall. Although the membrane constant is usually considered an intrinsic property of cardiac muscle, various studies have measured time constants during human trans-chest pacing from 0.5 milliseconds to 1.1 milliseconds.28 However, another study with direct pacing on dog myocardium reported an average value of 2.4 milliseconds,29 suggesting that the time constant is actually a characteristic of not only the cell membrane but also the stimulator, and the size and the position of the electrode used. This suggests a large variability over the population; thus, an identical pulse with a specific duration and strength could have different stimulation effects on different people.

Over the last century, various studies have been performed on the strength–duration relation of electric impulses and their effect on cardiac stimulation. From some of these studies, it is evident that the assumptions made about membrane time constants and contact electrode sizes strongly influence the outcome.30Typically, electrodes in contact within the myocardium may stimulate with 50 milliamperes when the current is injected over a period of 50 microseconds. However, shorter pulse durations would require a larger amount of current to stimulate the heart. There is a possibility of inducing a lethal cardiac arrhythmias when factors (e.g., strength, duration and frequency of the electric pulses; membrane time constant; contact impedance; and timing of electrical discharge) favour triggering the heart during a vulnerable period of the cardiac cycle.

Knowledge gaps

Although there have been deaths reported following stun gun discharges, this appears to be rare. In addition, some animal studies suggest that stun gun shocks may have cardiovascular effects. Whether the reported deaths were related to the external shocks is unknown. It is also unknown whether cardiac stimulation occurs only during discharge. The observational studies involving human volunteers thus far could be considered phase I studies because they relate mainly to tolerability and do not prove the safety of the devices. It is very important that tolerability should not be misconstrued as safety. The largest knowledge gap is the lack of appropriate studies involving humans to establish the safety margins for stun gun shock energies when the vector of discharge is across the heart.

The effects of potential modifying factors such as sex, body mass, cardiac and noncardiac diseases, alcohol, medications and psychotropic drugs also need to be evaluated. It is evident that psychotropic drugs such as cocaine heighten the sympathetic state in animal studies. The effect of these drugs and their influence on human autonomic physiology during stun gun discharges is an important aspect that needs urgent evaluation.

Conclusions

Despite many studies suggesting that stun guns do not affect the heart, the evidence and studies presented in this review suggest that, in some circumstances, stun guns may stimulate the heart while discharges are being applied. However, there is no conclusive evidence to show whether stun gun stimulation (under certain electrophysiological conditions) can result in cardiac arrhythmias late after stun gun discharge. In our view, it is inappropriate to conclude that stun gun discharges cannot lead to adverse cardiac consequences in all real world settings.

We believe that the findings that stun gun discharges are able, under specific circumstances, to stimulate the heart should be taken into account in future studies involving people. Whether stun guns can stimulate the heart can only be established if one can record electrical activity in the heart during a discharge, especially when the vector of discharge is directed across the heart. Additional research studies involving people will help to resolve the conflicting theoretical and experimental findings, and they could lead to the design of devices with electrical pulses that cannot stimulate the heart.

                                       XXX  .  XXX  Directed-energy weapon

A directed-energy weapon (DEW) is a ranged weapon system that inflicts damage at a target by emission of highly focused energy, including laser, microwaves and particle beams. Potential applications of this technology include anti-personnel weapon systems, missile defense system, and the disabling of lightly armored vehicles or mounted optical devices.

In the United States, the Pentagon, DARPA, the Air Force Research Laboratory, United States Army Armament Research Development and Engineering Center, and the Naval Research Laboratory are researching technologies like directed-energy weapons and railguns to counter maturing threats posed by fast missiles such as ballistic missiles, hypersonic cruise missiles, and hypersonic glide vehicles. These systems of missile defense are expected to come online in the mid to late-2020s or later. Russia,China,India, and the United Kingdom are also developing directed-energy weapons.

After decades of R&D, directed-energy weapons are still very much at the experimental stage and it remains to be seen if or when they will be deployed as practical, high-performance military weapons

Operational advantages

Directed energy weapons could have several main advantages over conventional weaponry:

• Direct energy weapons can be used discreetly as radiation above and below the visible spectrum is invisible and does not generate sound.
• Light is only very slightly altered by gravity, giving it an almost perfectly flat trajectory. It is also practically immune (in anything resembling normal planetary conditions) to both windage and Coriolis force. This makes aim much more precise and extends the range to line-of-sight, limited only by beam diffraction and spread (which dilute the power and weaken the effect), and absorption or scattering by intervening atmospheric contents.
• They can have much greater speed and range than conventional weapons, therefore, are suitable for use in space warfare.

Types

Microwave weapons

Although some devices are labelled as microwave weapons, the microwave range is commonly defined as being between 300 MHz and 300 GHz which is within the RF range —these frequencies having wavelengths of 1–1000 micrometers. Some examples of weapons which have been publicized by the military are as follows:

• Active Denial System is a millimeter wave source that heats the water in a human target's skin and thus causes incapacitating pain. It was developed by the U.S. Air Force Research Laboratory and Raytheon for riot-control duty. Though intended to cause severe pain while leaving no lasting damage, concern has been voiced as to whether the system could cause irreversible damage to the eyes. There has yet to be testing for long-term side effects of exposure to the microwave beam. It can also destroy unshielded electronics.^[22] The device comes in various sizes including attached to a humvee.
• Vigilant Eagle is a proposed airport defense system that directs high-frequency microwaves towards any projectile that is fired at an aircraft. The system consists of a missile-detecting and tracking subsystem (MDT), a command and control system, and a scanning array. The MDT is a fixed grid of passive infrared (IR) cameras. The command and control system determines the missile launch point. The scanning array projects microwaves that disrupt the surface-to-air missile's guidance system, deflecting it from the aircraft.
• Bofors HPM Blackout is a high-powered microwave weapon system which is stated to be able to destroy at short distance a wide variety of commercial off-the-shelf (COTS) electronic equipment. It is stated to be not lethal to humans.
• The effective radiated power (ERP) of the EL/M-2080 Green Pine radar makes it an hypothetical candidate for conversion into a directed-energy weapon, by focusing pulses of radar energy on target missiles.^[28] The energy spikes are tailored to enter missiles through antennas or sensor apertures where they can fool guidance systems, scramble computer memories or even burn out sensitive electronic components.
• AESA radars mounted on fighter aircraft have been slated as directed energy weapons against missiles, however, a senior US Air Force officer noted: "they aren't particularly suited to create weapons effects on missiles because of limited antenna size, power and field of view".^[29] Potentially lethal effects are produced only inside 100 metres range, and disruptive effects at distances on the order of one kilometre. Moreover, cheap countermeasures can be applied to existing missiles.

Laser weapons

Electrolaser

An electrolaser first ionizes its target path, and then sends a powerful electric current down the conducting track of ionized plasma, somewhat like lightning. It functions as a giant, high-energy, long-distance version of the Taser or stun gun.

Pulsed energy projectile

Pulsed Energy Projectile or PEP systems emit an infrared laser pulse which creates rapidly expanding plasma at the target. The resulting sound, shock and electromagnetic waves stun the target and cause pain and temporary paralysis. The weapon is under development and is intended as a non-lethal weapon in crowd control though it can also be used as a lethal weapon.

Dazzler

A dazzler is a directed-energy weapon intended to temporarily blind or disorient its target with intense directed radiation. Targets can include sensors or human vision. Dazzlers emit infrared or invisible light against various electronic sensors, and visible light against humans, when they are intended to cause no long-term damage to eyes. The emitters are usually lasers, making what is termed a laser dazzler. Most of the contemporary systems are man-portable, and operate in either the red (a laser diode) or green (a diode-pumped solid-state laser, DPSS) areas of the electromagnetic spectrum.

Initially developed for military use, non-military products are becoming available for use in law enforcement and security.

PHASR Rifle

The personnel halting and stimulation response rifle (PHASR) is a prototype non-lethal laser dazzler developed by the Air Force Research Laboratory's Directed Energy Directorate, U.S. Department of Defense.^[33] Its purpose is to temporarily disorient and blind a target. Blinding laser weapons have been tested in the past, but were banned under the 1995 United Nations Protocol on Blinding Laser Weapons, which the United States acceded to on 21 January 2009.^[34] The PHASR rifle, a low-intensity laser, is not prohibited under this regulation, as the blinding effect is intended to be temporary. It also uses a two-wavelength laser.^[35] The PHASR was tested at Kirtland Air Force Base, part of the Air Force Research Laboratory Directed Energy Directorate in New Mexico.

• ZM-87
• PY132A is a Chinese anti-drone dazzler.
• Soviet laser pistol was a prototype weapon designed for cosmonauts.

Laser weapon examples

• Project Excalibur was a United States government nuclear weapons research program to develop a nuclear pumped x-ray laser as a directed energy weapon for ballistic missile defence.^[37] Cancelled.
• In 1984 the Soviet Strategic Missile Troops military academy developed the first handheld laser weapon, intended for use by cosmonauts in outer space. No longer used.
• 1K17 Szhatie- Experimental Soviet self-propelled laser weapon. Never went beyond the experimental stage.
• In 1987 a Soviet laser-armed orbital weapon system, the 17F19DM Polyus/Skif-DM, failed during deployment.
• In 1991 scientists at the US Army Missile Command developed and field tested a ruggedized tunable laser emitting in yellow-orange-red part of the spectrum.^[38] Never went beyond the experimental stage.
• Made by Northrop Grumman:
  • On March 18, 2009 Northrop Grumman announced that its engineers in Redondo Beach had successfully built and tested an electric laser capable of producing a 100-kilowatt ray of light, powerful enough to destroy cruise missiles, artillery, rockets and mortar rounds.^[39] An electric laser is theoretically capable, according to Brian Strickland, manager for the United States Army's Joint High Power Solid State Laser program, of being mounted in an aircraft, ship, or vehicle because it requires much less space for its supporting equipment than a chemical laser.^[40] Experimental.
  • On April 6, 2011, the U.S. Navy successfully tested a laser gun, manufactured by Northrop Grumman, that was mounted on the former USS Paul Foster, which is currently used as the navy's test ship. When engaged during the test that occurred off the coast of Central California in the Pacific Ocean test range, the laser gun was documented as having "a destructive effect on a high-speed cruising target", said Chief of Naval Research Admiral Nevin Carr.^[41] While classified, the proposed range of the laser gun is measured in miles, not yards. Experimental.
  • Northrop Grumman has announced the availability of a high-energy solid-state laser weapon system that they call FIRESTRIKE, introduced on 13 November 2008. The system is modular, using 15 kW modules that can be combined to provide various levels of power. Experimental.
  • Skyguard (area defense system). Proposed.
• Boeing YAL-1. Discontinued.
• Precision Airborne Standoff Directed Energy Weapon. Cancelled.
• On 19 July 2010 an anti-aircraft laser described as the Laser Close-In Weapon System was unveiled at the Farnborough Airshow.^[42] Experimental.
• The ZEUS-HLONS (HMMWV Laser Ordnance Neutralization System) is the first laser and the first energy weapon of any type to be used on a battlefield. It is used for neutralizing mines and unexploded ordnance. Niche application.
• High Energy Liquid Laser Area Defense System (HELLADS). Status unknown.
• The Mid-Infrared Advanced Chemical Laser (MIRACL) is an experimental U.S. Navy deuterium fluoride laser and was tested against an Air Force satellite in 1997. Cancelled.
• In 2011, the U.S. Navy began to test the Maritime Laser Demonstrator (MLD), a laser for use aboard its warships.^[43][44] Status unknown.
• In 2013 the U.S. began field testing a directed-energy weapon it calls the Laser Weapon System.^[45] Experimental.
• Personnel Halting and Stimulation Response, or PHaSR, is a non-lethal hand-held weapon developed by the United States Air Force^[46] Its purpose is to "dazzle" or stun a target. It was developed by Air Force's Directed Energy Directorate. Status unknown.
• Tactical High Energy Laser (THEL) is a weaponized deuterium fluoride laser developed in a joint research project by Israel and the U.S. It is designed to shoot down aircraft and missiles. See also National missile defense. Discontinued.
• Soviet/Russian Beriev A-60: a CO₂ gas laser mounted on an Ilyushin Il-76MD transport. Experimental.
• The U.S. Air Force's Airborne Laser, or Advanced Tactical Laser, was a plan to mount a CO2 gas laser or COIL chemical laser on a modified Boeing 747 to shoot down missiles.^[47][48] Cancelled.
• High Energy Laser-Mobile Demonstrator (HEL-MD) is a Boeing designed laser system mounted on a Heavy Expanded Mobility Tactical Truck (HEMTT). Its current power level is 10 kW, which will be boosted to 50 kW, and expected to eventually be upgraded to 100 kW. Targets that can be engaged are mortar rounds, artillery shells and rockets, unmanned aerial vehicles, and cruise missiles.^[49] Status unknown.
• Lockheed Martin is developing a 60 kW fiber laser to mount on the HEMTT that maintains beam quality at high power outputs while using less electricity than solid-state lasers. Status unknown.
• Free-electron laser (FEL) technology is being evaluated by the US Navy as a candidate for an antiaircraft and anti-missile directed-energy weapon. The Thomas Jefferson National Accelerator Facility's FEL has demonstrated over 14 kW power output.^[53]Compact multi-megawatt class FEL weapons are undergoing research.^[54] On June 9, 2009 the Office of Naval Research announced it had awarded Raytheon a contract to develop a 100 kW experimental FEL.^[55] On March 18, 2010 Boeing Directed Energy Systems announced the completion of an initial design for U.S. Naval use.^[56] A prototype FEL system was demonstrated, with a full-power prototype scheduled by 2018.^[57] Experimental.
• Portable Efficient Laser Testbed (PELT)^[58] Status unknown.
• Laser AirCraft CounterMeasures (ACCM)^[59] Status unknown.
• Mobile Expeditionary High-Energy Laser (MEHEL) 2.0 Experimental.
• Area Defense Anti-Munitions (ADAM)^[62] Experimental.
• Advanced Test High Energy Asset (ATHENA)^[63] Status unknown.
• Self-Protect High-Energy Laser Demonstrator (SHiELD). Pre-prototype stage.
• Silent Hunter (laser weapon)^[64] is a Chinese fibre optic laser air-defence system. Status unknown.
• See also Electrolaser#Examples of electrolasers.
• Russian Sokol Eshelon. Experimental.
• Raytheon Company announced that it developed a high-energy laser that can be mounted on a MRZR and used to disable an unmanned aerial system from approximately 1 mile away. Status unknown.

Most of these projects have been cancelled, discontinued, never went beyond the prototype or experimental stage, or are only used in niche applications. Effective, high performance laser weapons seem to be difficult to achieve using current or near-future technology.

Problems with laser weapons

Blooming

Laser beams begin to cause plasma breakdown in the atmosphere at energy densities of around one megajoule per cubic centimetre. This effect, called "blooming," causes the laser to defocus and disperse energy into the surrounding air. Blooming can be more severe if there is fog, smoke, or dust in the air.

Techniques that may reduce these effects include:

• Spreading the beam across a large, curved mirror that focuses the power on the target, to keep energy density en route too low for blooming to happen. This requires a large, very precise, fragile mirror, mounted somewhat like a searchlight, requiring bulky machinery to slew the mirror to aim the laser.
• Using a phased array. For typical laser wavelengths, this method would require billions of micrometre-size antennae. There is currently no known way to implement these, though carbon nanotubes have been proposed. Phased arrays could theoretically also perform phase-conjugate amplification (see below). Phased arrays do not require mirrors or lenses, and can be made flat and thus do not require a turret-like system (as in "spread beam") to be aimed, though range will suffer if the target is at extreme angles to the surface of the phased array.
• Using a phase-conjugate laser system. This method employs a "finder" or "guide" laser illuminating the target. Any mirror-like ("specular") points on the target reflect light that is sensed by the weapon's primary amplifier. The weapon then amplifies inverted waves, in a positive feedback loop, destroying the target, with shockwaves as the specular regions evaporate. This avoids blooming because the waves from the target pass through the blooming, and therefore show the most conductive optical path; this automatically corrects for the distortions caused by blooming. Experimental systems using this method usually use special chemicals to form a "phase-conjugate mirror". In most systems, the mirror overheats dramatically at weapon-useful power levels.
• Using a very short pulse that finishes before blooming interferes.
• Focusing multiple lasers of relatively low power on a single target.

Countermeasures

The Chinese People's Liberation Army has invested in the development of coatings that can deflect beams fired by U.S. military lasers. Lasers are composed of light that can be deflected, reflected, or absorbed by manipulating physical and chemical properties of materials. Artificial coatings can counter certain specific types of lasers, but a different type of laser may match the coating's absorption spectrum enough to transfer damaging amounts of energy. The coatings are made of several different substances, including low-cost metals, rare earths, carbon fiber, silver, and diamonds that have been processed to fine sheens and tailored against specific laser weapon systems. China is developing anti-laser defenses because protection against them is considered far cheaper than creating competing laser weapons themselves. Apart from creating countermeasures, China has also created a direct-energy weapon called the Silent Hunter that can burn through 5mm of steel at 1000m.

Dielectric mirrors, inexpensive ablative coatings, thermal transport delay and obscurants are also being studied as countermeasures. In not a few operational situations, even simple, passive countermeasures like rapid rotation (which spreads the heat and doesn't allow a fixed targeting point) or higher acceleration (which increases the distance and changes the angle quickly) can defeat or help to defeat non-highly pulsed, high energy laser weapons.

Particle-beam weapons

Particle-beam weapons can use charged or neutral particles, and can be either endoatmospheric or exoatmospheric. Particle beams as beam weapons are theoretically possible, but practical weapons have not been demonstrated yet. Certain types of particle beams have the advantage of being self-focusing in the atmosphere.

Blooming is also a problem in particle-beam weapons. Energy that would otherwise be focused on the target spreads out; the beam becomes less effective:

• Thermal blooming occurs in both charged and neutral particle beams, and occurs when particles bump into one another under the effects of thermal vibration, or bump into air molecules.
• Electrical blooming occurs only in charged particle beams, as ions of like charge repel one another.

Plasma weapons

Plasma weapons fire a beam, bolt, or stream of plasma, which is an excited state of matter consisting of atomic electrons & nuclei and free electrons if ionized, or other particles if pinched.

The MARAUDER (Magnetically Accelerated Ring to Achieve Ultra-high Directed-Energy and Radiation) used the Shiva Star project (a high energy capacitor bank which provided the means to test weapons and other devices requiring brief and extremely large amounts of energy) to accelerate a toroid of plasma at a significant percentage of the speed of light.

The Russian Federation is developing plasma weapons.

Sonic weapons

Cavitation, which affects gas nuclei in human tissue, and heating can result from exposure to ultrasound and can damage tissue and organs. Studies have found that exposure to high intensity ultrasound at frequencies from 700 kHz to 3.6 MHz can cause lung and intestinal damage in mice. Heart rate patterns following vibroacoustic stimulation have resulted in serious arterial flutter and bradycardia. Researchers have concluded that generating pain through the auditory system using high intensity sound risked permanent hearing damage.

A multi-organization research program involved high intensity audible sound experiments on human subjects. Extra-aural (unrelated to hearing) bioeffects on various internal organs and the central nervous system included auditory shifts, vibrotactile sensitivity change, muscle contraction, cardiovascular function change, central nervous system effects, vestibular (inner ear) effects, and chest wall/lung tissue effects. Researchers found that low frequency sonar exposure could result in significant cavitations, hypothermia, and tissue shearing. Follow-on experiments were not recommended.

Tests performed on mice show the threshold for both lung and liver damage occurs at about 184 dB. Damage increases rapidly as intensity is increased. Noise-induced neurological disturbances in humans exposed to continuous low frequency tones for durations longer than 15 minutes involved development of immediate and long-term problems affecting brain tissue. The symptoms resembled those of individuals who had suffered minor head injuries. One theory for a causal mechanism is that the prolonged sound exposure resulted in enough mechanical strain to brain tissue to induce an encephalopathy.

Long Range Acoustic Device (LRAD)

The LRAD is the round black device on top of the New York City police Hummer.

The Long Range Acoustic Device (LRAD) is an acoustic hailing device developed by LRAD Corporation to send messages and warning tones over longer distances or at higher volume than normal loudspeakers. LRAD systems are used for long range communications in a variety of applications^[77] including as a means of non-lethal, non-kinetic crowd control.

According to the manufacturer's specifications, the systems weigh from 15 to 320 pounds (6.8 to 145.1 kg) and can emit sound in a 30°- 60° beam at 2.5 kHz.

Flash Back

Mirrors of Archimedes

Archimedes may have used mirrors acting collectively as a parabolic reflector to burn ships attacking Syracuse.

According to a legend, Archimedes created a mirror with an adjustable focal length (or more likely, a series of mirrors focused on a common point) to focus sunlight on ships of the Roman fleet as they invaded Syracuse, setting them on fire.^[79] Historians point out that the earliest accounts of the battle did not mention a "burning mirror", but merely stated that Archimedes's ingenuity combined with a way to hurl fire were relevant to the victory. Some attempts to replicate this feat have had some success; in particular, an experiment by students at MIT showed that a mirror-based weapon was at least possible, if not necessarily practical.

Robert Watson-Watt

The fictional "engine-stopping ray"

Stories in the 1930s and World War Two gave rise to the idea of an "engine-stopping ray". They seemed to have arisen from the testing of the television transmitter in Feldberg, Germany. Because electrical noise from car engines would interfere with field strength measurements, sentries would stop all traffic in the vicinity for the twenty minutes or so needed for a test. Reversing the order of events in retelling the story created a "tale" where tourists car engine stopped first and then were approached by a German soldier who told them that they had to wait. The soldier returned a short time later to say that the engine would now work and the tourists drove off. Such stories were circulating in Britain around 1938 and during the war British Intelligence relaunched the myth as a "British engine-stopping ray", trying to spoof the Germans into researching what the British had invented in an attempt to tie up German scientific resources.

German World War II experimental weapons

During the early 1940s Axis engineers developed a sonic cannon that could cause fatal vibrations in its target body. A methane gas combustion chamber leading to two parabolic dishes pulse-detonated at roughly 44 Hz. This sound, magnified by the dish reflectors, caused vertigo and nausea at 200–400 metres (220–440 yd) by vibrating the middle ear bones and shaking the cochlear fluid within the inner ear. At distances of 50–200 metres (160–660 ft), the sound waves could act on organ tissues and fluids by repeatedly compressing and releasing compressive resistant organs such as the kidneys, spleen, and liver. (It had little detectable effect on malleable organs such as the heart, stomach and intestines.) Lung tissue was affected at only the closest ranges as atmospheric air is highly compressible and only the blood rich alveoli resist compression. In practice, the weapon system was highly vulnerable to enemy fire. Rifle, bazooka and mortar rounds easily deformed the parabolic reflectors, rendering the wave amplification ineffective.

In the later phases of World War II, Nazi Germany increasingly put its hopes on research into technologically revolutionary secret weapons, the Wunderwaffen.

Among the directed-energy weapons the Nazis investigated were X-ray beam weapons developed under Heinz Schmellenmeier, Richard Gans and Fritz Houtermans. They built an electron accelerator called Rheotron (invented by Max Steenbeck at Siemens-Schuckert in the 1930s, these were later called Betatrons by the Americans) to generate hard X-ray synchrotron beams for the Reichsluftfahrtministerium (RLM). The intent was to pre-ionize ignition in aircraft engines and hence serve as anti-aircraft DEW and bring planes down into the reach of the FLAK. The Rheotron was captured by the Americans in Burggrub on April 14, 1945.

Another approach was Ernst Schiebolds 'Röntgenkanone' developed from 1943 in Großostheim near Aschaffenburg. The Company Richert Seifert & Co from Hamburg delivered parts.

Reported use in Sino-Soviet conflicts

The Central Intelligence Agency informed Secretary Henry Kissinger that it had twelve reports of Soviet forces using laser-based weapons against Chinese forces during the 1969 Sino-Soviet border clashes, though William Colby doubted that they had actually been employed.

Strategic Defense Initiative

In the 1980s, U.S. President Ronald Reagan proposed the Strategic Defense Initiative (SDI) program, which was nicknamed Star Wars. It suggested that lasers, perhaps space-based X-ray lasers, could destroy ICBMs in flight. Panel discussions on the role of high-power lasers in SDI took place at various laser conferences, during the 1980s, with the participation of noted physicists including Edward Teller.

Though the strategic missile defense concept has continued to the present under the Missile Defense Agency, most of the directed-energy weapon concepts were shelved. However, Boeing has been somewhat successful with the Boeing YAL-1 and Boeing NC-135, the first of which destroyed two missiles in February 2010. Funding has been cut to both of the programs.

Alleged tracking of Space Shuttle Challenger

The Soviet Union invested some effort in the development of ruby and carbon dioxide lasers as anti-ballistic missile systems, and later as a tracking and anti-satellite system. There are reports that the Terra-3 complex at Sary Shagan was used on several occasions to temporarily "blind" US spy satellites in the IR range.

It has been claimed (and proven false) that the USSR made use of the lasers at the Terra-3 site to target the Space Shuttle Challenger in 1984. At the time, the Soviet Union were concerned that the shuttle was being used as a reconnaissance platform. On 10 October 1984 (STS-41-G), the Terra-3 tracking laser was allegedly aimed at Challenger as it passed over the facility. Early reports claimed that this was responsible for causing "malfunctions on the space shuttle and distress to the crew", and that the United States filed a diplomatic protest about the incident. However, this story is comprehensively denied by the crew members of STS-41-G and knowledgeable members of the US intelligence community.

Planetary defense

In the United States, the Directed Energy Solar Targeting of Asteroids and exploRation (DE-STAR) Project was considered for non-military use to protect Earth from asteroids.

Non-lethal weapons

The TECOM Technology Symposium in 1997 concluded on non-lethal weapons, "determining the target effects on personnel is the greatest challenge to the testing community", primarily because "the potential of injury and death severely limits human tests".

Also, "directed energy weapons that target the central nervous system and cause neuro physiological disorders may violate the Certain Conventional Weapons Convention of 1980. Weapons that go beyond non-lethal intentions and cause "superfluous injury or unnecessary suffering" may also violate the Protocol I to the Geneva Conventions of 1977."

Some common bio-effects of non-lethal electromagnetic weapons include:

• Difficulty breathing
• Disorientation
• Nausea
• Pain
• Vertigo
• Other systemic discomfort.

Interference with breathing poses the most significant, potentially lethal results.

Light and repetitive visual signals can induce epileptic seizures. Vection and motion sickness can also occur.

Cruise ships are known to use sonic weapons (such as LRAD) to drive off pirates.

                                   XXX  .  XXX 4% zero null 0 Laser Gun Circuit

              

                      

                 Simple Electric Shock Gun Circuit Diagram 

  

                                                  Taser Gun Circuit

                                                

                                                 

we have created this Instruct able for those with NO electronic knowledge on how to create a laser gun. This is more like a laser pointer though, but thats what happens when you leave out all those fun little parts.

Step 1 : 

laser
wire
momentary push button switch(make sure its easy to press)
solder
soldering gun(no precision tip needed)
hot glue
hot glue gun
9 volt battery
9 volt battery hook-up
click on, click off switch(optional, make sure its easy to press)
LED(optional)
2 AA batteries(goes with led)
2 AA battery holder(goes with the led)

Most of this stuff you can get at radio shack except for the laser and hot glue . 

                 

We remember, red wire is positive, and black wire is negative.  Leave enough room with the wire to be able to play with it some when you put it inside the gun.  We added an led because We felt like it needed something besides just a laser (also there was a second hole in my gun). My led was blue, which meant that it could handle 3 volts of power, but if you want a different color, you may have to use a resistor.  Make sure to solder the momentary push button switch to the laser and 9 volt battery and laser, and please, test before you solder. The click on, click off switch you can soler to the led and 3 volts of power(The flat end of the led is the negative end if you did not already know that). 

Step 3 : 

   

Screw open the Nerf gun and gut it. Save the screws that hold the shell and cocking handle together. Now use a lot of hot glue to hold everything where you want it.  like the push button switch in a place it will be pushed by the trigger and the click on, click off switch where it will be pushed by the cocking mechanism. 

Step 4 : Closing Your Blessed Blaster

Step 5:

And there you have it!  A laser gun from a Nerf gun.  Now you can ether blast those storm troopers back or impress you colleges with you awesome laser pointer.

                XXX  .  XXX 4%zero null 0 1 2 3 4  ENERGY WEAPON SIDEARMS

  

Various real-world militaries are trying to develop actual combat lasers, under the term Directed Energy Weapn (DEW). Which sounds so much more pragmatic than "ray gun". 

The main advantages of laser weapons include: weapon bolt travels at the speed of light, excellent accuracy, damage inflicted by the bolt can be dialed up or down, lasers have no recoil, and the "ammunition" (i.e., electricity required per bolt) is much more inexpensive than the equivalent conventional bullet.

The main disadvantages of laser weapons include: it still requires huge amounts of power, bullet ammo takes up far less space than power generators, it has far more of a waste heat problem than a conventional firearm, and the energy in a given bolt is severely reduced by dust, smoke, clouds, or rain.

The main advantage of particle beam weapons is they have penetration that make lasers look like throwing a handfull of thistledown.

The main drawbacks of particle beam weapons is they are power hogs, they are difficult to reduced to pistol size, and Terra's atmosphere will scatter enough of the beam to give the firer a lethal dose of radiation.

Lasers

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  Colonial laser pistol, Battlestar Galactica (1978). Note recharge plug on side, power gauges on top. I think the cylindrical emitter can move back and forth on the track in order to focus the beam.

First a safety note. Pretty much zero science fiction stories, movies, or TV shows mention that laser sidearms have the ability to permanently blind anybody closer to the weapon than the horizon. If the beam is in the frequencies that can penetrate the cornea of the eye, and the beam reflects off a door nob or other mirrored surface, anybody whose eyes get flashed by the beam is going to need a seeing-eye dog.

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"Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. A laser beam can cut through steel while a flashlight cannot due to the fact that laser light is coherent. This means all the photons in the beam are marching in lock-step with each other, instead of every-which-way like ordinary light. By analogy, a unit of army troops marching in step can inadvertently cause a bridge to collapse, while the same number of people using the bridge in a random fashion have no effect.
For details about how lasers are generated, read the details in the link above. An important fact to note is that the laser generator has to be "pumped" by filling it with a higher energy/shorter wavelength compared to the laser beam that will emerge. You cannot pump it with the same wavelength as the result beam, or the act of pumping the laser will simultaneously stimulate emission, and you'll never get anywhere.
Also note that you can run the result beam through certain materials to do tricks like frequency doubling. This will allow one to send a 1064 nm infrared laser beam (from a Nd:YAG laser) thorugh a lithium triborate frequency doubler and turn it into a 532 nm green laser beam.
 There is a list of various real-world lasers and their lasing frequencies .

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From a science fictional standpoint, Dr. Campbell is of the opinion that laser weapons will fall into three broad catagories:

Heat Rays

Lasers that shines a beam of near constant power on its target for a prolonged period of time (from a few hundredths of a second or more).
As a weapon they are not as efficient as a blaster, and they do damage more slowly. They are sort of a futuristic flame thrower or acetylene torch. Heat rays use frequencies longer than 200 nanometers: visible light and infrared.

Blasters

Lasers that emit a pulse of light so intense that it causes the matter it hits to violently explode.
A stream of pulses comprising a single laser bolt is the key to making a laser inflict bullet levels of damage. Blasters use frequencies longer than 200 nanometers: visible light and infrared.

Ray Beams

Lasers that emit needle-thin beams that produce a white-hot plasma along their path and easily burn deep holes into their targets.
The main difference between ray beams and other lasers such as heat-rays or blasters is that they use extreme-ultraviolet, x-rays, or gamma-ray frequencies instead of visible light frequencies. In other words, they use "vacuum frequencies", those frequencies shorter than 200 nanometers which are readily absorbed by Terra's atmosphere. As a side note, anything shorter than 10 nanometers is what scientists call "ionizing radiation" and everybody else calls "OMG We're All Freaking Gonna Die deadly nuclear radiation".
Oddly enough, while vacuum frequencies are absorbed by Terra's atmosphere they are not effected by plasmas. Which is the exact opposite with respect to non-vacuum frequency laser beams. This means that you do not have to pulse vacuum frequency lasers in order to have bullet levels of damage.

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Dr. Schilling does not think the laser pistol is as far fetched as most believe. Erik points out that the problem with a man-portable laser pistol would be the power source. Kinetic weapons are probably going to outperform beam weapons for man-portable sidearms for a long time.

Dr. Schilling's analysis

I'll assume a 50-year time frame with no particular haste in developing directed-energy small arms and no fundamental breakthroughs. Only technology currently on the drawing board, in however limited a form, is allowed, but in 50 years expect today's crude laboratory demos to be refined, mature technologies.
I'll also use a standard military or police service handgun as the baseline - you can easily extrapolate down to a compact pistol or up to a small submachine gun-equivalent if you like, but going up to rifle or heavy-weapon scales is a bit trickier.
There are four basic technological approaches I would consider based on my personal knowledge, all of which would lead to similar end results if they worked at all.

Phase-locked diode laser arrays

Lots of microlasers on a chip, all working together. Extremely efficient, if you can actually get them to work together.

Diode-pumped YAG lasers

Lots of microlasers on a chip, each working alone. They won't produce a good beam that way, but if you tune them to the right absorption band and direct them all into a YAG crystal, you can get the latter to lase quite efficiently.

Pulsed linear induction accelerators

Fairly conventional technology for producing high-energy, high-current electron beams with external magnetic fields. This one will need to be pushed right up to the theoretical limits to work on a handgun scale, and it will need an unconventional electron source such as a pseudospark discharge.

Wake field accelerators

Clever way of producing high-energy electron beams using the internal electric fields of forced plasma waves. Still in it's infancy, potential unknown but may well be adequate in the long run.

Dr. Schilling

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  Phased Plasma Gun, Babylon 5 (1994).

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  Klingon sonic disrupter, Star Trek (1967).

Heat Ray

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  From Star Trek "A Private Little War" (1968). Dr. McCoy uses a phaser to turn rocks into impromptu campfires.

A heat ray is a lasers that shines a beam of near constant power on its target for a prolonged period of time (from a few hundredths of a second or more). It uses non-vacuum frequencies, wavelengths longer than 200 nanometers (visible light and infrared). Andre Norton called them "flamers."
In other words they are like flame-throwers with no flame, just the intense heat.
Engineering-wise it is much easier to make a heat ray than a blaster. The latter requires complicated electronics to create the precise laser pulse trains, heat rays just need an on/off switch. But heat rays waste lots of energy by their brute force approach. As soon as the beam hits the target, the target emits a plume of plasma that jets right into the beam path. The beam wastes large amounts of energy burning through the plasma plume before it reaches the target to do further damage. Which makes a fresh plume of plasma. Blasters use a clever technique to avoid this.
This is bad since laser weapons already have a big problem trying to squeeze a worthwhile power source into something man-portable. The inefficient use of laser energy by heat rays means the power source has to be bigger or it has to contain less laser-time before it runs dry. Or both.
In a workshop, heat rays can be used like an acetylene torch.
In battle they can be used much like flame throwers, along with the drawback of making the user into the enemy's priority target. If the enemy soldiers see see a bunch of you guys going pop-pop with rifles, and one of you with a ravening inferno beam of death turning enemy soldiers into barbecued corpses, which one of you do you think the enemy is going to shoot at? Historically soldiers armed with flame throwers had an average life-span on the battlefield of about four minutes (the technical term is "bullet magnet"). Granted, part of that mortality is due to walking around a flying bullet infested battlefield with a big vulnerable tank of gasoline strapped to your back, but still. So a soldier armed with a heat ray might survive for five minutes instead of only four.
The illuminated surface of the target is heated up hot enough to cause softening, warping, blistering, cracking, charring, cooking, ignition, melting, or vaporization. The ray instantly scorches or ignites the surface but takes a bit of time to burn through to the inner layers. Which means heat rays have problems with armored targets. Even an unarmored target can avoid damage by jumping out of the way when they feel the pain. The target can also protect itself by spinning or turning. This constantly puts fresh armor or surface layers into the path of the heat ray, forcing it to start back at square one.
Heat rays are very ineffiicent weapons, unless they have a wide spot size in order to hose wide areas as a futuristic flame-thrower. Alternatively they could be set to raster-scan the beam over the target's body.

 If you want to go that route, for a flash lasting from a fraction of a second and several seconds:

Energy density	Injury
10 J/cm2 to 20 J/cm2	First Degree Burns: Epidermis damage.
20 J/cm2 to 35 J/cm2	Second Degree Burns: Damage extends into partial dermis.
35 J/cm2 to 50 J/cm2	Third Degree Burns: Damage extends through entire dermis.
> 50 J/cm2	Fourth Degree Burns: Damage extends to muscle below dermis.
125 J/cm2	Exposed hair and clothing burst into flame
400 J/cm2	Exposed flesh flashes into steam, flaying exposed body areas to the bone

Equation to calculate energy density can be found here.
First degree burns cause pain. Second or third degree burns covering more than 15% of the body will likely result in death of not given medical attention, incapacitation will be rapid and shock will occure within minutes. Skin color significantly affects susceptibility, light skin being less prone to burns. The table above assumes medium skin color.
Percentage of skin burnt can be estimated by the rule of nines. Since heat-ray victims will only be irradiated on the side facing the ray, the percentages below should be halved.

Adult

Anatomic structure	Surface area
Anterior head	4.5%
Posterior head	4.5%
Anterior torso	18%
Posterior torso	18%
Anterior leg, each	9%
Posterior leg, each	9%
Anterior arm, each	4.5%
Posterior arm, each	4.5%
Genitalia/perineum	1%

A heat ray with a 60 centimeter diameter spot size on the target will cover the torso of an average adult human, irradiating 20% of the body with one flash. The spot area wil l be about 3000 square centimeters. To irradiate that area with 128 J/cm² will take a whopping 384 kilojoules (128 * 3000 = 384,000).
Luke Campbell says "It is not very energy efficient compared to a bullet, but if batteries or fuel are cheap or lightweight or convenient it might still be better overall (after all, bullets are not energy efficient compared to an arrow, but we still use them)."

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Luke Campbell wants to make clear that while "heat-ray" is a vivid name, according to physics it is not actually a ray composed of heat. It is a ray that heats what it illuminates.

Blaster

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  Han Solo's Blaster Pistol, Star Wars: Episode IV (1977). Replica from The Wook's Workshop. As in the movie, this is a broomhandle Mauser with a flash suppressor and an azimuth finding scope.

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  Luke Skywalker's Blaster Pistol, Star Wars: Episode V (1980). Replica from John's Spot on the Web. This one is also a broomhandle Mauser.

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  B is for Blaster

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  Assault Phaser

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  Phaser Rifle, Star Trek (1966).

The key to making a laser do bullet levels of damage is pulsing the laser. This is what distinguishes Luke Campbell's "blasters" from other kinds of lasers.
Consider a laser beam striking an evil Asteroid Pirate. The beam strikes human flesh, turning the water of a thin layer of skin into plasma (ionized gas, not blood transfusion supplies). Where does the plasma go? Mostly into a jet aimed right back at the laser beam.
The jet of plasma partially shields the Asteroid Pirate from the rest of the laser beam. The beam has to waste energy to burn through the cloud of plasma, which reduces the amount of energy actually hitting the asteroid pirate.
{Note this only happens with laser frequencies longer than 200 nanometers: visible light and infrared which are strongly absorbed by plasma. Laser frequencies shorter than 200 nanameters (extreme-ultraviolet, x-rays and gamma-rays) totally ignore plasma. Keep in mind that making a sub-200 nm handheld laser is really really hard.}
The secret to avoiding the instant plasma armor problem is pulsing the beam.
Take one kilojoule's worth of laser energy and divide it up into 1,000 single-joule pulses separated by 5 microsecond intervals. Focus it down so the spot size is about one millimeter. The first pulse hits asteroid pirate epidermis. The pulse is fast enough and the energy is concentrated enough so that it creates a little explosion. This blasts a crater in the asteroid pirate's flesh up to four centimeters in diameter, depth of 2 centimeters.
Plasma and bits of flesh fly into the path of the beam but there is no beam there. The explosion was done by a single pulse, but the next pulse won't arrive for another 5 microseconds. The plasma vanishes almost instantly. 5 microseconds later roughly 90% of the flesh debris has cleared the beam path. Now laser pulse #2 arrives, sailing through a void with no plasma or flesh bits, and arrives at full strength causing a second explosion at the bottom of the crater. This creates a second crater. The two craters have a combined depth of 4 centimeters. Repeat for the remaining 998 pulses.
Dr. Schilling calculates you can bore a hole through soft body tissue about 30 centimeters deep before the tunnel collapses (taking about 0.005 seconds for all 1,000 pulses). Roughly the equivalent to a high-velocity pistol bullet or a small centerfire rifle.
The 5 microsecond pulse rate is optimized for soft body tissue, other rates are optimal for steel or other materials.

Sample Blaster Bolts
Bolt	Total Energy	Number of pulses	Pulse Energy	Intervals	Spot Size
Schilling	1 kJ	1,000	1 J	5 μs	1 mm
Campbell assault eq.	1 kJ	100	10 J	1 μs	10 mm
Campbell Light Laser Pistol	1.2 J	60	20 J	4 μs
Campbell Battle Laser	10 kJ	50	200 J	10 μs

Dr. Schilling
Whether you use lasers or particle beams, you'll need a bit over a kilojoule of output energy to reliably incapacitate a human target. In the case of a laser weapon, that energy would be subdivided into ~1 joule pulses at ~5 microsecond intervals, to achieve penetration in the face of a laser's natural tendency to deposit energy at the target's surface. Particle beams don't have that problem; boost the electrons up to a few hundred MeV, and you can dump the whole kilojoule's worth at once.

The plasma clears away easily in that time frame; debris is the real issue, and the driving force between the 5 microsecond pulse rate. That allows roughly 90% of the debris to clear the beam path, assuming a 1mm beam and instantaneous 1J pulses. 1 joule every 5 microseconds is optimal against soft tissue, other materials will want different pulse trains.

I'm assuming a weapon designed to penetrate ~30cm in soft body tissue. This gives about 15cm in bone or plastic, 5cm in brick or concrete, or 2.5cm in steel or most ceramics. Synthetics won't be very good at stopping energy weapons, even tough ones like kevlar, but you might be able to find a ceramic that could stop a laser beam with a centimeter's thickness or so. Particle beams are tougher to stop; it mostly comes down to sticking mass in the way without regard to material properties.

(ed note: if my slide rule is not lying to me, 1000 pulses at 5 microseconds per pulse will take 0.005 seconds. 1000 joules in 0.005 seconds is equivalent to 200 kilowatts)

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Luke Campbell
Keep in mind that in tissue, the cavity blasted out will collapse back on itself in a few milliseconds (and probably re-expand and collapse again in pulse-like oscillations for a few cycles).

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Dr. Schilling
Yes, and this is a problem if you want to push the penetration much above the 30cm I specified. If your pulses come fast enough to gouge out a meter-deep path before the surrounding tissue recoils back into the cavity and blocks the beam, they come too fast for the per-shot debris to clear the beam.
In soft materials, vapor expansion will carve out a hole much larger than the original one millimeter — I got four centimeters maximum hole diameter for soft body tissue, so the effect should be at least equal to a modern high-velocity pistol bullet, and perhaps comparable to a small centerfire rifle. Brittle materials are likely to shatter within a similar radius, tough stuff like steel will show little effect beyond the original hole.
And no, mirrors will not work as armor. The best finish you can reasonably expect to keep on an exterior surface, will still absorb 10-20% of the incident energy, which will be enough to burn through the outer layer on the first pulse. And the rough and now hot interior will be even less reflective.

I also mentioned earlier that lasers would likely have to have pulse energy and frequency tuned to the specific material being targeted. It might be possible to do this automatically, based on crude spectoanalysis of the material vaporized in each pulse, but if not expect penetration to be roughly halved if a laser weapon is fired at a target it has not been optimized for. Target-shooting lasers won't be optimized for flesh, and certainly not for ceramic armor, so there may be legal implications here. Particle beams are less likely to suffer such inconveniences.

Taking into account the inefficiency of the system, the input energy will likely be somewhere between two and five kilojoules per shot. So you could get fifty to a hundred shots from a pistol-sized non rechargeable energy source, or half that with a rechargeable battery. Automatic fire at anywhere up to 20 Hz (1200 rpm) shouldn't be a problem in the short term, though might cause cooling problems if you keep it up.
You also need to focus the energy on the target, with a spot size of a millimeter or less. With a laser, that gets kind of tricky. A 5-centimeter mirror, about the largest you can really imagine on a pistol, gives an effective range of perhaps sixty meters, beyond which the weapon starts losing penetration quite rapidly.

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Luke Campbell
If you are already talking about the laser excavating cavities several centimeters in diameter, sub-millimeter spot sizes do not seem necessary, you just need a moderate fraction of the cavity's maximum size.

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Dr. Schilling
No, you still need to get down to a millimeter or so to flash-boil water in a layer ~one optical depth in thickness. Once you do that, the steam will expand and spread the damage around, but if you don't hit the threshold for turning water into steam all you do is warm up the target.
And the mirror needs to adjust for target range - adaptive optics (flexible mirror with microactuators)coupled to a laser range finder seems to be the way to go here - you've already got the pulsed laser part of the rangefinder.

Conversation between Dr. Schilling and Dr. Campbell

Laser Bolt Structure

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  BattleLaser, artwork by Luke Campbell

Luke Campbell
{amount of damage caused by battle laser shot: 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart} I use my damage calculator here which lays out all of my physical assumptions and approximations, but which I think captures the basic physical processes of crater gouging. Since stress is concentrated at the tips of cracks, you may get individual cracks propagating beyond the distances listed below in brittle materials, but severe pulverization should be limited to approximately the distances given (as observed in impact and explosive craters).
Incident on meat, the aforementioned pulse train will blast out a hole 53 cm deep and 2.2 cm across (this is probably reported to one more significant figure than is justified). The diameter of the temporary cavity will be about 10 cm, but since muscle is highly elastic this will probably cause only bruising beyond the 2.2 cm permanent hole. Adding gristle and bone doesn't change this much - you get the same permanent cavity and depth in gristle, while bone will be drilled through to a depth of 29 cm, a permanent cavity diameter of 1.2 cm, and shattering and fracturing out to 1.45 cm diameter. Note that a typical person will be about 20 cm to 30 cm through the torso (depending on orientation), so this pulse would not only shoot through a person, but through the guy behind him as well.
Incident on plastic — in this case high density polyethylene — the pulse train will blast out a 32 cm deep and 1.3 cm across hole, with possible plastic flow out to 2.43 cm diameter.
Incident on sandstone, you get a 25 cm deep hole, 1.1 cm across, with shattering and cracking out to 2.1 cm. On granite, the hole is essentially the same except that shattering and fracturing is limited to 1.5 cm diameter. On concrete, the hole is again about the same depth and width, but now you can expect shattering out to about 3 cm.
Against structural steel, you get a 16 cm deep hole that is 0.65 cm across, and possible cracks or permanent deformation out to 1.1 cm. The very strongest maraging steels have the same size hole, but will lack any permanent deformations in the vicinity of the hole.
A representative titanium alloy might get an 18 cm deep hole 0.74 cm across, with possible permanent damage out to 0.84 cm diameter. Aluminum alloys will get drilled to 19 cm and 0.79 cm across, with possible permanent deformation out to 1.5 cm diameter.
High tech armor is likely to be some sort of carbon, perhaps diamondoid, fullerite, or nanotube weave. Against diamond I get a hole depth of 6.1 cm and a 0.26 cm hole diameter. Expect permanent damage out to 4 cm in the form of shattering and cracks. Against fullerite and nanotubes, the hole will be 7.7 cm deep and 0.32 cm in diameter, with possible permanent damage out to 0.41 cm.

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Anthony Jackson
(Luke Campbell: 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart)
Why that level of overkill? You should get the same penetration out of 100 pulses of 25J each, spaced 5 microseconds apart. You'll just have a hole that's half as wide, and you've just dramatically cut the energy requirements.

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  Holes of increasing aspect ratio. Note the build-up of ejecta around the entrance to the hole.

Luke Campbell
Two reasons, all relating to the fact that the hole is half as wide.
First, very large aspect ratio holes may be problematic to drill, based on issues of the ejecta interacting with the beam and the hole. With the pulse parameters I used, I'm looking at a 25:1 aspect ratio - which is probably doable although the hole will likely have constricted significantly near the end. At half the width, the aspect ratio will be more like 50:1, which is pretty extreme and may be unachievable. Also, if the hole is constricted, each subsequent pulse will produce a smaller bang, which will gouge out a smaller crater, which will in turn reduce the penetration from this optimistic assessment. In the limit of lots of small pulses, this should give a penetration that depends on the logarithm of the number of pulses, which quickly reaches a point of diminishing return.
Second, your range for maximum effect is cut in half, since you need to focus the pulses to within half the width to efficiently blast out the crater. Against diamondoid armor, the 200 J pulses require a 0.26 cm spot size for maximum effect and a 1 micron wavelength, 6 cm aperture laser will be able to be effective out to about 120 meters with a perfect Gaussian beam. If the craters are only half as wide, you would need to be twice as close.
Although now that I think about it, all my previous figures on the beam power were from the figures on power consumption, not beam power. Since I assumed by lasers were 50% efficient, all the previously stated beam powers are too large by a factor of 2 (and the details on the pulse trains which I retro-fitted to give the right beam power will be off as well). Ah well, I plead that I was distracted (I had just learned that I was going to be a daddy).

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Anthony Jackson
(Luke Campbell: First, very large aspect ratio holes may be problematic to drill...)
Hm. On reflection, this suggests that the ideal number of pulses in a blast may be fixed (probably somewhere in the 20-100 range), since the aspect ratio is basically about half of the number of pulses.
(Luke Campbell: In the limit of lots of small pulses, this should give a penetration that depends on the logarithm of the number of pulses...)
Pretty sure it's order 1/3, since the lost energy tends to go towards making the hole wider.
(Luke Campbell: Second, your range for maximum effect is cut in half, since you need to focus the pulses to within half the width to efficiently blast out the crater...)
On reflection, this may be problematic for unrelated reasons. Air breakdown in clean air occurs at upwards of 10¹⁰W/cm², but in dirty air it can drop down to 10⁸W/cm² or so. Your 0.26 cm spot size is 0.05 cm², so the dirty air limit is around 10⁷W or 10J/microsecond. For clean air, the 200J pulses are likely not a problem.

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Luke Campbell
(Anthony Jackson: Hm. On reflection, this suggests that the ideal number of pulses in a blast may be fixed, probably somewhere in the 20-100 range)
Yeah, that's the conclusion I've been coming to.
(Anthony Jackson: Pretty sure it's order 1/3, since the lost energy tends to go towards making the hole wider)
I can see this is true if you are mainly working via melting or evaporation of the material. If the pulses are blasting out a void, however, the energy deposited on the sides of the hole may not be sufficiently intense to deform the material. Of course, the hypersonic jet of ejecta may be able to strip material from the sides of the hole. So we are looking at penetration scaling at somewhere between the 1/3 power and logarithmically for large numbers of pulses. For small numbers of pulses we should, of course, be in a linear regime.
Looking at pictures of various aspect ratio laser drilled holes, the opening to the hole looks to have about the same radius regardless of aspect ratio, which is about the same as the width of the beam. As the aspect ratio of the hole increases, the hole constricts with depth, eventually becoming significantly narrower than the beam.
I am not sure if the same mechanisms that operate in close focus laser drilling necessarily take place in holes drilled as part of an attack by a laser weapon. For example, in laser machining the walls of the hole are often used as a waveguide to extend the depth of field of the laser beam. For weapons, this will be irrelevant at significant ranges. If loss due to multiple reflections down the waveguide is responsible for much of the constriction, then this will not be as much of an issue for laser weapons.
For pulse lasers, as long as you can get most of the energy of the pulse into a given area of the target material, you will blast out a full sized crater. So suppose the crater is 1 cm across (and thus you have a maximum spot size of 1 cm in which to focus your beam for maximum effect), and also suppose your beam is focused to 1 mm. You will continue to blast out full sized craters until ejecta deposition constricts some part of the hole to less than 1 mm. This will result in a much deeper hole than if your beam started out close to the threshold limit of 1 cm.
(Anthony Jackson: On reflection, this may be problematic for unrelated reasons. Air breakdown in clean air occurs at upwards of 10¹⁰W/cm², but in dirty air it can drop down to 10⁸W/cm² or so. Your 0.26 cm spot size is 0.05 cm², so the dirty air limit is around 10⁷W or 10J/microsecond. For clean air, the 200J pulses are likely not a problem.)
This is a very interesting observation. It may be that in air we can never be able to reliably penetrate carbon-armor materials.

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Anthony Jackson
Beam divergence for a near-IR laser (such as neodymium-doped yttrium aluminium garnet (Nd:YaG)) can be estimated as on the order of 1mm per (aperture in mm) meters, and focus tighter than 1-2mm is probably not useful due to issues of hole aspect ratio, so the range at which these weapons would retain full penetration is reasonable for their apparent roles (as assault rifle, SMG, pistol), though rather sharply capped as compared to conventional rifles (which, while not very effective beyond a few hundred meters, don't drop to irrelevance).

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Luke Campbell
I was envisioning these as pulsed lasers. With a pulse, so long as the light is delivered into a smaller spot than the crater which is excavated, the crater will explode to full effect. Since higher energy pulses explode to give bigger craters, higher energy beams will have longer range for the same primary aperture.
So take the battle laser, with a 6 cm aperture and 200 J pulses (fired in bursts of 50 pulses spaced a few microseconds apart). At 200 J, the crater blown out of a good structural steel is about 6.5 mm. So suppose we want the beam to focus into a 6 mm spot. If the beam wavelength is around 1 micron, we get a range of about 275 meters. As the materials get less strong, the crater gets bigger and the range of the laser gets longer — about 470 meters in concrete, or about 940 meters for meat. Stronger materials need you to be closer — for sooper carbon nano stuff, you will want to be closer than about 140 meters.

Luke Campbell

DIRTY LENS

(If you have droplets of water/ oil / mud on the lens and your first pulse hits it could the resulting steam eventually degrade the lens?)

An interesting question. For the parameters I assumed for these devices, a single shot is about 5 kJ in 0.5 milliseconds, or 10 MW of power time averaged over the pulse. At the lens it is spread out over a 6 cm diameter spot (since the lens is 6 cm in diameter). Since 100 J distributed over a 6 cm spot is not likely to give an impulsive shock wave, I'll treat this as if a 10 MW beam was incident on the lens debris.
I turn to the calculator and look at what 10 MW in 6 cm will do to granite — assume a piece of dust is equivalent to a tiny granite fleck. I find that the vapor pressure is 242 kPa — a bit less than two and a half atmospheres. This is much less than the structural strength of any reasonable lens material, so the evaporating dust fleck will not blast a hole in the lens (material strength of strong refractory materials are measured in tens of GPa or more — hundreds of thousands or millions of atmospheres). The temperature is 2584 K. This will burn unprotected diamond, so we will have to assume that the surface of the lens is not diamond. Zirconia has a melting point of 2986 K, so we can make a thin film covering out of that, with diamond underneath (diamond has excellent thermal conductivity and transparency). Silicon carbide is another possibility for a lens coating. In the half a millisecond of laser irradiation, the dust will evaporate to a depth of 0.06 mm.
So what looks like will happen to a bit of dust on the lens is that a thin layer of the dust will be heated to vapor. The vapor will expand, acting like a rocket to launch the dust off the lens. With a proper selection of materials, the lens will be undamaged.
Repeating the calculation with perfectly absorbing water (a model for mud), I find a pressure of about 6 atmospheres (615 kPa), a temperature of 433 K (a bit over boiling), and vaporization to a depth of 0.6 mm. This comes nowhere near harming the lens, and blasts the water off the lens with a puff of steam. In practice, the water is likely to be mostly transparent, and might boil throughout its volume or even transmit the beam without significant heating for very pure water rather than having a bottom layer evaporating.
Oops — SiC also burns when it gets too hot. It looks like zirconia will need to be the lens coating material.
Or rather than zirconia, cubic boron nitride could be used as a coating, since it is just about as hard as diamond, has extraordinary chemical stability, thermal conductivity, and thermal stability. Maybe you could make the entire lens out of cubic boron nitride rather than diamond.

Luke Campbell

HOW SOON

(ed note: in 2015 somebody asked Luke Campbell how far in the future such laser sidearms are.)

My best guess about the time span for pulsed lasers is maybe about thirty years, plus or minus fifty.
This would be for ship-board and vehicular weapons. Getting a laser into a rifle-sized package sounds like a much more challenging task.
Although over the last several decades laser power levels have been advancing faster than Moore's law, so who knows? Admittedly, that's for instantaneous power rather than time average power. And you would need to put a few kilojoules into a pulse train about a microsecond long, with individual pulses of tens of joules energy and nanoseconds duration. Modern pulse lasers that fit on a tabletop (as opposed to an ICF facility) are doing really good if they reach millijoules (1/1000^thof a joule) in a nanosecond, in a package much larger than a rifle, so they've got a long ways to go.)

Luke Campbell (2015)

LASER WOUND THRUST

(ed note: in 2017 somebody asked me if the ejecta from a laser wound would appreciably thrust or tumble a target who was in free fall. I asked Dr. Campbell. TL;DR: nope.)

 Luke Campbell
I'll work this out when I get a chance to go over my high energy laser absorption code. It should calculate the speed and mass of the ejecta as part of the intermediate calculations. I'll just have it print that out.
Incidentally, I find the lasers tend to work better with about 100 pulses than 1000.
The conceptual weapon fires over a one millisecond time period. That's roughly the period of oscillation of impulsive cavities in flesh (but a bit shorter, the cavities tend to collapse and oscillate with a period of several milliseconds), so a one millisecond beam could drill through a person without having the beam interrupted by the cavity produced by the violent vapor expansion collapsing back.
This one millisecond pulse is broken up into a number (about 100 or 1000) of individual "micropulses", each on the order of a nanosecond duration.

(Dr. Campbell returns from his calculations)

The easy one first. If you take a 1 MW beam and focus it to a 1 mm wide spot on a person for 1 millisecond, it is just about as effective at blasting out a hole on them as if you break the beam up into hundreds of nanosecond pulses (the armor penetration will not be as good, but still better than a bullet). My calculator tells us that the pressure of the laser-irradiated spot is 224 MPa. With a 1 mm diameter spot, this means the force is 176 Newtons. The beam lasts for 1 ms, but the hole it drills in meat is 71 cm deep — and most people are not that thick. Since you have constant drilling speed, and a typical cross section across the human body is 25 cm, you will be getting that force over about 1/3 of a millisecond. This gives an impulse of 0.06 N s. A 75 kg human would be sent moving at the blistering speed of 0.08 mm/s (about 2 minutes to move one centimeter). If you shot someone at a distance of 1 meter from their center of mass and were drilling the hole more-or-less perpendicular to the vector from their center of mass to the point of incidence, and assuming we can calculate the moment of inertia as if the person were a uniform rigid rod 1.6 meters long (for I = 16 kg m²), the target would be set rotating at a speed of about 0.004 radians per second (or about 1500 seconds for a full revolution). (so it would take 25 minutes for a full revolution. This is about twice as fast as the minute-hand on an analog clock for those of you old enough to have seen a non-digital clock)
Now consider breaking that 1 MW, 1 ms pulse up into 100 pulses of 1 ns duration and 10 J each, separated by 10 microseconds (for the same total pulse duration and beam energy). The pressure in the irradiated spot is 228 GPa so the force is 180 kN. Over 1 ns, that's an impulse of about 1.8×10^-4 N s. It will take about 20 of these pulses to blast through your target, so the total momentum transferred is 0.0036 N s. So you would get roughly 1/15th the impulse, 1/15th the change in speed (0.005 mm/s, 33 minutes to move 1 cm), and 1/15th the rotation (2.7×10^-4 radians per second, 22,500 seconds or 6.25 hours for a full revolution) as from a single pulse.
I suspect that the splatter of blood and guts will deliver significantly more momentum to your poor target than the evaporate, but that's well beyond the level of simple calculations.

---

Luke Miller
As you drill deeper, would you have less evaporate as more energy is transfered into surrounding tissues?

---

Luke Campbell
To some extent. Laser drilled holes tend to be limited to aspect ratios of 1:20 to 1:30 or less. In metal, the surface of the drill-hole tapers inward. This intercepts more and more of the beam. The losses are not as bad as it might seem at first, because the sides are still somewhat reflective and form a wave guide that funnels the beam to the end of the hole. Still, too deep of a hole can interfere with drilling even deeper.
In meat, it is not quite as clear what's going on. For obvious reasons, this is not something people nowadays have a lot of experience with. You have the evaporation of the meat producing a high vapor pressure, which expands out the surrounding meat to produce a big hole or cavity. The laser beam is much narrower than the cavity, so it might be able to just sail through and hit the back wall, producing even more high pressure vapor to dig out and deepen the cavity. Experiments might reveal complications to this model — if anyone wants to fund me to buy a megawatt laser and drill holes in slabs of meat, I'm listening.

Luke Campbell (2017)

Ray Beams

Ray beams are lasers that emit needle-thin beams that produce a white-hot plasma along their path and easily burn deep holes into their targets. The main difference between ray beams and blasters/heat-rays is that ray beams use vacuum frequencies. These are frequencies shorter than 200 nanometers: extreme-ultraviolet, x-rays, or gamma-rays. Note that another name for frequencies shorter than 10 nanometers is "nuclear radiation."
Blasters and heat-rays use non-vacuum frequencies, such as visible light or infrared. These frequencies freely pass through Terra's atmosphere, but have to burn through plasma. Vacuum frequencies are the opposite: they have to burn through atmosphere, but they sail through plasma with nary a problem. Which means vacuum frequencies do not need to resort to the blaster trick of pulsing the beam. But a vacuum frequency laser beam has to burn through all the atmosphere between the laser muzzle and the target before any of the (remaining) laser energy can start inflicting damage.
The main problem it is astonishingly challenging to make a laser that uses vacuum frequencies.
Extreme Ultraviolet is incredibly difficult to work with. It pretty much tries to destroy any matter it hits. That's why they call them "vacuum frequencies", they work best in vacuum. This means you cannot use lenses to focus the beam. You cannot use windows to isolate the lasing element from the environment. Ordinary mirrors do not work (the UV burns holes in it), you have to use grazing incidence mirrors with special dielectric coating. And even then you are lucky to get 70% reflection efficiency.
Soft x-rays have all the above problems but worse. The mirrors have to be smooth down to 1/3 of a wavelength, which with soft x-rays means no mirror imperfections larger than 10 atoms high. And now you have a pumping problem.
You see, the laser generator has to be "pumped" with large amounts of the same frequency it will emit. This is not a problem with infrared, visible light, or ultraviolet. But there are not any good sources of large amounts of x-rays or gamma rays. At least short of a nuclear explosion, that is. The current best solution is free-electron lasers. However free-electron lasers have abysmal maximum efficiencies, and are generally hundreds of meters long.
Hard x-rays have wavelengths smaller than an atom, so mirrors will not work. All matter is rough on this scale. The proposed solution is to use x-ray crystal diffraction to make a difractive resonant cavity. Note that hard x-rays are ionizing radiation, so you are now inside the realm of nuclear radiation lasers.
Gamma-rays would make the most penetrating ray beams of all. Unfortunately there is no known way to focus gamma rays, which is a problem if you are trying to make a laser. And like hard x-rays there is a problem pumping the blasted thing. The only known way of making a gamma-ray laser is with an "Excalibur" style bomb-pumped laser. Which is problematic as a handgun.

Power Supply

• 

  Buck Rogers in the 25th Century (1938) Artwork by Dick Chalkins

• 

  Laptop after battery fire.

The crummy efficiency of lasers make it clear that the laser's battery will be carrying plenty of juice. Anything carrying that much energy will be at least slightly unstable. In other words, it wouldn't take much to make a charged battery into a home-made bomb (which might come in handy if one suddenly needed a bomb.). You might have read news reports about laptop computers whose batteries suddenly burst into flame.
And don't even think about sticking a fork into the open contacts.

This has been observed somewhat tongue-in-cheek by John Routledge as Routledge's Law:

Routledge's Law

Any interesting battery material for a laser gun would be more usefully deployed as an explosive warhead.

John Routledge

He also notes the problem with ammunition cook off. If you are holding a fully-charged laser pistol, and some lucky enemy sniper manages to score a direct hit on the pistol's battery, it is going to be just too bad if the resulting explosion vaporizes you and all your friends within a large radius.
Assuming a worst case of 5 kilojoules per shot and a rechargeable magazine containing 50 shots, the magazine is packing 250 kilojoules. This is the equivalent of 250,000 * 2.7778×10^-4 = 70 watt-hours or 250,000 / 4,500 = 55 grams of TNT (For comparison purposes, a standard 8 inch stick of dynamite is about 208 grams and hand grenades used by the US Army have explosive charges of 56 to 226 grams of TNT). At his specified energy density of 2.5 kilojoules per cubic centimeter, this would imply a magazine volume of 100 cm³. this is approximately the same volume as forty-two .45 caliber rounds.
You may remember that in Star Trek, phaser hand weapons could be set to explode like hand grenades, a "forced chamber explosion."
The above is a reasonble energy magazine. At the ludicrous end, in L. Neil Smith's BRIGHTSUIT MACBEAR, we find the five-megawatt fusion-powered pistol.

I make a point of noting — although mine are superconducting batteries — that the distinction between "battery" and "grenade" is essentially disabling the safety circuits that stop it from discharging Much Too Fast and causing a sudden, catastrophic, energy-dumping quench. But nevertheless, energy storage with that sort of energy density is just too useful not to use — so a lot of work has gone into very good, no-fail safety circuits.
(In ISS agent and special forces training, of course, they teach you how do to exactly this: Explosive Overclocking)
That said, they don't worry about it much for military applications, either, because you have to be a very good, very cocky sniper with an amazingly good gun to successfully hit a target that small in just the right way to break through the deliberately-hardened-against-this-scenario shell and fracture the loops.

Alistair Young (2016)

Power Parameters

• 

 There are several ways to measure the power source of a laser weapon with respect to how big and how heavy it is. This is useful to know, because it helps you figure out how many shots the gun has in it. Unfortunately the units are confusing, and some times the same name is used for two different terms. And I am probably going to do a poor job of explaining. When you give up on me, skip to the next section.

ENERGY

This is the total amount of electricity or whatever in something (e.g., a battery or a laser bolt).
Energy is measured in Joules (J, refer to the Boom Table).
It is a property that must be transferred to an object in order to perform "work", which in this case means "blasting a flaming hole into your opponent."

POWER

This is how fast you can extract energy from your battery or whatever. Or insert energy: you may have noticed that it irritatingly takes a few hours to charge up your smartphone battery, instead of charging up to full in a fraction of a section as we wish they would.
Power is measured in Joules Per Second (J/s), also known as Watts.
Remember how energy must be transferred to an object in order to perform work? Power measures how fast the energy is transferred, or "how many seconds does it take to drill a blazing laser hole in your opponent."

POWER-TO-WEIGHT RATIO

This is how much power is crammed into a gram of something, usually a battery. Each type of battery or other power source has a power-to-weight ratio rating. Given the ratio and the power requirement, you can calculate the weight of the power source. Conversely given the ratio and the maximum weight requirement, you can calculate the power contained.
Power-to-weight ratio is measured in Watts Per Kilogram (W/kg).
This is also called "specific power" or "power-to-mass ratio".

WEIGHT-TO-POWER RATIO

This is the inverse of Power-to-weight ratio, and is generally only used with vehicles. Not batteries. It is measured in Kilograms Per Watt. It is also called "power loading".

ENERGY-TO-WEIGHT RATIO

This is how much energy is crammed into a gram of something, usually a battery. If the power contained remains the same but the energy-to-weight ratio rises, the battery becomes lighter.
Each type of battery or other power source has a energy-to-weight ratio rating. Given the ratio and the energy requirement, you can calculate the weight of the power source. Conversely given the ratio and the maximum weight requirement, you can calculate the energy contained.
Energy-to-weight ratio is measured in Joules Per Kilogram (J/kg). Occasionally you'll see it measured in Watt-Hours Per Kilogram (Wh/kg), where 1 watt-hour equals 3600 joules. Of course 1 watt-second equals 1 joule.
This is also called "specific energy" or "energy-to-mass ratio".

ENERGY DENSITY

This is how much energy is crammed into a volume of space of something, usually a battery. If the power contained remains the same but the energy density rises, the battery becomes smaller.
Each type of battery or other power source has a energy density rating. Given the ratio and the energy requirement, you can calculate the volume of the power source. Conversely given the ratio and the maximum volume requirement, you can calculate the energy contained.
Energy density is measured in Joules Per Cubic Meter (J/m³).
For purposes of comparision a conventional .45 caliber cartridge for a slugthrower has a volume of approximately 2.4×10^-6 cubic meters. If the volume of a battery capable of powering one laser bolt is larger, the slugthrower is more efficient.
Yes, the term "energy density" was used in the section on heat rays with respect to how many joules per square centimeter of skin area was inflicted. This is the wrong term to use, but I am unsure what the right one is.

---

PWR = WPR / DT
where:
PWR = power-to-weight ratio of power source (W/kg)
WPR = energy-to-weight ratio of power source (J/kg)
DT = time to totally discharge all the energy (sec)

BM = (LE * LPS) / PWR
where:
PWR = power-to-weight ratio of power source (W/kg)
LE = energy in one laser bolt (J)
LPS = laser bolts per second
BM = battery mass (kg)

---

Note that batteries generally have pretty good energy density and energy-to-weight ratios, but lousy power-to-weight ratios. They contain lots of energy, but it trickles out real slow.
Capacitors are the opposite, with lousy energy density and energy-to-weight ratios, but pretty good power-to-weight ratio. They do not contain lots of energy, but what they have can be spat out in a fraction of a second.
To try and get the best of both worlds, they engineer things so large batteries are feeding a capacitor, and the capacitor feeds the laser or whatever. You've probably seen this in a camera strobe. It flashes, then you have to wait for the "charged" light to come on before the strobe will flash again. The capacitor makes the strobe flash, then the delay comes from the battery slowly recharging the capacitor.

Power Sources

• 

  Laser Pistol, Lost In Space (1965)

• 

  Laser Pistol, Lost In Space (1965). Official replica, autographed by Jonathan Harris.

• 

• 

  Grenade Gun, Hamilton Invaders by Remco Toys (1964). This was the toy that the Lost In Space prop designers used to created the Laser Pistol.

• 

  I have no idea how Michelle Angelo got her hands on a grenade gun.

 Dr. Schilling assumes that in the near future rechargable batteries will reach an energy density of 2.5 kilojoules per cubic centimeter (2.5×10⁹ J/m³). James Borham says that currently available lithium-polymer rechargable batteries have an energy density of 1.08 kilojoules per cubic centimeter (1.08×10⁹ J/m³).
Anthony Jackson says ultracapacitors may reach energy-to-weight ratios of 100 J/g (1×10⁵ J/kg).
Asphalt-lithium batteries may charge 20 times faster than conventional lithium ion batteries:

• Energy-to-weight ratio: 3.4×10⁶ J/kg
• Energy Density: ~8.5×10⁹ J/m³
• Power-to weight ratio: 1,322 W/kg

Example

Asphalt helps lithium batteries charge faster
Winchell Chung
Are they near 2.5 kilojoules per cubic centimeter? The article says 943 watt-hours per kilogram, but I am not sure what the density of the battery material is.
Luke Campbell
Winchell Chung, with the given information, the specific energy is about 3.4 kJ/g. Li-ion batteries are about 2.5 g/cm^3. Assuming this new electrode doesn't significantly change the density, we get something like 8.5 kJ/cm^3.
Winchell Chung
     Luke Campbell, thanks!
     I had calculated that a .45 caliber cartridge is about 11.43 mm x 23 mm, which gives it a volume of about 2.4 cubic centimeters.
     At a rechargeable 2.5 kj/cm^3 this means a battery the size of a .45 round would hold a good 6 kilojoules, enough for an extra-strength laser bolt.
     So this new stuff allows a laser firearm to have a better ammo density than a slugthrower weapon.
Luke Campbell
Winchell Chung, but note that with the listed specific power of 1.322 kW/kg, to get your 6 kJ laser to shoot even one time per second you will need a 4.5 kg battery. So either we need further improvements in specific power, or use the battery to charge up a supercapacitor that will allow, say, 10 rapid-fire shots and that can be continually recharged at a slower rate by the battery.

---

BM = (LE * LPS) / PWR
where:
PWR = power-to-weight ratio of power source (W/kg)
LE = energy in one laser bolt (J)
LPS = laser bolts per second
BM = battery mass (kg)


BM = (LE * LPS) / PWR
BM = (6,000 * 1.0) / 1,322
BM = 6,000 / 1,322
BM = 4.5 kg

You'll also need a power source. Three approaches come to mind, two of which are pretty sure things. Burning a liquid propellant in a pulsed MHD generator or flux compression generator can be done now, and there are thermal primary (i.e. non rechargeable) batteries that are pretty close to what would be needed. Unfortunately, both of these involve high operating temperatures and expendable power sources.
Advanced bipolar designs of conventional secondary batteries might be up to the task, and have the advantage of being fully rechargeable. Besides, it is rather humorous to consider that a 21st-century laser weapon might really be powered by a lead-acid or NiCad battery.
I'll assume non-rechargeable systems at an energy density of 2.5 kilojoules per cubic centimeter, which is quite plausible. You might consider a rechargeable battery pack as an option, with half the capacity of the non-rechargeables.

Dr. Schilling

It turns out that the future is already here. Lithium-polymer cells are rechargeable, and have an energy density of 1.08 kJ/cm³. This is just shy of half of Dr. Schilling's assumed energy density.
As for nonrechargable batteries, check out the various molten salt batteries. They're stored as a solid, so they can be stored 'charged' virtually forever. As soon as you bring them up to operating temperature (400 C or more), and as long as you keep them there, you have an incredibly high output battery. The military has used them like this for a very long time, and most current research is focused on making them rechargeable. I can't find any hard numbers on them (apparently the energy density varies widely), but it's clear that they can have very high energy density.

(Ed. Note: for a list of energy densities of various storage devices, refer to the Wikipedia article)

James Borham

Either way, the energy will have to be stored in and dumped from a capacitor or (if the switching problem is solved) inductor to meet the peak power requirement. Electrochemical double-layer capacitors ought to do the job if nothing else is available.

(Ed. Note: using a capacitor will make the laser operate in a similar manner to a camera strobe. You fire, then you have to wait for the little "charged" light to come on before you can fire the next shot.)

Dr. Schilling

If you can combine a chemically fueled laser with the type of pulse behavior needed for optimal armor penetration (a rather formidable challenge), a 'laser rifle' might not be too bad; under ideal circumstances a 10 kilojoule laser might be similar in lethality to a rifle, and could even have fuel requirements on a par with the ammunition weight of a rifle. Of course, this requires a very narrow focus beam (a couple millimeters wide) and you'll be limited to optical or near-IR. If we assume a helium-neon laser (634 nm) a 10 cm mirror would have a beam divergence of 15 microradians, giving a useful range of 100 meters or so (3mm spot).
So...this requires massive tech inventions and an expensive, probably delicate weapon to reach the performance of a rifle. This is not exactly worthwhile.
Efficient ultracapacitors might allow around 100J/g, which in combination with an excimiter laser (and probably a fuel cell for recharge) might be enough for a decent sniper weapon and could give a quite large number of shots on a fuel tank, though the number of shots at one time would be quite limited.
On the severe handwavium side, there's gamma-ray lasers powered by nuclei in metastable states. In this case, the energy density is immense (1.2 GJ/g for Hf-178m2, for example) and diffraction limits are unlikely to be relevant (a 1mm diffraction-limited lens could project a constant 1mm beam for 1,000 km or so). However, the technical problems are, to say the least, formidable, and even if resolved, the 'fuel' is highly radioactive; simply avoiding killing the user would require large amounts of shielding.

(ed note: the handwavium Hf-178m2 is the basis for the infamous Hafnium bomb. Yes, it exists. Yes, it stores incredible amounts of energy in a very tiny package. No, we have not yet figured out how to increase the power output to better than half of the energy discharged every 31 years.)

Anthony Jackson

(ed note: Noted science fiction author Charles Stross has this deliciously biting analysis of a ridiculous proposed laser weapon called the Stavatti TIS-1 Gasdynamic Laser Infantry Rifle)

---

The laser itself looks pretty reasonable, in an if-we're-talking-about-laser-weapons way ("laser" and "weapon" belonging in the same sentence in the same way as "automobile" and "rubber-band powered"), but the power supply is what makes this one special. In search of the ultimate in infantry-portable enemy-slaying goodness, Stavatti have one-upped all previous attempts by proposing to use a radioisotope generator containing 750 grams of Polonium-210. This would, of course, provide the necessary 100 kilowatts to power the man-portable death ray. It would also provide 125 petaBecquerels of radiation (as compared with the 100 pB of Cesium-137 spewed out by the B reactor at Chernobyl), and the need to pressurize it to 4000psi leads me to agree with my military informant's summary that "it might actually achieve the near-impossible feat of making Project PLUTO look environmentally benign by comparison."
I will also confess that my suspension of disbelief took a slight knock when I got to the bit about the TIS-1 also sporting a bayonet lug.
Anyway, I'd just like to say that I fervently hope the Pentagon's planning and procurement folks give this proposal the attention it undoubtedly deserves. As Polonium-210 is accounted for (when you can buy it) at a market price of roughly $12 million per gram, this weapon system will cost roughly $54Bn per rifle per year to run — the US Army could afford almost an entire squad, and thus might have to scale back their other projects accordingly.
(PS: 100 kilowatts is, in automobile terms, about 130 horsepower. So if you were to ditch the Dr Strangelove power supply the gadget could plausibly be mounted on a HMMV or Land Rover. But I find that idea somewhat disappointing ... and anyway, what would be the point of sticking a bayonet on a vehicle-mounted laser cannon?)

blog post by Charles Stross

There was discussion about ultracapacitors:

Apparently ultracapacitors are approaching 50% of the energy capacity of a lithium ion battery. Boost that over 100% and it would make a nifty power source for a man-portable laser weapon.

Winchell Chung

It looks to me like they expect 25% to 50% of the energy of a Li-ion battery. They still haven't made a prototype yet. It is exciting work, and I hope they succeed.

Luke Campbell

Hm. 50% would be 80 Wh/kg (288 kJ/kg). This is approximately 7% of the energy density of a typical chemical propellant and 0.6% of the energy density of gasoline. Incidentally, EEstor is claiming 1330 Wh/kg, but I'm not convinced that I believe them.
Note that thin film lithium and lithium-ion batteries have already pushed significantly beyond the capacity of lithium-ion. For current (if non-commercial) versions, I'm seeing numbers of around 250 Wh/kg and 2500W/kg, which is a bit low power density for a shot from an energy weapon. Theoretical potential is substantially higher.
For amusement: 2nd generation batteries in Ken Burnside's Attack Vector: Tactical game hold 2 gigajoules in a 25 ton structure, which works out to 80 kJ/kg or 22 Wh/kg, and can discharge in 16 seconds (or possibly less), which works out to 5 kW/kg. However, I'm pretty sure that a 1 hullspace component that can provide 1 energy point per game-turn segment for 20 segments (thin-film Li-ion with no tech improvements other than scaling and commercialization) would be gamebreaking. For that matter, 7th gen batteries (extrapolating from high end ultracapacitors) would rather distort the game as well.

Anthony Jackson

The thin film stuff should suffice for electrically powered projectile weapons, if you carried a backpack of batteries. If you figure a modern assault rifle packs something like a 1.5 kJ punch, and if you can get ~50% electrical ⇒ mechanical efficiency, and you want to be able to autofire at 10 round/s, you'll draw 30 kW. This is about a 15 kg pack for modern lithium batteries, 12 kg for your thin film varieties.
On the other hand, you could fire off many hundreds of shots if you had enough bullets. If you limit your fire to 3-round bursts, you could cut the power draw perhaps in half (depending on how fast our soldiers pull the trigger), and thus will only have to schlep around half as much weight. Needless to say, the batteries will be used to charge up a capacitor for the intermittent high power pulse used to launch the projectile.
Near future heat-ray style lasers are expected to be practical weapons at about 100 kW. This would require a 40 kg pack using the thin film batteries, but would give you 6 minutes of continuous lasing. Note that 100 kW is for use against rockets and thin skinned aircraft, it might or might not be useful against humans!
If, as I suspect, pulsed lasers are more efficient at causing death and destruction, you could get by with smaller power packs.
In my pet future setting, admittedly optimistic "battle lasers" put out lethal 5 kJ beams at full power, and draw 10 kJ. They can sustain 2 shots/second if you want to avoid heat buildup, but can be fired more rapidly for short periods if they have the electrical power available.
Lower power beams allow significantly higher rates of fire, although they are not too good against foes with armor. Something like could use an 8 kg pack for 2 full power shots/second if using the thin film lithium batteries, and would give you 720 shots. Combine this with something like a 1 kg ultracapcitor for rapid fire of a limited number of shots when you need them. The ultracapcitor recharges from the battery pack when you are hiding behind cover, switching between targets, crawling through the mud, or whatever else you are doing to avoid being shot.
(For what its worth, my setting uses "fast discharge power packs," roughly modeled on ultracapacitors, with specific energies of 200 kJ/kg and specific powers of 40 kW/kg. There are also "high capacity power packs" with three times the specific energy but one third the specific power if you want to tote around a heavy pack that gives you lots of shots, as well as various batteries that give even higher specific energies but even lower specific powers.)

Luke Campbell

Luke Campbell
Here's some artwork of mine on this issue

• 

  Artwork by Luke Campbell

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Isaac Kuo
That looks awesome! One minor idea—I notice that the layout is similar to a modern automatic rifle with the "barrel" lined up with the butt stock. This makes sense for modern automatic weapons because it minimizes muzzle rise due to recoil. Of course, a laser weapon has no inherent recoil.
Having the butt stock below the line of fire allows someone firing from a prone position from behind cover to have a lower profile. That's why single shot rifles had a downward sloping stock.
Similarly, having a large box magazine stuck to the bottom of a weapon forces the user to have a higher profile in a prone position. This is why some guns had magazines off to the side, despite the balance issues and the annoying carrying ergonomics.

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Luke Campbell

Having the butt stock below the line of fire allows someone firing from a prone position from behind cover to have a lower profile. That's why single shot rifles had a downward sloping stock.

That's a good idea. I'll keep it in mind for my next model.

Similarly, having a large box magazine stuck to the bottom of a weapon forces the user to have a higher profile in a prone position. This is why some guns had magazines off to the side, despite the balance issues and the annoying carrying ergonomics.

This makes me wonder where to put it. I suppose you could put it on the side, since a battery or ultracapacitor doesn't actually have to stick out like a cartridge feeding magazine. Putting the power pack forward of the grip seems like it would make it easier to switch an exhausted pack for a fresh one, probably on the side of the off hand. On the other hand, if you have a power cable from a larger battery or capacitor pack worn on the belt or as a backpack, a connection near the butt end would seem to present fewer problems with the cable snagging on things.

---

Christopher Thrash

This makes me wonder where to put it.

Put it on top of the frame in back, behind the optics and above the buttstock. Make it as long as possible while still able to fit into a vest pouch, and flat enough to not obscure the sighting mechanism. Think of a handier version of the G11 magazine, mounting in back rather than in front.

• 

  G11 with magazine

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Isaac Kuo

This makes me wonder where to put it.

I'm sorry, I actually don't think your energy pack sticks out very far. I was thinking of the problems with normal rifle/submachinegun box magazines. Box magazines full of rifle/pistol rounds are long and thin due to the way the feed mechanism works. Besides the double stack of rounds, there's a need for a rather bulky magazine follower for reliable feeding.
Your energy pack doesn't need to have such a shape, so it doesn't need to stick out so much. The amount your design sticks out is not a problem. You could lower the profile a little by placing the energy packs to the sides of the fore-end, but this is of dubious benefit.
Speaking of which, having two energy packs means that you can reload while always having some "rounds in the chamber". Instead of having a vulnerable period when you have no firepower, you always have one energy pack available.
The energy pack could be the butt stock itself.

Business end of a laser pistol? from sfconsim-l (2007)

• 

  Laser Rifle, Lost In Space (1965)

• 

  Laser Rifle, Lost In Space (1965)

Modular Power

• 

  Phaser 1 snaps into pistol grip power pack to become a Phaser 2

• 

  Phaser 1 is carried in the small of the back

 In science fiction an uncommon power supply is a modular supply. This is where you can add a variable number of power supply units to your weapon as if they were a stack of Lego bricks.
Ian Borchardt says the proper term for this capability is "upgradable". My personal favorite term is "stacked". (In some role-playing games a player's die rolls or characteristics are subject to modifiers, for example a magic sword that adds +5 to the player's strength or doubles endurance. If several modifers can be applied one after another, the terminology is that the modifiers can "stack." If you've never played an RPG then the preceeding sentences were total gibberish.)
The example of a modular power weapon that comes to mind is the good old Phaser from Star Trek.
A type 1 phaser is unit about the size of a bar of soap, and functions like derringer-sized directed energy weapon. A low-powered low-ammo discreet easily-concealable weapon. The Trek writers bible says a type 1 is something the crew would carry on a diplomatic mission to a friendly planet, where you didn't want to be obnoxiously packing heat but not totally defenseless either. Something that a stereotypical woman from a 1950s pulp detective story would tuck into their garter belt, handwarming muff, or purse. In Star Trek the type 1 phaser would be carried in the small of the back near the kidney concealed under the shirt, clinging to the pants by virtue of the "magnatomic adhesion area" (high-tech velcro). Type 1 phasers are worn right next to the communicator.
Snap the type 1 phaser into the larger power pack and it becomes a type 2, a phaser pistol. A handgun-sized directed energy weapon. Something a policeman or a military officer would carry as a service pistol. Or the equivalent of a frontier cowboy's six-shooter.
The Star Trek original series did not take it to the next logical step. Instead it made an outlandish phaser rifle that had no kindred spirit with the phaser pistol, and which was used for only one episode. A pity.
However, in the cancelled Star Trek II project they would do the logical thing and have the type 2 phaser pistol snap into a shoulder stock with a larger power pack to make a type 3, a phaser rifle. A long-gun-size directed energy weapon. Something a military soldier would carry.
The stacking phaser is a limited case of the "modular weapon" concept.

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  In the TV secret-agent show The Man from U.N.C.L.E. the agents were issued a service weapon based on a Walther P38 9mm Parabellum. By stacking the pistol with modules, it could be converted into a carbine/sniper rifle.

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  The real-world Beretta U22 Neos pistol can be stacked into a carbine with the addition of a carbine kit. Since a carbine is a weapon with a long barrel which shoots pistol sized ammo.

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  Phaser 1 inserted into pistol grip power pack to make Phaser 2
  from Star Trek: Discovery

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  Turn release knob to remove Phaser 1 from pistol grip

STAR TREK II

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  Phaser from Star Trek Phase II (1978). Image from Forgotten Trek

PHASER I: features fully self contained, operable components with a touch actuated lighted settings bar and side-mounted trigger. Batteries included (re-chargeable). Nose key lights function with trigger for easy optical matting of phaser beam. Features different color for each energy setting, plus on/off button for total shutdown.
Energy indicator bar colors: (front to back) Green: stun (neural effect), Red: kill (neural effect), Yellow: heat (molecular movement), Blue/White: disintegrate (molecular disruption)
Special feature: overload. simultaneous depression of all four settings buttons will arm the phaser for explosive overload (grenade effect). All four color bars flash warning until canceled with off button.

(ed note: the prop designers also added a row of beam emitters, so the weapon could be fired as a fan beam)

PHASER II: features easy interlocking with phaser one. Nose key lights now function with hand trigger. Features top inserted dilithium crystal power booster (pulsating light). Perfectly balanced, phaser two will stand up on any flat surface without support. Features overall cool silver/blue coloration. Exact size of Colt .45.
PHASER III: features easy interlocking with phaser two. Grip and operation remain the same. Connects to handle and undercarriage — drape-fit over forearm. Arm features booster packs (lighted). Overall shape reminiscent of old-style rifle stock.

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  In this design, the phaser 1 fires from one side when alone, but the opposite side when inserted into the handgrip to make a phaser 2. This seems to me no less than a deadly malfunction just waiting to happen.
  from Weapons and Field Equipment 2. Drawn by Shane Johnson for the Noron Group

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  The phaser 5 adds two arrays on each side so it could fire an extreme fan beam.
  from Weapons and Field Equipment 3. Drawn by Shane Johnson for the Noron Group

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  Concept art for phasers to be used in Star Trek: The Next Generation. None of these concepts were actually used.
  artwork by Rick Sternbach

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  The man known as Captain Robt T. April designed this interesting take on a phaser rifle. He based it on hints from Matt Jefferies original design sketch. Mr. April showed this to Bjo Trimble and Mike Okuda, and both said that this is probably spot-on to what Jefferies would've cooked up.

External Power

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  Traveller laser carbine, with back-pack power supply. Artwork by William Keith (1980)

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  Traveller laser pistol, with belt power supply. Artwork by William Keith (1979)

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  Traveller laser pistol, with belt power supply. Artwork by William Keith (1981)

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  Deflagrating gun, Barbarella by Jean-Claude Forest (1964).

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  Note the weapon's power pack strapped to the leg. "Deflagration" means "cause to burn with great heat and intense light". In other words it lies somewhere between "burns quietly" and "explodes"

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Before laser bullets are developed, you might find laser pistols with separate power sources. A large battery strapped somewhere on your body, connected to the laser pistol or rifle with a power cable.
In the role playing game Traveller, laser carbines are powered by a large battery worn in a back pack. In the Barbarella comic, deflagrating guns have their battery strapped to the upper leg. In William Tedford's Silent Galaxy AKA Battlefields of Silence, the hand laser's battery pack is strapped around the wrist.
Gene Roddenberry's original conception of the Star Trek phasers had a connection between the guns and the "power belt." He visualized the belt looking something like a waist-type life preserver, having individual power units, three inches by six inches. The units can be replaced, just as bullets in a gun can be replaced
There was an amusing scene in a remarkably bad '50s movie called Teenagers from Outer Space. The hero unfortunately broke the power pack on his focused disintegrator ray. He manages to cobble together a solution just in time to save the day. He attaches a cable from a nearby high-tension power line, and convinces the power plant to shove the generator output up to maximum!

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  Focused Disintegrator Ray from Teenagers from Outer Space(1959).

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  Atomic Disintegrator toy by the Hubley Manufacturing Co. (early 1950's).

GALACTIC PATROL

“Whichever way we look there are too many ‘ifs’ and ‘buts’ to suit me,” Kinnison summed up the situation finally. “If we can find them, and if we can get up close to them without losing our minds to them, we could clean them out if we had some power in our accumulators (fancy word for "battery"). So I’d say the first thing for us to do is to get our batteries charged. We saw some cities from the air, and cities always have power. Lead us to power, Worsel—almost any kind of power—and we’ll soon have it in our guns.”

---

“No danger of that,” replied the Velantian. “There are no windows in any of these rooms, no light can be seen from outside. This is the control room of the city’s power plant. If you can convert any of this power to your uses, help yourselves to it. In this building is also a Delgonian arsenal. Whether or not anything in it can be of service to you is of course for you to say. I am now at your disposal.”
Kinnison had been studying the panels and instruments. Now he and vanBuskirk tore open their armor—they had already learned that the atmosphere of Delgon, while not as wholesome for them as that in their suits, would for a time at least support human life—and wrought diligently with pliers, screwdrivers, and other tools of the electrician. Soon their exhausted batteries were upon the floor beneath the instrument panel, absorbing greedily the electrical fluid from the bus-bars of the Delgonians.
“Now, while they’re getting filled up, let’s see what these people use for guns. Lead on, Worsel!”
With Worsel in the lead, the three interlopers hastened along a corridor, past branching and intersecting hallways, to a distant wing of the structure. There, it was evident, manufacturing of weapons was carried on, but a quick study of the queer-looking devices and mechanisms upon the benches and inside the storage racks lining the walls convinced Kinnison that the room could yield them nothing of permanent benefit. There were high-powered beam-projectors, it was true, but they were so heavy that they were not even semi-portable. There were also hand weapons of various peculiar patterns, but without exception they were ridiculously inferior to the DeLameters of the Patrol in every respect of power, range, controllability, and storage capacity. Nevertheless, after testing them out sufficiently to make certain of the above findings, he selected an armful of the most powerful models and turned to his companions.
“Let’s go back to the power room,” he urged. “I’m nervous as a cat. I feel stark naked without my batteries, and if anyone should happen to drop in there and do away with them, we’d be sunk without a trace.”
Loaded down with Delgonian weapons they hurried back the way they had come. Much to Kinnison’s relief he found that his forebodings had been groundless, the batteries were still there, still absorbing myriawatt-hour after myriawatt-hour ("myria" is an obsolete metric term for 10⁴ or ten-thousand) from the Delgonian generators. Staring fixedly at the innocuous-looking containers, he frowned in thought.
“Better we insulate those leads a little heavier and put the cans back in our armor,” he suggested finally. “They’ll charge just as well in place, and it doesn’t stand to reason that this drain of power can go on for the rest of the night without somebody noticing it. And when that happens those Overlords are bound to take plenty of steps—none of which we have any idea what are going to be.”
“You must have power enough now so that we can all fly away from any possible trouble,” Worsel suggested.
“But that’s just exactly what we’re not going to do!” Kinnison declared, with finality. “Now that we’ve found a good charger, we aren’t going to leave it until our accumulators are chock-a-block. It’s coming in faster than full draft will take it out, and we’re going to get a full charge if we have to stand off all the vermin of Delgon to do it.”
Far longer than Kinnison had thought possible they were unmolested, but finally a couple of Delgonian engineers came to investigate the unprecedented shortage in the output of their completely automatic generators. At the entrance they were stopped, for no ordinary tools could force the barricade vanBuskirk had erected behind that portal. With leveled weapons the Patrolmen stood, awaiting the expected attack, but none developed. Hour by hour the long night wore away, uneventfully. At daybreak, however, a storming party appeared and massive battering rams were brought into play.
As the dull, heavy concussions reverberated throughout the building the Patrolmen—each picked up two of the weapons piled before them and Kinnison addressed the Velantian.
“Drag a couple of those metal benches across that corner and coil up behind them,” he directed. “They’ll be enough to ground any stray charges—if they can’t see you they won’t know you’re here, so probably nothing much will come your way direct.”
The Velantian demurred, declaring that he would not hide while his two companions were fighting his battle, but Kinnison silenced him fiercely.
“Don’t be a fool!” the Lensman snapped. “One of these beams would fry you to a crisp in ten seconds, but the defensive fields (they got anti-raygun force fields) of our armor could neutralize a thousand of them from now on. Do as I say, and do it quick, or I’ll shock you unconscious and toss you in there myself!”
Realizing that Kinnison meant exactly what he said, and knowing that, unarmored as he was, he was utterly unable to resist either the Tellurian (obsolete term for "Terran") or their common foe, Worsel unwillingly erected his metallic barrier and coiled his sinuous length behind it. He hid himself just in time.
The outer barricade had fallen, and now a wave of reptilian forms flooded into the control room. Nor was this any ordinary investigation. The Overlords had studied the situation from afar, and this wave was one of heavily-armed—for Delgon—soldiery. On they came, projectors fiercely aflame, confident in their belief that nothing could stand before their blasts. But how wrong they were! The two repulsively erect bipeds before them neither burned nor fell. Beams, no matter how powerful, did not reach them at all, but spent themselves in crackingly incandescent fury, inches from their marks. Nor were these outlandish beings inoffensive. Utterly careless of the service-life of the pitifully weak Delgonian projectors, they were using them at maximum drain and at extreme aperture—and in the resultant beams the Delgonian soldier-slaves fell in scorched and smoking heaps. On came reserves, platoon after platoon, only and continuously to meet the same fate, for as soon as one projector weakened the invincibly armored man would toss it aside and pick up another. But finally the last commandeered weapon was exhausted and the beleaguered pair brought their own DeLameters—the most powerful portable weapons known to the military scientists of the Galactic Patrol—into play.
And what a difference! In those beams the attacking reptiles did not smoke or burn. They. simply vanished in a blaze of flaming light, as did also the nearby walls and a good share of the building beyond! The Delgonian hordes having disappeared, vanBuskirk shut off his projector. Kinnison, however, left his on, angling its beam sharply upward, blasting into fiery vapor the ceiling and roof over their heads, remarking:
“While we’re at it we might as well fix things, so that we can make a quick get-away if we want to.”
Then they waited. Waited, watching the needles of their meters creep ever closer to the “full-charge” marks, waited while, as they suspected, the distant, cowardly-hiding Overlords planned some other, more promising line of physical attack.
Nor was it long in developing. Another small army appeared, armored this time, or, more accurately, advancing behind metallic shields. Knowing what to expect, Kinnison was not surprised when the beam of his DeLameter not only failed to pierce one of those shields, but did not in any way impede the progress of the Delgonian column.
“Well, were all done here, anyway, as far as I’m concerned,” Kinnison grinned at the Dutchman as he spoke. “My cans’ve been showing full back pressure for the last two minutes. How about yours?”
“Same here,” vanBuskirk reported, and the two leaped lightly into the Velantian’s refuge. Then, inertialess all, the three shot into the air at such a pace that to the slow senses of the Delgonian slaves they simply disappeared. Indeed, it was not until the barrier had been blasted away and every room, nook, and cranny of the immense structure had been literally and minutely combed that the Delgonians—and through their enslaved minds the Overlords—became convinced that their prey had in some uncanny and unknown fashion eluded them.

From GALACTIC PATROL by E. E. "Doc" Smith (1937)

"Bullets"

Some SF novels have postulated one-shot power modules. "Laser bullets" in other words.
In Norman Spinrad's Agent of Chaos, laser pistols were a ruby rod with a magazine full of "electrocrystals". Pulling the trigger caused the next crystal in the magazine to release its charge, that is, it was sort of a super-capacitor.
Robert Merrill envisions individual energy capacitors in a sort of "laser revolver". Capacitors can be re-charged at leisure, but a handgun can be rapidly re-loaded from a bandoleer of charged caps. Don't throw the spent capacitors away, they can be re-charged.
A .45 caliber cartridge is about 11.43 mm x 23 mm, which gives it a volume of about 2.4 cubic centimeters. At a rechargeable 2.5 kj/cm³ this means a battery the size of a .45 round would hold a good 6 kilojoules, enough for an extra-strength laser bolt.

ELECTRO-CRYSTALS

 Johnson drew his lasegun. The compact weapon, with its translucent sythruby barrel jutting out of its six-inch black ebonite handle, which contained the standard magazine holding fifty tiny electrocrystals each of which would give up the stored energy in its structure in one terrific burst of coherent light when the button trigger was pressed, could not be mistaken for anything innocuous.
Johnson pointed his lasegun outward, at the ring of Guards containing the crowd, pressed the trigger. A powerful beam of coherent light flashed from the barrel as the electrocrystal in the chamber gave up its energy and crumbled to dust.
The beam seared into the shoulder of at hulking, dark-skinned Guard. He screamed, writhed in pain, and fired instantly with his good right arm back in the general direction of Johnson.

From AGENT OF CHAOS by Norman Spinrad (1967)

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  Buck Rogers in the 25th Century (1938) Artwork by Dick Chalkins. Buck Rogers has disguised himself as a Martian Tigerman and has infiltrated the Martian invasion force. Note the carbonized remains of a disintegrated Martian on the floor, and the energy cell loading port in the top of the dis-ray pistol.

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  Laser revolver concept art by Robert Merrill
  click for larger image

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  Laser revolver by Robert Merrill
  click for larger image

In David Drake's Hammer's Slammers novels, the "powerguns" utilized an as-yet undiscovered scientific principle to instantly convert copper impregnated plastic wafers into a high-temperature bolt of plasma traveling at high velocity. Drake said all he wanted to do was postulate some hand-waving way of putting plasma bolts into bullets so he could write about futuristic soldiers.

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Lasers, though they had air-defense applications, were not the infantryman's answer either. The problem with lasers was the power source. Guns store energy in the powder charge. A machinegun with one cartridge is just as effective—once—as it is with a thousand-round belt, so the ammunition load can be tailored to circumstances. Man-killing lasers required a four-hundred-kilo fusion unit to drive them. Hooking a laser on line with any less bulky energy source was of zero military effectiveness rather than lesser effectiveness.
Science lent Death a hand in this impasse—as Science has always done, since the day the first wedge became the first knife. Thirty thousand residents of St. Pierre, Martinique, had been killed on May 8, 1902. The agent of their destruction was a "burning cloud" released during an eruption of Mt. Pelée. Popular myth had attributed the deaths to normal volcanic phenomena, hot gases or ash like that which buried Pompeii; but even the most cursory examination of the evidence indicated that direct energy release had done the lethal damage. In 2073, Dr. Marie Weygand, heading a team under contract to Olin-Amerika, managed to duplicate the phenomenon.
The key had come from spectroscopic examination of pre-1902 lavas from Pelee's crater. The older rocks had shown inexplicable gaps among the metallic elements expected there. A year and a half of empirical research followed, guided more by Dr. Weygand's intuition than by the battery of scientific instrumentation her employers had rushed out at the first signs of success. The principle ultimately discovered was of little utility as a general power source—but then, Olin-Amerika had not been looking for a way to heat homes.
Weygand determined that metallic atoms of a fixed magnetic orientation could be converted directly into energy by the proper combination of heat, pressure, and intersecting magnetic fields. Old lava locks its rich metallic burden in a pattern dictated by the magnetic ambiance at the time the flow cools. At Pelee in 1902, the heavy Gauss loads of the new eruption made a chance alignment with the restressed lava of the crater's rim. Matter flashed into energy in a line dictated by the intersection, ripping other atoms free of the basalt matrix and converting them in turn. Below in St. Pierre, humans burned.
When the principle had been discovered, it remained only to refine its destructiveness. Experiments were held with different fuel elements and matrix materials. A copper-cobalt charge in a wafer of microporous polyurethane became the standard, since it appeared to give maximum energy release with the least tendency to scatter. Because the discharge was linear, there was no need of a tube to channel the force as a rifle's barrel does; but some immediate protection from air-induced scatter was necessary for a hand-held weapon. The best barrel material was iridium. Tungsten and osmium were even more refractory, but those elements absorbed a large component of the discharge instead of reflecting it as the iridium did.
To function in service, the new weapons needed to be cooled. Even if a white-hot barrel did not melt, the next charge certainly would vaporize before it could be fired. Liquified gas, generally nitrogen or one of the noble gases which would not themselves erode the metal, was therefore released into the bore after every shot.

From HAMMER'S SLAMMERS by David Drake.

Gun as Power Supply

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In the original Star Trek episode "The Galileo Seven", Mr. Scott drains the energy out of a bunch of phaser pistols into the engines of the shuttlecraft. Doing some pointless calculations based on a very unscientific script we can hazard a guess at the energy content of a phaser pistol.
Some website I found claimed that a shuttlecraft was 17 metric tons. Assume that each crewmember is 68 kilos (150 pounds), this adds another 476 kilos for the seven crewmembers. The shuttle doesn't quite make orbit. As an upper limit, to make orbit would require a deltaV of around 8 km/s. Plugging this into the equation for kinetic energy gives us an energy requirement of about 5.6×10¹¹ joules. There appears to be six phaser pistols drained, so each phaser contains 5.6×10¹¹ / 6 = 9.3×10¹⁰joules.
How much is 9.3×10¹⁰ joules? Well, it is 9.3×10¹⁰ * 2.7778×10^-7 = 26,000 kilowatt-hours or 9.3×10¹⁰ / 4,500,000 = 21,000 kilograms of TNT. Well, let's face it, it takes lots of energy to vaporize an human being with one zap.

...Jaksan got wearily to his feet again. "I don't know. We can keep that in mind. It could be a lead, but I don't know." He lapsed into a deep study as they moved on but at the next halt he spoke with some of his old fire. "Dalgre, what was that process you told me about — the one for adapting disruptor shells for power?"
His assistant armsman looked up eagerly.
"It is." Within three words he had plunged into a flood of technicalities which left the rangers as far behind as if he were speaking some tongue from another galaxy. The Starfire might have lacked a mech-techneer, but Jaksan was an expert in his field and he had seen that his juniors knew more than just the bare essentials of their craft. ...
..."What do you propose to do?" Jaksan asked after a long moment.
"This process you were discussing with Dalgre, can you use disruptor charges in the sled? We must keep the extra fuel for emergencies."
"We can try to do it. It was done once and Dalgre read the report. Suppose we can, what then?"
"I'll take the sled and investigate that."...
...Jaksan was as good as his word. The next morning Dalgre, Snyn and the arms officer dismantled the largest of the disruptors and gingerly worked loose its power unit. Because they were handling sudden and violent death they worked slowly, testing each relay and installation over and over again. It took a full day of painful work on the sled before they were through, and even then they could not be sure it would really rise.
Just before sunset Fylh took the pilot;s seat, getting in as if he didn;t altogether care for his place just over those tinkered-with power units. But he had insisted upon playing test pilot.
The sled went up with a lurch, too strong a surge. Then it straightened out neatly, as Fylh learned how to make adjustments, and sped across the river, to circle and return, alighting with unusual care considering who had the controls. Fylh spoke to Jaksan before he was off his seat.
"She has a lot more power than she had before. How long is it going to last?"
Jaksan rubbed a grimy hand across his forehead. "We have no way of telling. What did that report say, Dalgre?"...

From Star Rangers (aka The Last Planet) by Andre Norton (1953).

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  Field Effect Weapon. Prop prototypes designed and created by Clyde R. Jones for the Gene Roddenberry's unproduced TV show concept "Starship".

Laser Power Output

Laser Power
<2 milliwatts	Class 1 laser. Harmless
2 milliwatts	Class 2 laser. Harmless
5 milliwatts	Class 3R laser. Mostly harmless. Laser pointers
30 milliwatts	Class 3B laser if wavelength 400 to 700 nm pulsed. Needs protective eyewear
400 milliwatts	Red DVD burner x24 Dual Layer Speed Recording
0.5 watts	Class 3B laser if wavelength 315 nm to far infrared continuous. Needs protective eyewear. Medical laser for cosmetic procedures
>0.5 watts	Class 4 laser. Needs protective eyewear and protection from burns and igniting combustible material.
0.7 watts	Blu Ray DVD burner x12
5 watts	Beam capable of lighting your cigar or burning wood
30 watts	Low-powered CO2 laser
60 watts	Laser light show at a rock concert
100 watts	CO2 laser used in surgical procedures
200 watts	Industrial CO2 laser
1 kilowatt	Beam capable of cutting metal plates
30 kilowatts	US Navy's Laser Weapon System (LaWS) Solid State Laser (SSL) Directed Energy Weapon (DEW)
50 kilowatts	German point-defense laser system
100 kilowatts	US military's MILSPEC directed energy weapon for tactical targets. "Weapons-grade Laser"
200 kilowatts	Dr. Schilling's sidearm: 1 kJ divided into 1000× 1 J pulses at 5 μs intervals
1 megawatt	US military's MILSPEC directed energy weapon for strategic targets. Goal of Strategic Defense Initiative spaceborne laser. Approximate power level of the Boeing YAL-1.
5 megawatts	Luke Campbell light laser pistol: 1.2 kJ divided into 60× 20 J pulses at 4 μs intervals
20 megawatts	Luke Campbell battle laser: 10 kJ divided into 50× 200 J pulses at 10 μs intervals
0.25—2.4 gigawatts	Fictious Attack Vector: Tactical starship laser turrets

Cooling

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  Paladin's stun gun
  Note large heat radiators
  Artwork by the legendary Eliot R. Brown for Official Handbook of the Marvel Universe #15 (1984)
  Image scan from Eliot R. Brown Comically Technical blog

 Lasers are notoriously inefficient. Figure as a rule of thumb the efficiency of a near-future laser weapon will range from 20% to 50% (currently they are more like 7% to 15%). So at the low end, in order to emit a 1 kilojoule bolt the laser will require 5 kilojoules of energy, and will have to somehow get rid of 4 kilojoules of waste heat. This will be much easier if the weapon is to be used on Terra or another planet with an atmosphere. A weapon desgned for use in space is going to need lots of heat radiator fins.

And you'll need some serious cooling. I'd go with liquid-metal microchannel heat pipes etched into all the hot surfaces, and leading to cooling fins around the "barrel". If you use the chemical-propellant option, regenerative cooling could also work.

en note: "regenerative cooling" is where the cold liquid chemical fuel is used as coolant for the reaction chamber, right before it is fed into the chamber to be burnt for power.

Dr. Schilling

I recently asked this question to master game designer, and all around great human being Ken Burnside, who is creative director of Ad Astra Games:
Ken Burnside: "You'll also have the not-so-trivial task of not cooking the hands of the person using the weapon."
"When you fire a bullet from a rifle, about 80% of the chemical energy imparted to the projectile sends it downrange. The remaining 20% is waste heat, ejected in the form of hot brass. The waste heat rejection issue is also why caseless ammo never really took off. In round numbers, a typical .223 (5.56mm) round delivers (975²) * 0.0035 kgm/sec energy or about 3.3 kilojoules of energy to the target. It's dumping about .05 kilojoules in waste heat and hot gasses."
"Right now, lasers are about 7-15% efficient. For the sake of numbers, we'll call it 12.5%. That means that for every kilojoule you're delivering to the target, you'll need to get rid of 7 kilojoules of waste heat. Very roughly, cooking a 9oz New York Strip steak to medium-rare is about one kilojoule."

from FWS ARMORY: LASERS: THE KILLER LIGHT by William (2014)

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  Prop imperial stormtrooper blaster used in the first two Star Wars movies

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  Laser Rifle from Lost in Space

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Targeting

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  This is not quite the reflex sight Dr. Schilling is talking about.

GYROSTABILIZED1, REFLEX SIGHT1

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  reflex camera

With penetration, range, and repeatability dealt with, it is time to turn to accuracy. Lack of recoil, automatic fire capability, and line-of-sight accuracy are all major assets here, but there is one more improvement to be made. Both lasers and particle beams can be steered at least a degree or two off-axis, in the case of the laser via the adaptive-optic mirror, for particle beams with a transverse magnetic field at the muzzle.
If we can throw in a chip-mounted laser or acoustic gyro set, we can have a gyrostabilized handgun. The weapon shoots not at where the gun is pointed at the instant of firing, but at a weighted average of where it has been pointing over the past quarter of a second or so. Smoothes out a lot of the jitter inherent in human marksmanship.
You'd probably want to integrate this feature with the weapon's sights. A reflex-type optical sight could have an LED display linked to the gyrostabilizer, rather than a fixed reticule. The dot, or crosshairs, would then indicate the actual shot path and would remain similarly stable under jitter.

(ed note: "Reflex" in this context refers to the viewfinder on a reflex camera. A mirror allows the viewfinder to use the actual camera's optics. The user literally sees the exact image which will be captured on film. When the shutter is tripped, the mirror moves out of the way and allows the image to fall on the film. So in Dr. Schilling's concept, the shooter would aim through the laser pistol's optics, the same optics that will direct the weapon's beam.)

Dr. Schilling

REFLEX SIGHT2

Another interesting thing is that you could use the beam optics for your scope. Just install a switchable mirror that flashes reflective for the millisecond the beam is on, and you could then direct the light from your target that comes into your weapon's optics straight into an eyepiece. You could see exactly where the beam would strike without having to make any allowances for parallax or beam deflection (since the incoming light would be deflected along exactly the same path as the outgoing beam). Thus, no separate lens for a scope, sitting on top of the gun.

Luke Campbell

IRON SIGHT, LASER DOT, REFLEX SIGHT3

While using the laser's optics as a scope is pretty clever, a quicker type of sight will be needed for close in shots. Iron sights or some type of collimating sight (e.g. red dot sight, holographic sight) strapped to the top will do well.
Another clever one would be to use the laser's optics to project a laser sight. Pull the trigger, and the harmless red dot suddenly explodes. BANG!

(ed note: this will be even more accurate than a laser dot sight for a conventional slugthrower firearm. Laser dot is guaranteed to be parallel to laser weapon beam since it is using the exact same optics. Unlike bullets, weapon laser beams are not subject to bullet drop and windage. Target mobility while the bullet travels is also not a factor since the target is unlikely to be moving at a high fraction of the speed of light. The weapon laser beam will hit exactly where the red dot is resting.)

Using the laser optics as a scope would be more useful for long range or high accuracy shots.

James Borham

GYROSTABILIZED2

In combat, I would expect such a weapon to be used in automatic fire mode at ~10 Hz. With fifty to a hundred pulses to play with, you won't run out of ammunition too soon as is the case with current machine pistols. And recoilless, stabilized automatic fire should allow a moderately capable marksman to walk a burst on target in one or two reaction cycles (say, half a second) in most circumstances. Imperial Stormtroopers ^(tm) could no doubt still find a way to miss with such a weapon at ten meters, but not competent soldiers. Practical combat range, if you don't mind missing a good part of the time, would be on the order of 50 meters

Dr. Schilling

I will also note that there currently exists a species of "scope through the gun barrel" piece of gear for conventional slug-throwing rifles, the EOP system.

 As it turns out, the Phaser type-I from the classic Star Trek TV show had a reflex aimsight. Turning the dial on the top would raise the acrylic aimsight. This would also work with the type-II pistol phaser, since that incorporates a type-I phaser. 

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  From an episode of Star Trek TOS

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  Original hero phaser prop from Star Trek TOS
  Photo by Greg Jein

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  crafted by Karl Tate

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  crafted by Karl Tate

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  crafted by Karl Tate

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  crafted by Karl Tate

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  Original hero phaser prop from Star Trek TOS
  You can faintly make out an Eveready AA battery
  Image from The Making of Star Trek (2968)

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  Original hero phaser prop from Star Trek TOS
  Copper clips are for a AA battery. This feeds a grain-of-wheat light bulb in the barrel. The light assists the special effect artists when they matt in the phaser beam.
  Photo by Greg Jein

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  Original hero phaser prop from Star Trek TOS
  Photo by Greg Jein

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  Phaser 1 attached to Phaser 2 handgrip. Reflex aimsight deployed.
  Note velcro strip on Phaser 1, hopefully invisible while filming.
  Original hero phaser prop from Star Trek TOS
  Photo by Greg Jein

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  Phaser 1 attached to Phaser 2 handgrip. Reflex aimsight deployed.
  From Star Trek TOS episode The Man Trap

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  Reflex aimsight on a Phaser 1 from Star Trek: Discovery
  Similar to Star Trek TOS, but different

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  In the 1967 TV show "The Invaders", the sidearms used by the sinister aliens had a reflex sight.

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  From "The Invaders".

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  From "The Invaders".

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  Artwork by Ed Emshwiller for Venture Science Fiction September 1957.

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  detail

Wavelength

Band	Wavelength (m)
Far Infrared	1e-3 to 5e-5 m (1,000,000 to 50,000 nanometers)
Mid Infrared	5e-5 to 2.5e-6 m (50,000 to 2,500 nanometers)
Near Infrared	2.5e-6 to 7.5e-7 m (2,500 to 750 nanometers)
Red	7.5e-7 to 6.2e-7 m (750 to 620 nanometers)
Orange	6.2e-7 to 5.9e-7 m (620 to 590 nanometers)
Yellow	5.9e-7 to 5.7e-7 m (590 to 570 nanometers)
Green	5.7e-7 to 4.95e-7 m (570 to 495 nanometers)
Blue	4.95e-7 to 4.5e-7 m (495 to 450 nanometers)
Indigo	4.5e-7 to 4.2e-7 m (450 to 420 nanometers)
Violet	4.2e-7 to 3.8e-7 m (420 to 380 nanometers)
Ultraviolet A	4e-7 to 3.15e-7 m (400 to 315 nanometers)
Ultraviolet B	3.15e-7 to 2.8e-7 m (315 to 280 nanometers)
Start of Vacuum Frequencies	2.e-7 m (200 nanometers)
Ultraviolet C	2.8e-7 to 1e-7 m (280 to 100 nanometers)
Extreme Ultraviolet	1e-7 to 1e-8 m (100 to 10 nanometers)
Start of Ionizing Radiation	1e-8 m (10 nanometers)
Soft X-Ray	1e-8 to 2e-10 m (10 to 2e-1 nanometers)
Hard X-Ray	2e-10 to 2e-11 m (2e-1 to 2e-2 nanometers)
Gamma-Ray	2e-11 to 1e-13 m (2e-2 to 1e-4 nanometer)
Cosmic-Ray	1e-13 to 1e-17 m (1e-4 to 1e-8 nanometers)

There is a list of various real-world lasers and their lasing frequencies here.
Note that wavelengths shorter than 200 nanometers are absorbed by Terra's atmosphere (so they are sometimes called "Vacuum frequencies") and anything shorter than 10 nanometers is considered "ionizing radiation" (i.e., what the an average person on the street calls "atomic radiation").
The cornea, lens, and vitrous humor of the eye are transparent to wavelengths between roughly 0.35×10^-6 and 1.4×10^-6 meters, lasers using these wavelengths can cause blindness.

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Far infrared is a poor choice. Rapidly blocked by moisture in the air, and there are very few materials you can make a laser window out of (single large salt crystal or expensive high-tech materials). The wavelength is long enough that diffraction makes it difficult to focus. The only reason to use it is if you are on a budget, since 10,600 nanometer CO₂ industrial lasers are common and cheap.
Mid Infrared has most of the same problems as far infrared. The US military has built a few been deuterium fluoride chemical lasers with a wavelength of 3,800 nanometers.

Near Infrared is a desirable wavelength for lasers to be used in Terra's atmosphere. There are quite a few frequencies that the atmosphere is totally transparent to: around 2500 nanometers and the band from 1200 to 700 nanometers. The best is 1000 nanometers because it will go through pretty much anything that is transparent to visible light. The ALP turret used chemical oxygen iodine lasers lasing at 1315 nanometers. Neodymium lasers lase at 1060 nanometers. Titanium sapphire laserslase from 1100 to 800 nanometers.

Visbile Light is desirable since by definition the laser beam can pass through anything that is transparent. It does not attenuate in the atmosphere much, and it focuses more sharply than infrared. Thre is a problem with atmospheric twinkle. Of course one of the drawbacks of lasers using visible frequencies is that the laser is visible to the human eye, especially at night. When the beam hits something there will be a laser-light-show flare. If there is dust, fog, or something in the air the beam will be visible.
There are no known lasing mediums that can make high powered visible light lasers, but that doesn't mean there are none. Feel free to use them in science fiction. Certain crystals can double the frequency of light passing through them. Lithium triborate is sometimes used to frequency-double a Nd:YAG 1064 nm infrared laser beam into a 532 nm green laser beam. If you are going to be firing a laser underwater, you should use blue or green or the beam won't get very far before it is absorbed.
Near Ultraviolet can be focused to a smaller spot size than infrared or visible light. Drawbacks include attenuating faster in air, can ionize the air producing a glowing trail, the frequences are blocked by the ozone layer making orbital bombardment impossible, and ultraviolet shorter than 200 nanometers are vacuum frequencies blocked solid by atmosphere. It cannot penetrate window glass but quartz is transparent to UV.
Lasers using vacuum frequencies are Ray Beams. Lasers using frequencies longer than 200 nanometers are either Heat Rays or Blasters.
Extreme ultraviolet is difficult to make into a laser since there is nothing transparent to EUV that can be used as a window or a lens, normal mirrors do not work, and grazing mirrors work poorly (70% reflection, tops). Thus it is hard to focus the blasted rays. On the plus side they can focust to a tiny spot size and they are penetrating as all get out. The exact frequency determining the border between extreme ultraviolet and soft x-rays is nebulous.
Soft x-rays have all the advantages and drawbacks of extreme ultraviolet, but more so.
Plus one advantage: frequencies below 10 nanometers are ionizing radiation (nuclear radiation), so biological targets will also be suffering from radiation sickness.
Plus two more problems: the mirrors cannot have any imperfections larger than 10 atoms, and there isn't any good source of soft x-rays to pump the laser with (short of a fission bomb).
Hard x-rays have all the advantages and drawbacks of soft x-rays, but more so. Plus one drawback: grazing mirrors do not work at all, youh ave to use x-ray crystal diffraction to make a diffractive resonant cavity.
Gamma-rays have all the advantages and drawbacks of hard x-rays, but more so. Plus one drawback: there is no known way to focus gamma rays. The only gamma-ray laser proposal uses gamma-rays from a nuclear detonation and just tries to use gamma rays that happen to be moving in the right direction.

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In the chart below, you can see the vulnerability of various parts of the human body to various laser frequencies. Hemoglobin is blood. Melanin is skin and hair. Water is all body tissue. Scatter is the molecular bonds holding proteins together.

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  Chart from ShoreLaser

As a point of detail: see that blue water line? That shows wavelengths to not use, because it means atmospheric water vapor is opaque at those wavelengths. Also, light that is transmitted through flesh or is scattered internally will still typically wind up being absorbed in the end.
Once you have a reasonably deep hole (fairly high aspect ratio) absorption will be essentially 100% regardless of wavelength — light that is scattered or reflected will often not bounce straight out of the hole, giving it a chance to be absorbed by the sides of the hole. This won't help with penetration, but will make the hole bigger.

Anthony Jackson

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So lets take a hypothetical laser sidearm, assume a 10cm lens, 10kW output power, 1ms beam duration, and 0.5 duty cycle. Given these as constant, but varying the wavelength of the laser, we get the following penetration on a carbon target at the listed ranged:

7e-7 m (Near infrared)
Range	Penetration
25m	6.25mm
50m	0.78mm
100m	0.10mm
200m	0.01mm

5.5e-7 m (Green)
Range	Penetration
25m	12.88mm
50m	1.61mm
100m	0.20mm
200m	0.03mm

4.3e-7 m (Indigo)
Range	Penetration
25m	26.96mm
50m	3.37mm
100m	0.42mm
200m	0.05mm

3.2e-7 m (UVA)
Range	Penetration
25m	65.4mm
50m	8.18mm
100m	1.02mm
200m	0.13mm

It's obvious that as wavelength decreases, neglecting atmospheric effects, damage on the target increases. So the question is, how low can I push my wavelength, and what are the effects? If 90% of the UVA beam is scattered, then it is equivalent to the infrared beam. If only 50%, it is superior.
Seems like an important point to figure out. Does anyone have a good model? I've been digging on scholar.google.com to no avail.

Eric Rozier

Hm. Not sure how you're getting penetration.
Actually, it's penetration that increases, not damage. In any case, the practical limits for laser weapons are as follows: 1) We have very limited ability to generate high power short wave lasers. 2) Beyond a certain energy density, air breaks down and becomes opaque due to nonlinear effects. I'm not sure exactly how this scales with wavelength, but I'm pretty sure shorter wavelength is worse.
Factor (1) tends to produce lasers in the 800-1000 nm range. Factor (2) doesn't generally limit modern lasers, but is a real issue for small arms lasers.

Anthony Jackson

Anthony Jackson: Hm. Not sure how you're getting penetration.

From the equations on the Atomic Rocket website. As I said, assuming a Carbon target.

(ed note: he even made an online calculator)

Anthony Jackson: Actually, it's penetration that increases, not damage.

Not sure how you figure that. At 7×10^-7m, we vaporize 2.23×10^-8m³ of carbon at 25m. At 4.3×10^-7m, we vaporize 3.61×10^-8m³ of carbon at 25m.
Both damage and penetration increase.

Anthony Jackson:
1) We have very limited ability to generate high power short wave lasers.
2) Beyond a certain energy density, air breaks down and becomes opaque due to nonlinear effects. I'm not sure exactly how this scales with wavelength, but I'm pretty sure shorter wavelength is worse.

Factor 1 disappears with less handwavium than it takes for an MFT (magic fusion torch spacecraft), so I'm not terribly concerned with it. While X-rays have some inherent problems, we can and do make cheap UV lasers right now, and there seems to be no reason why we can't up their power significantly.
Factor 2 is definitely an issue for small arms lasers, but at what point does it become a problem? What is the wave length at which we get the most bang for the buck? How bad is it at various wave lengths? Surely a model exists somewhere.

Eric Rozier

A lower limit on wavelength in oxygen atmospheres is somewhere around 150 to 200 nanometers. Below this you get single photon absorption by an electronic transition — this means your beam gets absorbed very fast.
For femptosecond pulses when you get self-focusing, you can get so called supercontinuum light, where the monochromatic light of the laser gets scattered into white light across a range of wavelengths. Self focused filaments can propagate for ten meters at least, and the primary absorption is in the plasma core of abut 0.1 mm across, indicating that air can handle gigawatt power levels across most of the visible spectrum across areas of more than 0.01 mm².
Another data point is that 0.193 micron light (193 nanometers) at 50 GW/m² will fall off with distance R as approximately exp(-R/100 m) due to two photon absorption.
If I'm not concerned about civilian eye safety and I don't care if the bad guys can see where I am, visible green is probably a pretty good wavelength to use for long distance lasing — it focuses well compared to longer wavelengths but doesn't suffer much from atmospheric Rayleigh scattering like shorter wavelengths. Details on calculating Rayleigh scattering can be found here
http://panoptesv.com/SciFi/LaserDeathRay/LinAbs.html
Since you are describing a pistol, however, you probably don't care about long range targets. In this case you might consider using nanosecond to femptosecond pulses, causing damage by producing power levels high enough to explode a small part of the target, thus causing mechanical damage through the shock wave rather than direct heating. Now the range depends more on your instantaneous intensity. Some rough details can be found at
http://panoptesv.com/SciFi/LaserDeathRay/Blaster.html
http://panoptesv.com/SciFi/LaserDeathRay/DamageInstant.html
In this regime, you can also use self focusing and filamentation to increase your depth of field so you can penetrate your target right through at close range
http://panoptesv.com/SciFi/LaserDeathRay/DepthOfField.html
http://panoptesv.com/SciFi/LaserDeathRay/SelfFocus.html

Luke Campbell

Spot Size and Brightness

• 

An important feature of the laser is the "spot size". This is the tiniest dot the laser can focus the beam down to. Dr. Schilling's laser has to focus the spot size to less than a millimeter. The spot size depends upon the wavelength of the beam, the radius of the lens or mirror at the muzzle, and the range to the target. Remember that a spot 1 millimeter in diameter has a radius of 0.0005 meters.
R_T = 0.61 * D * L / R_L
where:

• R_T = beam spot radius at target (m)
• D = distance from laser emitter to target (m)
• L = wavelength of laser beam (m, see table)
• R_L = radius of laser lens or reflector (m)

Don't forget to double the spot radius in order to get the spot diameter.

If you want to find the "effective range" of the laser, you take the desired spot radius, weapon lens radius, and weapon laser wavelength:
D = ( R_T * R_L ) / ( 0.61 * L )
Looking at the equation you can see that to increase the effective range, you have to make the wavelength L shorter, the lens/reflector radius R_L larger, or both. You want the spot size to stay put.
To calculate the "brightness" or energy density of the spot:
B_PT = B_P / ( π * R_T²)
where:

• B_PT = energy density of the spot (Joules/m²)
• B_P = laser energy at emitter (Joules)

Laser Muzzle

• 

Business end of a laser pistol?

Winchel Chung
I'm a little fuzzy on what the muzzle of a laser pistol would look like
Dr. Schilling's laser has to focus the spot size to less than a millimeter. He says that at a guess, a pistol could not have a focusing mirror larger than, say, 5 centimeters in diameter, which would restrict the effective range to about 60 meters.
Question: how do you vary the focus with a mirror? Does the mirror have to have a variable geometry, or do you just alter the distance between the emitter and the mirror?
Would the laser pistol muzzle look like the ALP turret, or like the lens on a camcorder, or like something totally different?

• 

  ALP turret

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  Ancient film camcorder

---

Isaac Kuo
You can just alter the distances of the optics.
For John Schilling's laser pistol, I'd guess that maybe the beam generator would have a diameter of 10mm, so the laser cavity optics suffer only 1/100 the intensity of the light on the target (1mm diameter spot). The highly reflective dielectric mirrors would only absorb maybe 1/1000 as much light as the target would absorb, so the intensity of the absorbed light would only by 1/100,000 as much as the target suffers.
It might look something like this:

• 

However, such an exposed mechanism would get dirty and would be difficult to keep clean. Thus, the muzzle would be protected by a shroud with a clear flat circular window. This window would be much easier to wipe clean.

---

Luke Campbell
I always figured it would look like a camera lens. Maybe several camera lenses, for focusing at targets at long, medium, and short ranges, and the beam switched to the lens most appropriate to the target range.

• 

Question: how do you vary the focus with a mirror? Does the mirror have to have a variable geometry, or do you just alter the distance between the emitter and the mirror?

Either would work, though the latter is simpler (although maybe slower). Note that the "emitter" should be a diverging beam (so may in fact be the focal point of a mirror that diverges the beam that comes nearly parallel out of the laser).

Would the laser pistol muzzle look like the ALP turret, or like the lens on a camcorder, or like something totally different?

The airborn laser turret would be appropriate for something that aimed itself. This would probably not be called a pistol (but would be really scary). Something designed to be pointed with a human hand and arm would have a fixed lens or mirror. If using a mirror, I expect it would protect the mirror with a window. So either a lens or mirror ends up looking like a camcorder or camera lens or some such.

---

David McMillan
If my experience is any guide, the field kit for such a weapon will require at least a few spare "window" glasses — even with the beam diffuse as it passes through the final optics, at these power levels a speck of dirt on the window can create a burn spot on the glass, which will absorb some of the beam energy and become larger, absorbing more of the beam, and so on. The performance drop is roughly asymptotic.
The field kit should probably also include at least one spare lens, just in case — some fumble-fingered grunt is sure to drop the weapon and crack the lens while they have the window unit detached for cleaning/replacement. On the systems I've built, the lenses usually ran ~$500 and the post-lens window glasses ~$30.
Whichever way you go, though, a near-optical laser weapon is going to raise the military mania for clean weapons to unprecedented heights.

---

Stephen Rider
Can we slap an iris on the ends of these suckers? Means you'd need an aiming port, but I know first hand how much dust you can get on digital optics just from changing a camera lens in a dusty room that an extra level of protection would be VERY useful.

---

Isaac Kuo
The iris can be made of clear plastic so it can be used for optics or to fire an "aiming dot". Its acceptable for the iris to get a little dirty. Upon firing, the iris slides out of the way to reveal the clean window underneath.
Perhaps the window behind the iris could have a number of layers. If the outer layer gets too dirty to wipe clean, you peel it off.

Business end of a laser pistol? from sfconsim-l (2007)

Triple Turret

 If the business end of the laser is not sophisticated enough to have a wide range zoom lens, it might have a lens turret with multiple lenses. The turret is rotated to engage the lens appropriate for the target's distance band (long, medium, or short).

I always figured it would look like a camera lens. Maybe several camera lenses, for focusing at targets at long, medium, and short ranges, and the beam switched to the lens most appropriate to the target range.

Luke Campbell

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Real world movie camera triple-turret lenses

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• 

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• 

---

Triple-turret lenses in science fiction.

• 

  ST:TOS Laser Pistol
  Old-style laser pistol from ST:TOS The Cage

• 

  ST:TOS Laser Pistol
  Number One sets the laser to detonate by a forced-chamber explosion

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  ST:TOS Laser Pistol

• 

  ST:TOS Laser Pistol
  crafted by Karl Tate

• 

  ST:TOS Laser Pistol
  crafted by Karl Tate

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  ST:DIS Phaser Pistol

• 

  ST:DIS Phaser Pistol

• 

  ST:DIS Phaser Pistol

• 

  ST:DIS Phaser Pistol
  image from Startrek.com

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  ST:DIS Phaser Pistol
  Bottom lens is probably active lens, since it is on the center-line
  image from treckmovie.com

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  ST:DIS Phaser Pistol
  image from Jonathan Frakes

• 

  ST:DIS Pulse Rifle
  image from Startrek.com

• 

  ST:DIS Pulse Rifle
  image from treckmovie.com

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  ST:DIS Pulse Rifle
  image from jvancitters

Lasers In Practice

• 

If one is using this information in order to write an SF novel, the question comes up of what will an observer see and hear during a laser pistol battle. Luke Campbell has the information.

What would it sound like?

The actual mechanism of producing the laser beam could sound like anything, from complete silence, to the click of an electrical contact, to a sharp, electric snap, to a gunshot-like thunderclap.
The beam, when incident upon its target, will make a nice bang.

The pistol won't make a "zap" sound, will it?

If the beam is repeated rapidly it might, however, make a buzz. It might end up sounding quite electrical at a few hundred Hertz.

Will it be too quiet to hear or will be loud enough to cause hearing loss? Will it sound like an extended explosion as the series of steam detonations bore a hole?

Remember that the temporary cavity caused by the explosions only lasts a few milliseconds, so the beam has to have completed its work of piercing the target at this time. The individual explosions will be too closely spaced (microseconds apart) to be individually audible. Since shocks are always supersonic to the air in their path, and subsonic to the moving air left behind them, multiple subsequent shocks from the same source tend to merge into one stronger shock. Thus, each pulse probably makes one bang. The bang comes from a series of explosions whose total energy is about the same as that of the gunpowder detonating in a firing rifle, so it will probably be about as loud.

What would the beam look like?

This depends on a number of things. If the beam is in the visible part of the spectrum, you get a noticeable path through clean air at indoor lighting intensities. I am not sure if it will be visible out of doors under full sunlight, but you could see it at night. The beam will be widest at the aperture of the gun, probably a few centimeters across to keep the optics from being damaged by the intense light. The beam will converge to a spot a millimeter or so across at the target. In unclean air, the beam will be a lot more visible. This Rayleigh scattering is linear, so the total integrated brightness across the cross section of the beam should be constant, if we neglect the gradual attenuation of the beam due to the light being scattered out of it. Higher frequency light scatters much more than lower frequency light, so a blue beam would be much more visible than a red one.
When a visible beam is incident on the target, it creates a very bright flash of the same color as the beam. This may temporarily dazzle those looking at it, and the beam itself may be overlooked because of the bright flash obscuring it.
If the weapon lases in the UV, the intense pulse may cause multi-photon ionization of atoms in the air, causing a fluorescent glow along the path of the beam (possibly red, green, or violet, I'm not quite sure what sparsely ionized air at atmospheric pressure looks like). Since this process is non-linear, it will be dimmest near the aperture where the beam is widest, and most intense nearer the target. Weapon designers will probably try to minimize this effect, since it leads to attenuation of the beam and subsequent loss of effectiveness.
Near IR beams are likely to only be visible if there are relatively large pieces of dust, lint, or pollen floating around, which will glow incandescent as they burn under the irradiation of your beam. I doubt beams in the "thermal" IR range would be used, even though the air is fairly transparent to these wavelengths, because with short, intense pulses you tend to get cascade ionization with these lower frequencies, and this will completely absorb the beam.
Beams at non-visible frequencies will also make a flash and a bang where incident on the target from the expanding plasma of their explosion, but nowhere near as bright as that of a visible beam.
In vacuum, of course, the beam itself is always invisible, but you can still see the flashes at the target.

Luke Campbell

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  Surgical laser, Fantastic Voyage (1966).

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  Surgical laser, Fantastic Voyage (1966).

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  Masters of the Universe (1987).

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  Noisy Cricket, Men In Black (1997).

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• 

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  Artwork by Kohn for Amazing Stories, May 1926

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  Note the ring sight
  Artwork by Earle Bergey "inventor of the brass brassière" for Thrilling Wonder Stories February 1949

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  Artwork by Robert Gibson Jones for Amazing Stories November 1943

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  Artwork by Kelly Freas for Astounding Science Fiction April 1954

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  Artwork by Kelly Freas for Science-Fiction Adventure Books No. 11 Spring

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  Artwork by Kelly Freas for Astounding Science Fiction "The Pirates of Ersatz"

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  Artwork by Kelly Freas for Science-Fiction Adventure Books No. 9 summer

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  Artwork by Kelly Freas for Astounding Science Fiction "Hiding Out"

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  Artwork by Kelly Freas for Future Science Fiction No. 33

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  Detail: Artwork by Kelly Freas for Future Science Fiction No. 33

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  Artwork by Kelly Freas for The Lion Game (1971)

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  detail

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  Artwork by Kelly Freas for Worlds Of Science Fiction April 1956

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• 

  Colt-Vickers atomic fission rifle, Forbidden Planet (1956). Note that the world "rifle" is a misnomer here, since the weapon not only lacks rifling inside its barrel, it lacks a barrel as well.

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  Buck Rogers TV show (1977).

What would the Asteroid Pirate look like after they got hit?

The method of subsequent explosions on the back of an expanding cavity driving the cavity through the target will leave a wound much like that of a gunshot, except without fun stuff like the bullet fragmenting or breaking up. A variant where nearly parallel beams a few cm apart literally rip the tissue between them could leave a wound looking more like an ugly gash - add on a few more of these beams on the same plane and you could literally cut someone in half with one millisecond pulse, using only about as much energy as goes into accelerating the bullet of a modern day battle rifle. (ed note: in some SF novels by E.E."Doc" Smith and Robert Heinlein, this is referred to as setting your sidearm to "fan beam".)

Will there be a large splash of blood and gore on the wall behind the unlucky pirate?

Quite likely, Note that since you do not have the momentum associated with a projectile, it will be more spread out than you would get from a gunshot wound, and you would get blood and gore coming out the front, too.

I assume that since the beam is one millimeter in diameter but the hole in the pirate is four centimeters, little or no wound cauterization will occur.

Nope, the wound would be ragged and messy. It is created by mechanical, not thermal effects.

Luke Campbell

Laser Blindness

• 

• 

  Artwork by Robert Amundsen for Jack Williamson's Trapped In Space

• 

  Laser safety goggles

• 

  Personnel Halting and Stimulation Response rifle

 As I already stated, pretty much no science fiction in movies, TV or novels mentions the blindness hazard of laser sidearms (with the possible exception of Jack Williamson's Trapped In Space). On Terra, anybody within about five kilometers (i.e, the horizon) of an operating laser weapon is at risk of loosing their eyesight permanently. If the beam flicks over a window, a shiny automobile, or anything else reflective (reflected or scattered light); an innocent bystander will suddenly require the services of a working dog. People knowingly entering a laser gun battle will be wearing anti-laser goggles (or contact lenses). Laser gunmen who care about innocent bystanders will use lasers of frequencies opaque to the cornea of the eye. That means either greater than 1400nm (infrared to microwave) or less than 400nm (ultrviolet to x-ray). In other words, a frequency other than the rainbow colors of visible light.
There is a laser safety classification system. Class 1 is safe for eyesight. Class 1M is safe as long as you are not looking at the laser through a magnifying glass or telescope. Class 2 is safe for eyesight due to the human blinking reflex (most laser pointers fall into this catagory). Class 2M is safe with no magnifying glasses or telescopes. Class 3R are mildy dangerous. Class 3B are dangerous but diffuse reflection is not (laser protective goggles required). Class 4 are incredibly dangerous, since it will also burn holes in clothing and skin (laser protective goggles required). Naturally all laser weapons are class 4.

Will the beam be invisible or bright enough to be blinding?

It is quite likely to be both. The beam itself may be invisible or minimally visible, but if even a tiny fraction of the beam is specularly scattered into your eye, near IR and visible and some near UV will be focused to a diffraction limited spot on your retina, causing burns and permanent scarring. This can lead to degradation of vision or total blindness. Interestingly, the brain compensates for blind spots on the retina, so that you might have lost up to 60% of your vision from multiple exposures to beams and you still think you can see just fine. Also interestingly, the fluid in our eyes can cause a small amount of non-linear upconversion of intense coherent light that passes through it, so when directly exposed to a near IR beam, you may actually see it as two IR photons are combined into one visible photon with twice the frequency. Some people who have been blinded by pulsed neodymium lasers (which lase at around 1 micron near IR) have reported that the last thing they ever saw was a green flash (green, at 0.5 micron, has half the wavelength and twice the frequency of the 1 micron neodymium line).
Anyone likely to be using a laser will probably wear protective goggles or contacts. With today's technology, you would probably make them out of an optical band gap material that excludes a very narrow window of light centered on the laser's frequency. This means that the people who fired the lasers would not be able to see the beams or flashes of their own weapons (assuming they used visible light lasers). They would still see the flashes from the plasma explosions, though, plus incandescence of suspended atmospheric particles and fluorescence from multi-photon absorption.

Luke Campbell

Luke has more details about laser eye . Below is a sample:

Any death ray worth its name will be sufficiently intense that anyone looking directly into the beam will be instantly blinded (if not killed — it is, after all, a death ray). There are, however, other vision hazards. The cornea, lens, and vitrous humor of the eye are transparent to wavelengths between roughly 0.35×10^-6 and 1.4×10^-6 meters. If a small fraction of a death ray beam in this wavelength range is specularly reflected off a smooth surface, anyone looking at that surface will focus the reflected light into a tiny spot on their retina. This can heat the retina up enough to cause a third degree burn, leading to a spot of permanent blindness. Very powerful lasers (such as just about any death ray) can still be hazardous after mutliple specular reflections — the fraction of the beam that reflects off the target might bounce off a shiny hubcap, reflect off a window, and then reflect off the shiny paint job of a passing car to blind a bystander.

Luke Campbell

Suppose our weapon users want to minimize the effect on potential innocent bystanders, or are worried about having to fight without their optical protections. What would be the best way to make such a laser weapon so that bystanders/unshielded users were not blinded?

Johnny1A

You could use a weapon that emits a beam at frequencies that are mostly absorbed by the lens or vitreous humor. I seem to recall that laser light at 1.5 microns near IR and longer wavelengths are largely absorbed by the eye before any of it can get to the retina. At the other end of the spectrum, many near UV wavelengths are also absorbed by the materials of the eye.

Luke Campbell

Holger Bjerre points out that while such UV wavelengths do not penetrate the eye, they will abrade the surface of the eye. After all, such UV lasers are used for laser-vision correction surgery. Such abrasion may or may not be correctable, but it is damage.

If I'm not concerned about civilian eye safety and I don't care if the bad guys can see where I am, visible green is probably a pretty good wavelength to use for long distance lasing - it focuses well compared to longer wavelengths but doesn't suffer much from atmospheric Rayleigh scattering like shorter wavelengths.

Luke Campbell

Is there even a plausible solution to the eye safety problem? I can see that for missile defense or blowing up IEDs, eye safety might not be too much of a problem...but for small arms it seems implausible to field weapons that tend to leave civilians blind.

Isaac Kuo

You can cut down on it by a lot by using frequencies that don't pass through the eye. That means either greater than 1400nm (infrared to microwave) or less than 400nm (ultrviolet to x-ray). There is still the possibility of indirect blinding caused by the target of the laser being heated white-hot and emitting thermal radiation, and it's possible to actually produce sunburns on the cornea if enough radiation hits them, but these are lesser problems (and the latter effect probably isn't a factor at ranges where the heat won't also start fires).
For that matter, self-focusing lasers may not reflect well and thus have similar advantages.

Anthony Jackson

Other than repeating what Anthony said, let me just expand a bit on the self focusing aspects. A self focused filament will convert the initially coherent laser radiation into incoherent white light directed by the lens that its field creates in air rather than the inherent directionality of the light. Take away the air, or the high field causing the lensing, and the light will spray out in all directions (it is actually mostly forward and backward propagating, but is not tightly collimated). If part of the light is reflected, it will lose this self focusing ability. Even incoherent light can be dangerous if it is intense enough, but less so than a collimated reflected beam. In addition, when the beam interacts with solid matter, it will flash that matter to plasma, and the plasma will absorb much of the beam. Most reflections will be off the plasma-air interface, which is likely to be irregular thus giving diffuse rather than specular reflection.
All this assumes that the self focusing works as advertised. If your gun tries to self focus the beam half a meter in front of the target, but it misjudges the distance to the target, the beam could still be monochromatic and coherent, and might reflect off shiny bits. Is this more of a worry than bullet ricochets from modern firearms? I don't actually know.

Luke Campbell

This filamenting ability seems to require a very high power level, so diffuse reflection would seem to be dangerous. I'm thinking of close quarters situations, like a hostage rescue, where the civilians in question might be less than a meter from the bad guys you're shooting at.
But let's suppose we're not using filamenting. A "death ray" laser weapon is going to need to be somewhat powerful in order to take down the bad guy. Even if we're using a wavelength that is blocked by the eye, diffuse radiation from the hot target spot might be a problem. Is it?
Or maybe the diffuse radiation is only as much of a threat to eyesight as the muzzle flash of a pistol?

Isaac Kuo

Isaac Kuo: This filamenting ability seems to require a very high power level, so diffuse reflection would seem to be dangerous.
Luke Campbell: While the power can be mind bogglingly high, the total energy can be fairly moderate. To cause eye injury (of the sort normally discussed with lasers) you need to deposit enough energy onto a point on the retina to cause third degree burns, fast enough that heat conduction can't take the energy away. Filamented beams clearly have the fast part down, but an uncollimated reflection may not deposit enough energy to burn (or it might — we really don't have the experience with this yet).
Isaac Kuo: Even if we're using a wavelength that is blocked by the eye, diffuse radiation from the hot target spot might be a problem. Is it?
Luke Campbell: I expect it is more like the threat of the arc of an arc welder. Glancing at the flashes, or watching from a distance is pretty safe, but the welder himself better be wearing protective eyewear.

Luke Campbell

Looking at laser safety , a typical weapons laser will probably take somewhere between a microsecond and a millisecond to drill into a target, split into multiple pulses.
Each pulse will be something like 10J and 10^-9 seconds. That time gives a safe level of 5×10^-7 J/cm² or 5×10^-3J/m². At 1 meter, the reflected light will probably be 0.1 to 0.5J/m², so each pulse will be a hazard out to 5-10 meters.
In addition, we're delivering 1+ kilojoules over maybe a millisecond. That increases our maximum dose to 1×10^-5J/cm², but we're delivering 100+ times as much energy, so this will give a hazard at 10-20 meters. Note that the safe level is 10% of the 50% damage threshold, so the 50% damage distance is 3-6 meters for a 1 kilojoule laser.

Anthony Jackson

Oh! Blink reflex!
If you use a visible laser, like a green laser, then you can maybe flash a weak "safety" pulse to induce endangered civilian eyes to blink before the main weapon pulses.
Put maybe 0.1 seconds between the safety pulse and the main pulse. That's enough time for civilians to blink but not enough time for a bad guy to dodge the "bullet". That's similar to the time delay of a pistol bullet traveling 30m.

Isaac Kuo

It's not like the safety pulse has to be the same wavelength as the main pulse. However, I suspect a better option is to use a wavelength that doesn't penetrate the eye, and then operate at a power level low enough that plasma formation is not a major factor (relying on regular vaporization). This means that the reflected primary beam is not directly dangerous unless it actually hits someone at near full power, and emitted radiation is (a) fairly long wave, and (b) a small minority of the energy release.
Unfortunately, this still requires bringing the surface up to the sublimation temperature of the material. This is not a problem for humans or for soft armors, but refractory ceramics will require temperatures in excess of 3,000K, which will give an emissions peak in the near IR.

Anthony Jackson

Also note that Protocol IV of the 1980 Convention on Certain Conventional Weapons (issued by the United Nations on 13 October 1995) states:

Article 1: It is prohibited to employ laser weapons specifically designed, as their sole combat function or as one of their combat functions, to cause permanent blindness to unenhanced vision, that is to the naked eye or to the eye with corrective eyesight devices. The High Contracting Parties shall not transfer such weapons to any State or non-State entity.
Article 2: In the employment of laser systems, the High Contracting Parties shall take all feasible precautions to avoid the incidence of permanent blindness to unenhanced vision. Such precautions shall include training of their armed forces and other practical measures.
Article 3: Blinding as an incidental or collateral effect of the legitimate military employment of laser systems, including laser systems used against optical equipment, is not covered by the prohibition of this Protocol.
Article 4: For the purpose of this protocol "permanent blindness" means irreversible and uncorrectable loss of vision which is seriously disabling with no prospect of recovery. Serious disability is equivalent to visual acuity of less than 20/200 Snellen measured using both eyes.

Protocol IV of the 1980 Convention on Certain Conventional Weapons

Of course the U.S. Department of Defense is working on the Personnel Halting and Stimulation Response rifle, which is a laser-blinding weapon intended for crowd control. It is intended to skirt the 1995 UN Protocol on Blinding Laser Weapons by not blinding the target permanently (they hope).

THE LIGHT OF DARKNESS

(ed note: Warning: Spoilers for the story follow. The protagonist is a native of the fictional African nation of Umbala, which on the equator has a fictional Zambue crater. The nation has been taken over by a power-mad dictator named Chaka who has instituted a reign of terror. The protagonist is only a humble astronomer, but realizes Chaka must be stopped. The fact that Chaka put to death several of the astronomer's relatives only makes it personal.

The radio telescope will be opening soon. The astronomer knows that Chaka won't be able to resist taking the elevator to the top of the telescope and overlooking his domain.

Meanwhile, the narrator is waiting on the other side of the hills.)

 It seems strange that my country, one of the most backward in the world, should play a central role in the conquest of space. That is an accident of geography, not at all to the liking of the Russians and the Americans. But there is nothing that they could do about it; Umbala lies on the equator, directly beneath the paths of all the planets. And it possesses a unique and priceless natural feature: the extinct volcano known as the Zambue Crater.
When Zambue died, more than a million years ago, the lava retreated step by step, congealing in a series of terraces to form a bowl a mile wide and a thousand feet deep. It had taken the minimum of earth-moving and cable-stringing to convert this into the largest radio telescope on Earth. Because the gigantic reflector is fixed, it scans any given portion of the sky for only a few minutes every twenty-four hours, as the Earth turns on its axis. This was a price the scientists were willing to pay for the ability to receive signals from probes and ships right out to the very limits of the solar system.
Chaka was a problem they had not anticipated. He had come to power when the work was almost completed, and they had had to make the best of him. Luckily, he had a superstitious respect for science, and he needed all the rubles and dollars he could get. The Equatorial Deep Space Facility was safe from his megalomania; indeed, it helped to reinforce it.
The Big Dish had just been completed when I made my first trip up the tower that sprang from its centre. A vertical mast, more than fifteen hundred feet high, it supported the collecting antennas at the focus of the immense bowl. A small elevator, which could carry three men, made a slow ascent to its top.

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As soon as the NASA technicians had installed their equipment and handed over the Hughes Mark X Infrared Communications System, I began to make my plans.

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Colonel Mtanga, his Chief of Security, would object, but his protests would be overruled. Knowing Chaka, one could predict with complete assurance that on the official opening day he would stand here, alone, for many minutes, as he surveyed his empire. His bodyguard would remain in the room below, having already checked it for booby traps. They could do nothing to save him when I struck from three miles away and through the range of hills that lay between the radio telescope and my observatory. I was glad of those hills; though they complicated the problem, they would shield me from all suspicion. Colonel Mtanga was a very intelligent man, but he was not likely to conceive of a gun that could fire around corners. And he would be looking for a gun, even though he could find no bullets….
I went back to the laboratory and started my calculations. It was not long before I discovered my first mistake. Because I had seen the concentrated light of its laser beam punch a hole through solid steel in a thousandth of a second, I had assumed that my Mark X could kill a man. But it is not as simple as that. In some ways, a man is a tougher proposition than a piece of steel. He is mostly water, which has ten times the heat capacity of any metal. A beam of light that will drill a hole through armour plate, or carry a message as far as Pluto—which was the job the Mark X had been designed for—would give a man only a painful but quite superficial burn. About the worst I could do to Chaka, from three miles away, was to drill a hole in the colourful tribal blanket he wore so ostentatiously, to prove that he was still one of the People.
For a while, I almost abandoned the project. But it would not die; instinctively, I knew that the answer was there, if only I could see it. Perhaps I could use my invisible bullets of heat to cut one of the cables guying the tower, so that it would come crashing down when Chaka was at the summit. Calculations showed that this was just possible if the Mark X operated continuously for fifteen seconds. A cable, unlike a man, would not move, so there was no need to stake everything on a single pulse of energy. I could take my time.
But damaging the telescope would have been treason to science, and it was almost a relief when I discovered that this scheme would not work. The mast had so many built-in safety factors that I would have to cut three separate cables to bring it down. This was out of the question; it would require hours of delicate adjustment to set and aim the apparatus for each precision shot. I had to think of something else; and because it takes men a long time to see the obvious, it was not until a week before the official opening of the telescope that I knew how to deal with Chaka, the All-Seeing, the Omnipotent, the Father of his People.

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It took me three days to install the carefully silvered, optically perfect mirror in its hidden alcove (at the top of the hills). The tedious micrometer adjustments to give the exact orientation took so long that I feared I would not be ready in time. But at last the angle was correct, to a fraction of a second of arc. When I aimed the telescope of the Mark X at the secret spot on the mountain, I could see over the hills behind me. The field of view was tiny, but it was sufficient; the target area was only a yard across, and I could sight on any part of it to within an inch.
Along the path I had arranged, light could travel in either direction. Whatever I saw through the viewing telescope (at his observatory on one side of the hills) was automatically in the line of fire of the transmitter.
It was strange, three days later, to sit in the quiet observatory, with the power-packs humming around me, and to watch Chaka move into the field of the telescope (standing at the top of the radio telescope on the other side of the hills). I felt a brief glow of triumph, like an astronomer who has calculated the orbit of a new planet and then finds it in the predicted spot among the stars. The cruel face was in profile when I saw it first, apparently only thirty feet away at the extreme magnification I was using. I waited patiently, in serene confidence, for the moment that I knew must come—the moment when Chaka seemed to be looking directly toward me. Then with my left hand I held the image of an ancient god who must be nameless, and with my right I tripped the capacitor banks that fired the laser, launching my silent, invisible thunderbolt across the mountains.
Yes, it was so much better this way. Chaka deserved to be killed, but death would have turned him into a martyr and strengthened the hold of his regime. What I had visited upon him was worse than death, and would throw his supporters into superstitious terror.
Chaka still lived; but the All-Seeing would see no more. In the space of a few microseconds, I had made him less than the humblest beggar in the streets.
And I had not even hurt him. There is no pain when the delicate film of the retina is fused by the heat of a thousand suns.

From THE LIGHT OF DARKNESS by Arthur C. Clarke (1966)

Disintegrate

WARNING: if you are easily nauseated or upset, I'd skip this section if I were you. Also skip if you are younger than 18, this means You.

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  Video "Star Trek Phaser Effects"
  Vaporization Effects starts at 54 seconds
  click to play video

Among the many settings on the amazing Star Trek Phaser dial-a-gun is "Dematerialize". This is basically a disintegrator ray, where whatever you shoot turns into a glowey outline and quietly fades away.
Rocketwash. It ain't going to be so soft and gentle. Vaporizing a human body will be akin to detonating a mannequin made out of C-4 plastic explosive. Not to mention what happens when the laser battery in the victim's laser pistol cooks off.
Scott Lowther has the straight dope:

SET PHASERS TO “VAPORIZE”

I’ve always liked the phasers of Star Trek more than the blasters/turbolasers of Star Wars. Ship to ship: phasers are computer controlled and seem to always hit the target (even if they don’t necessarily damage the target), while turbolasers are manually targeted and can’t seem to hit a damn thing. Same with hand-held weapons… phasers are zero time of flight weapons that non-professional soldiers can wield accurately, while blasters seem to travel slower than bullets and the biggest, most expensive and advanced military out there has troops so poorly trained that they can’t seem to hit the broad side of a barn.
But there’s one area where blasters are better than phasers: total energy usage per shot. If you get shot with a blaster, it’s like getting shot with a firearm. Perhaps an extra powerful firearm… a 12-gauge filled with buckshot, perhaps, but still roughly equivalent to a conventional gun. But phasers have a top setting that will vaporize a human. That’s not just overkill, that’s an insane level of overkill. It’s like using a TOW anti-tank missile to target an individual.
And this is one of the things that Star Trek got wrong. Not that it’s necessarily impossible for a weapon the size of a keychain to vaporize a human, but that the process of vaporizing the human wouldn’t utterly trash the surroundings. Face it: you’re converting, oh, 180 pounds of water to steam, and converting the calcium in the bones, the metal and plastic in his clothes, tools, weapons, etc. into plasma. And if the target is also holding a phaser, you’re converting that into vapor, which means that its battery (or whatever the power source is) is going to explode.
Phaser-vaporizing someone on board a spaceship is going to be a disaster, because by converting 180 pounds of water into steam, you’re increasing the volume by a factor of around 1,000. Imagine if the room the target was in suddenly found itself loaded with 1,000 more people. The pressure will blow the hull apart. While a blaster will simply poke a hole in the target, maybe burning their clothes.
Star Trek always made the result of someone getting vaporized pretty… well, sterile. Zap, bright light, gone. But it wouldn’t be like that. If you want to know what someone getting phasered at full power would look like, YouTube provides. Behold the phenomenon of the “Arc Flash,” where enough electrical energy can be dumped into a human to convert said human into a steam explosion. Obviously, this might be considered slightly grisly, so gather the kids around (occurs at 1:14; you can adjust settings to .25 speed to watch the guy go from “normal” to “Hey, he’s a glowing blob, just like in Star Trek” to “Where’d he go?” in three frames):

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  WARNING
  Person vaporized by high voltage
  click to play video
  Do NOT click on "YouTube" logo to go to main website, because related video thumbnails along the side are gruesome.

It’s kinda unclear just what the hell happened here, but it sure looks like the guy was converted into mostly a cloud and a bit of a spray. In any event, there’s no missing the fact that something really quite energetic happened to the guy. The captain of the Klingon scout vessel vaporizes one of his crew on the bridge, they’re going to be scrubbing it down for days, assuming that the steam and overpressure doesn’t kill everyone else on the bridge.
In the later Star Trek series, the “vaporize” setting seemed to fall out of fashion. More often than not energy weapons were used as “simple blasters” of roughly firearm-power. And that’s all you need. Firearms are as powerful as they are because that’s Good Enough. You don’t need a weapon that essentially turns the target into a suicide bomber.
It might be interesting to actually show accurate phasering on some future Star Trek movie or episode. In one scene, out heroes board a wrecked space station. They go in a room where someone was shot with a phaser set to Blaster Mode: the doctor rushes over, applies hand to carotid artery, looks up sadly and says “He’s dead.” Then they go to the next room, where someone was vaporized. All the furniture is smashed up against the walls; the floor, ceiling, walls, furniture are all covered in gore. Blood sprayed everywhere, teeth embedded in the ceiling, small bits of burnt, semi-burnt and unburnt eviscera scattered about, bits dripping from the ceiling. Doc stands there in the door, slack jawed; Ensign Redshirt looks in and promptly doubles over and upchucks the Tribble Surprise he had for lunch. Captain Hero looks looks in, turns a shade of green and asks “So, Doc, who was it?”
Doc looks at Captain Hero like he’s a freakin’ mo-ron and replies with something like “How the hell would I know?”

From SET PHASERS TO “VAPORIZE” by Scott Lowther (2016)

Design

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  Ancient digital camcorder (2004)

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  Infrared thermometer

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  Ancient film camcorder

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  Ancient film camcorder

What will the laser pistol look like?

The laser weapon will probably end up looking something like a camcorder, with a big lens that the beam goes through, and a fairly compact design. Since mirrors and internal optics can bend the beam inside the weapon, there is no need for the long barrels you see on modern firearms. Cooling, if necessary, would probably not involve fins - I would expect something more like the radiator on modern automobiles. Remember, shedding your heat through contact with the air is much more efficient than radiation.

(ed note: keeping in mind that using contact with the air doesn't work if there is no air, i.e., in vacuum. C. James Huff notes that there is one kind of fin for radiant cooling and another for air cooling. He mentions that the fins on a CPU hot sink is a good example of the latter. For a vacuum rated laser he recommends a compressed or liquified gas cartridge since a radiant cooler would be inconveniently huge.)

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  Ancient film camcorder

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  Ancient film camcorder

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  Ancient film camcorder

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  Ancient film camcorder

Also, lasers are getting surprisingly efficient. When each beam pulse contains no more energy than imparted to a rifle bullet, lasers might need cooling no more than a modern rifle.

Luke Campbell

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  Artwork by Luke Campbell

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  This is actually a type of camera with a gun handle. DORYUKAMERA Co. 16-millimeter pistol film camera.

Luke Campbell

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  Artwork by Luke Campbell

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  Artwork by Luke Campbell

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  Artwork by Luke Campbell

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  Artwork by Luke Campbell

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  Artwork by Luke Campbell

The aperture is a 6 cm window protecting a 6 cm lens. Below the main lens is a secondary beam path for close focus attacks (close than ~1m). My conception when designing this thing was that the laser was a phase locked semiconductor laser near the butt of the stock, the large opening in the rear is for the cooling fan to force air past the cooling fins of the laser block (the model actually has all the fan blades, but they don't show up in the renders). And just because we all want to be able to "set lasers to stun," there is a pair of alternate beam paths on either side of the secondary beam path that can emit paired self-focused light filaments that will conduct a taser-like current.

Luke Campbell

Battle Laser

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  Battle Laser, artwork by Luke Campbell

...The side vents blow hot air (hot, not red hot)... I was illustrating some equipment from a role-playing setting I've been developing...
These are pulsed lasers of the "blaster" variety, which emit rapid bursts of ultra-short pulses to drill through their targets. They primarily emit in the near infrared at around 1 micron wavelength, but can frequency double their beam color to green if desired. All these lasers are 50% efficient at turning electric energy into beam energy. The beam parameters are fairly flexible — they can emit lower energy beams for a higher sustained rate of fire, for example.
The battle laser is a heavy hitting weapon designed as an infantry longarm to emit high energy beams for light anti-armor and anti-personnel roles, although it is also popular with sportsmen hunting large game. The beam energy is 10 kJ per shot, made up of 50 pulses of 200 J each, spaced 10 microsecond apart. This puts each pulse in the range of a big firecracker. The total beam energy is about the same as a .460 Weatherby magnum bullet — a bullet for the Weatherby elephant gun and the most powerful sporting cartridge in existence.
It can sustain a rate of fire of up to 2 full energy pulses per second, or safely handle overheating by up to 8 full energy shots. It has a mass of 4.5 kg and a 6 cm primary aperture. The beam causes full damage out to about 350 meters. It is commonly powered by a 1.7 kg high capacity power pack, with enough energy for 100 full energy shots and enough power to supply 2 full energy shots per second, although the laser can be hooked to a power backpack via a power cable to allow higher rates of fire and ammunition capacity. 6 cm lens.

(ed note: if my slide rule is not lying to me, 50 pulses at 10 microseconds per pulse will take 0.0005 seconds. 10 kilojoules in 0.0005 seconds is equivalent to 20 megawatts)

The Sniper Laser variant has a larger aperture for accuracy at a greater distance.

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  Battle Laser, artwork by Luke Campbell

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  Sniper Laser, artwork by Luke Campbell

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  Battle Laser 2, artwork by Luke Campbell

Luke Campbell

Assault Laser

The assault laser is designed as a rapid fire anti-personnel infantry weapon. It emits lower energy beams than the battle laser, but has beefed up cooling and power supply systems to allow a greater time averaged power. The beam energy is 4.8 kJ per shot, with a sustained fire rate of 5 full energy beams per second, and can safely handle up to an additional 14 full energy beams worth of overheating. Its mass is 4.5 kg and it has a 6 cm aperture. It has an effective range out to about 250 meters. It is commonly equipped with a 2 kg high capacity power pack, with enough energy for 250 full energy shots and a power sufficient to supply 5 full energy shots per second, although again it can hook into a power cord to attach to a larger power pack for greater ammunition capacity and rate of fire. 6 cm lens.

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  Assault Laser, artwork by Luke Campbell

Luke Campbell

Heavy Laser Pistol

The heavy laser pistol is a bulky handgun for heavy hitting stopping power. The beam energy is 3.2 kJ, with a sustained fire rate of 2 shots per second and a safe overheating reserve of up to 8 shots. It masses 1.25 kg and has a 3 cm aperture. It can keep a tight focus for full beam effect out to about 100 meters. It is commonly powered by a 0.24 kg fast discharge power pack fit into the grip. This can supply the laser with 15 full energy shots and 3 full energy shots per second. Alternately, the laser can be attached to a larger power pack worn on the belt or as a backpack for greater ammunition capacity. 3 cm lens.
(looks like a common civil camera) It's a case of convergent evolution. Both are designed to direct and focus light.

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  Heavy Laser Pistol, artwork by Luke Campbell

Luke Campbell

Medium Laser Pistol

The medium laser pistol is a common self-defense and law enforcement sidearm. It has a beam energy of 1.6 kJ, with a sustained rate of fire of 2 shots per second and a safe overheating reserve of up to 8 shots. The mass is 0.65 kg and it has a 2 cm primary aperture. The effective focus range is around 50 meters. A 0.2 kg fast discharge power pack fits into the grip, which can supply the pistol with 25 shots at up to 5 shots per second. 2 cm lens.
The Auto Laser emits lower energy beams than the medium laser pistol, but has beefed up cooling and power supply systems to allow a greater time averaged power.

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  Medium Laser Pistol, artwork by Luke Campbell

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  AutoLaser, artwork by Luke Campbell

Luke Campbell

Light Laser Pistol

The light laser pistol is a compact sidearm for concealed carry. Its beam energy is 1.2 kJ, consisting of 60 pulses of 20 J each spaced 4 microseconds apart. It has a sustained rate of fire of 2 shots per second and a safe overheating margin of 8 shots. It masses 0.45 kg and has a 1.5 cm primary aperture. The effective focal range is around 30 meters. It is commonly powered by a 0.15 kg power pack in the grip, which gives 25 full power shots at up to 5 per second. 1.5 cm lens.

(ed note: if my slide rule is not lying to me, 60 pulses at 4 microseconds per pulse will take 0.00024 seconds. 1.2 kilojoules in 0.00024 seconds is equivalent to 5 megawatts)

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  Light Laser Pistol, artwork by Luke Campbell

Luke Campbell

Soviet Laser Pistol

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Ah! The infamous Soviet Laser Pistol!
Details are sketchy but apparently it is not a hoax, it was a prototype, it was meant for Soviet cosmonauts to defend themselves, and it didn't work very well. The prototype was created in 1984. The project leader was Professor Major-General Victor Samsonovich Sulakvelidze, assisted by B. N. Duvanov, A. V. Simonov, L. I. Avakyants, and V. V. Gorev. Currently it is on display at the Museum of Military Academy RVSN (the project site), where it is the most popular exhibit. Many of the visitors ask if they can hold it.
The weapon was intended for cosmonauts to ward off attacks from evil American astronauts, and was to have a mass no greater than a conventional army sidearm. It is unclear why they started with a laser. Probably they were either concerned about the recoil from a conventional slugthrower in free-fall, or they wanted to demonstrate the superior technology of Mother Russia. Officially it was a "self-defense" weapon.
Naturally they ran full-tilt into the power supply problem. Apparently they dealt with this by specifying the weapon did not need a beam hot enough to actually cut through the aluminum hull of an evil American spacecraft. It would be acceptable if the weapon was just strong enough to permanently blind American astronauts or burn out American optical sensors. A drastic lowering of the power requirements. This is because both eyeballs and optical sensors obligingly contain lenses which focus the weak diffuse laser beam into a destroying hot spot right where it will do the most damage. However, if the laser bolt was actually strong enough to poke a hole in an American spacesuit, that would be great.
Ostensibly it used the same basic design as the old mark one, mod zero Ruby Laser. A solid rod of lasing medium inside an optical resonator is pumped by intense light. The ruby laser used a flashtube much like a camera strobe to pump the ruby rod. However Soviet laser pistol instead used a magazine full of pyrotechnic flashbulb"bullets". Flashtubes require lots of electrical power, a flashbulb just needs a spark to set it off.
When a bulb was ignited, the intense light would pump the pistol's neodymium-doped yttrium aluminium garnet rod, creating a near infrared laser beam (1064 nm). The two ends of the rod were mirror plated to create the optical resonator. If I a reading the Russian translations properly, there was a later design replacing the garnet rod with fiber optics (30 micron diameter each, 300 to 1000 fibers) doped with neodymium.
The flashbulbs were full of oxygen and zirconium foil/powder, plus a metal salt to tune the emitted light to the best pumping frequency. Each bulb is ignited by an electric spark (from a piezo-electric device in the pistol, attached to a rail under the barrel) passing through a tungsten-rhenium filament coated with a combustible paste. It burns about 5 milliseconds at 4733 Kelvin (4460° C). Burning zirconium emits about three times as much light as burning magnesium. In all likelihood after each shot a bolt action was used to eject the spent bulb and to chamber a fresh one from the magazine. The weapon is not automatic, each new flashbulb much be chambered manually. The flashbulbs are non-toxic and not prone to spontaneously detonate, which was another requirement.
The magazine contained eight flashbulbs, each 10mm in diameter. Each laser bolt contained something between one and ten joules of energy (about the same as a BB gun), and had an effective range of 20 meters. The pistol had a length of 180 millimeters.
The conversion of the Soviet defense industry caused the project to be cancelled. There was some talk about altering it into some sort of medical tool, but nothing ever came of it.

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  Box in foreground is the piezo-electric device that igntes the flashbulb

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  Pistol with magazine and piezo-electric device removed

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  Details of bolt action

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  Weapon "breaks" open to allow access to laser rod

Particle Beam

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  Unlicensed nuclear accelerators from Ghostbusters (1984) Whatever you do, don't cross the streams.

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  Lightning gun from the game QuakeWars

Particle Beam Weapons uses a high-energy beam of atomic or subatomic particles to damage the target by disrupting its atomic and/or molecular structure.

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 Their minor draw-back is the fact that each shot you fired would have the side effect of exposing you to a lethal dose of radiation. At least if you were standing inside an atmosphere when you pulled the trigger. This is because of backscatter and Bremsstrahlung.

But other than that they would be quite spectacular weapons.
You see, in the vacuum of space there is nothing to impede the high-energy beam of particles from expending all their deadly energy on your target. But firing a particle beam through an atmosphere is like sending a load of red-hot buckshot through a room full of dynamite. When you are standing inside the room.
The high-energy particles start ricocheting off air molecules like a radioactive pinball machine. This is called backscatter. Quite a bit of it will reflect back and hit you, the weapon wielder. Not enough to blow a hole in you, but more than enough to give you radiation sickness. This is because a significant part of the backscatter is happening a few centimeters in front of the gun muzzle, which means it is happening one arm-length plus a few centimeters away from your vulnerable pink body. Less if you are firing from the hip.
And then there is Bremsstrahlung. When a charged charged particle (like, say, in a particle beam weapon) is decelerated by another charged particle (like, say, a proton in an air molecule) the lost kinetic energy turns into electromagnetic radiation. At this point medical technicians are blanching as they recognize the mechanism used in an x-ray tube, creating useful but deadly x-rays. Again, a significant part of the Bremsstrahlung occurring one arm-length plus a few centimeters away from your vulnerable pink body.

The problem with particle beams is that scattered radiation from the beam will irradiate the person firing the gun. When you are throwing around kilojoules of ionizing radiation, this will be enough to cause radiation burns, radiation sickness, sterility, and possibly cancer and genetic damage.

Luke Campbell

At kilojoule levels in air the backscatter isn't terribly bad; these would be very high-energy electrons, which tends to collimate the scattered radiation in the forward direction. Particle-beam artillery would be another matter, of course.

Dr. Schilling

Dr. Schilling mentions above that the conventional way to generate particle beams are with pulsed linear induction accelerators, but these will be difficult to reduce to pistol size. A more radical method of creating particle beams is with wake field accelerators, which produce electron beams on the electric fields of forced plasma waves.
He also mentions that high-current electron beams tend to be self-focusing in air, which simplifies things if you take that route. For ranges much over a hundred meters you have to start worrying about energy loss, which can probably be dealt with. For handguns, it isn't a problem.
You'll need a bit over a kilojoule of output energy to reliably incapacitate a human target, just like lasers. Unlike lasers, you won't have to pulse the beam, just pour it on in one big bolt.
Luke Campbell and Anthony Jackson got into a discussion of this. Alas it is over my head like a cirrus cloud.

Semantically, "particle beam" usually means the things being shot out the end can be treated as individual particles, without too much interaction. "Plasma" usually has significant inter-particle interactions.
Practically, particle beams fire a stream of relativistic atoms or sub-atomic particles. These are beams of ionizing radiation — you know, the stuff the anti-nuke crowd gets so worked up about.
If you get a particle beam intense enough to burn someone, it will also deliver a lethal dose of radiation from a hit anywhere on the body while it is at it. Radiation will scatter from the beam "impact" site, irradiating things around it. In an atmosphere, radiation will scatter off air molecules to irradiate things near the beam. Some of it will backscatter, irradiating whatever fires the gun. Forget about a sci-fi hero using a particle beam "blaster" — after blasting a hoard of bug eyed space aliens, he'd be sick or dying from radiation poisoning. In real life, particle beam weapons were considered for their ability to use radiation to disable things (mostly ICBMs) without necessarily blowing holes in them.
Using real tech, there are only two types of particle beams to worry about: electron beams and neutral particle beams. Electron beams are nice because relativistic electrons can get through about half a kilometer to a kilometer of air before either being brought to a stop by collisions with air molecules or (for higher energies) colliding with an air molecule and disintegrating both into an uncollimated shower of radiation. They also exhibit a self focusing effect in air - their interaction with the air concentrates the beam to prevent it from spreading out (this is quite important - since electrons are so much lighter than air molecules, they tend to bounce all over the place if shot out in low quantities - hit a molecules and your electron can end up going in any direction). Note that just because the beam is self focusing, it does not necessarily keep going in the same direction - I've heard humerous stories by observers of atmospheric high power particle beam tests of the beams wandering off in random directions. Some sort of beam guiding mechanism would be necessary (perhaps use one of those self focusing ultrashort laser pulses to ionize a path).
Electron beams don't work at all well in space, since the like charge of the electrons tends to blow the beam apart. Also, the charged electrons tend to interact in wonky ways with the earth's magnetic field, leading to unpredictable beam paths. Hence the neutral particle beams. Here, you accelerate an atom stripped of one or more electrons, and then neutralize the atom before shooting it off into space. Since all the particles are uncharged, they ignore magnetic fields and each other, and just merrily drift along until they slam into their target at relativistic velocities. They are pretty useless in air - the collisions with air molecules either stop the beam within a few meters or disintegrate it into an unfocused shower of radiation.
Plasma guns have a significant problem. If the plasma is at higher pressure than the surrounding air, it expands and pushes the air out of the way, becoming a cloud rather than a beam or pulse. Clouds of lightweight gas (a plasma is essentially a gas with wierd interactions with electric and magentic fields) are quickly stopped by air pressure, and will cool quickly as well. If it is at really high pressure, it will expand violently - this is what we call an explosion. Trying to confine the plasma with electric or magnetic fields just makes things worse. In order to get the fields to travel with the plasma and contain it, they need to be generated by sources within the plasma (generally electric currents generating magnetic fields). The forces exerted by the fields on the sources either helps to explode the plasma (for magnetic fields and electric currents) or squishes the plasma in one direction while helping it to explode in another (for electric fields and macroscopic electric charges).
So, we need to keep the pressure down. Ignoring electric and magnetic fields, we find that the pressure is given by a constant times the temperature times the density. The temperature is necessarily high (there are cold plasmas, but what's the point as a weapon?), so we need low density. Unfortunately, low density means low energy per volume (it turns out that the energy per unit volume is given by the pressure - you can't win by playing with combinations of higher temp and lower density or vice versa). As a result, you need to squirt out a large volume of hot, low density plasma to deliver much energy to your target. You can do this by squirting out a stream of it really fast. You don't have a "pulse" or "beam" of plasma this way, you have a plume (or, equivalently, a jet). You train your jet on your target and hold it there for long enough to burn through. This is sort of a very energy intensive flame thrower with the disadvantage that your target is not covered with sticky, burning chemicals after you take the jet off him (as an idea of how energy intensive, if you can direct the beam only onto the person's skin, about half a megajoule is needed to cause lethal burn injuries involving third degree burns to exposed skin, second degree burns under light clothes, and ignition of hair and clothes. In practice, more energy will be required because the jet will not all impact your target. Compare this to the energy of an assault rifle bullet [500 times less] or an arrow [10,000 times less] for an idea of why plasma guns will not be used - the same energy could propell 500 coilgun projectiles, each highly lethal and much more penetrating).

Luke Campbell

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  High voltage discharge (simulated lightning) - Right: with laser guidance - Left: without laser guidance. Image from Téramobile

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Apparently an electron particle beam would resemble a lightning bolt.

(Jason: "For an idea of an electron beam path... Look at lightning, which If I'm reading right sounds about the same")
Not exactly, but close, unless you have some sort of beamguide. If you create an ionized path with a laser, the electron beam will tend to follow that path.
Actually, that's true of lightning as well. this shows images of an electric discharge done normally and with a beam path created by a femtosecond-terawatt laser.
The shot will basically look like a straight lightning bolt (blue-white flash with extremely short duration), and will produce a snap of sound, though at the power levels proposed it won't be very loud; probably rifle bullet level.
The wound won't be all that visible, but will seem peculiar as compared to a bullet wound, since the skin will not be pushed inwards and may actually be pushed outward. It's possible that the skin will not even be visibly punctured, just blackened in a spot (depends how focused the beam actually is, which is unclear). Any tissue near the impact site will be dead or dying, and nervous system operation will be disrupted (stuff near the beam may absorb 100,000 rads or more).
I'm not sure how well it will penetrate flesh; electrons will go a couple inches in, and secondary X-rays (and, most likely, gamma rays from positron annihilation — very high voltages are required, meaning you get pair production of electrons and positrons) will go a bit forward of that, further penetration is dependent on the ability to open a hole in tissue and/or fully ionize the flesh.

Anthony Jackson

The CSDA (continuous slowing down approximation) range of a 1 GeV electron in skeletal muscle tissue is close to one meter - lower energy electrons will travel less far. This means it is quite possible for the burn path to completely transfix the target. It is also useful to note that the energy deposited per unit length (or volume) is highest near the end of the track when the electrons are moving slower. For a beam that penetrated, say, 10 cm into tissue, this would mean that you could have a narrow burn entrance wound without a visible hole but get significant flash vaporization of tissue inside the victim.
That same 1 GeV electron will travel over 800 meters through dry air at sea level in the CSDA. If you are shooting at distant targets, however, keep in mind that the electrons in the beam will have lower energy the more air they have to punch through, and thus will have lower penetration at the target.
Data is taken from ESTAR

Luke Campbell

We're talking a pistol here. It's probably 10-100 MeV, for a penetration of a couple of inches.

Anthony Jackson

Mr. Andrew Broeker has some issues with Mr. Campbell's approximations:
My first concern regards Luke Campbell's use of the CSDA approximation to calculate electron penetration depth. This approximation should only be used for very thin targets where only a small fraction of incident particles' energy will be lost traveling through the sample. Since the discussion regard's the loss of all energy, more math gets involved. I've done similar calculations in my lab work and would be happy to do so again if Luke could provide me with the ESTAR data he used to do this.
My second concern is Luke's suggestion that weaponized electron beams should be a micron in width. While he is correct that modern accelerators can achieve such narrow beams, they can do so only via collimation. To achieve such beam diameters, up to 99% of your beam ends up getting dumped on your collimators. This has two consequences. First, drastically reduced beam current. Second, the operator gets irradiated far worse than his target.

Andrew J. Broeker

With realistic breakdown voltages around 10 to 20 MV/m, a 10 MeV pistol would be half a meter to a meter long. Given additional engineering considerations, for realistic electron beam pistols I wouldn't expect more than 1 to 2 MeV, maybe 5 MeV at the limit. The ranges in skeletal muscle: 1 MeV - 0.5 cm, 2 MeV - 1 cm, 5 MeV - 2.5 cm. Multiply by 800 for the range in air. Unless you consider non-linear beam-matter interactions (such as heating a tunnel to a partial vacuum) this gives very short ranges in air (4 to 20 m), and you would need to use multiple pulses to blast a deep enough hole to reach vital organs.
If you want better performance out of a pistol sized device for a sci-fi setting, you need to postulate a Sufficiently Clever method to get around the breakdown voltage limit. Once you do this, there's no obvious upper limit on the available electron energy.

Luke Campbell

It's a problem, though I'm not sure how many MeV you really need (my research-fu is failing me). As a practical issue, going above 10 MeV is of limited value for penetrating armor, but may have value for enhancing range.
I found some interesting studies, that were above my head, last time I looked into this. I can't find any of them right now, but I recall a need for a fairly high voltage, a very high current, and a very clean beam, to maximize atmospheric propagation. Key terms might be Nordsieck length and hose instabilities.
Some things I found that seem vaguely promising/related, though they're generally abstracts and often aren't articles I can get at or really understand if I did read them.

Anthony Jackson

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This looks useful. It indicates there are two range-limiting effects.
The first is the loss of energy of the beam electrons due to ionization of the air molecules. The other is the spread of the beam due to collisions of the electrons with air molecules causing random changes in direction to the electrons. Magnetic self pinching allows the beam to recover somewhat from the scattering beam spread, but not entirely.
One necessary value for analyzing electron beam range due to scattering is the Alfven current, denoted I_A. This is the current at which the magnetic self focusing overcompensates and causes some of the beam electrons to turn around and move in the opposite direction.
It is the upper limit on the current of an electron beam (with the caveat that the limit is for the net current - for rapid rise times, magnetic induction can cause plasma electrons to move backwards along the beam, partially canceling the beam current and allowing more beam electrons to pass by before the limit is reached).
For electrons, this limiting current is

I_A = 17E3 amperes * β * γ

where β = velocity / (speed of light) and γ = 1 / sqrt(1 - β²) is the usual relativistic parameter.
The other necessary value is the increase to the spread of the beam due to scattering per unit length traveled, neglecting magnetic self focusing. For dry nitrogen with at atom density (in particles per cubic meter) of N this value is

d(θ²) / dz = 1.04 meters² * N / (γ² * β⁴)

At STP this becomes

d(θ²) / dz = 2.8 / (γ² * β⁴) m^-1

If we neglect energy loss of the electrons, the beam spread can be determined analytically. For a beam of current I and initial radius R_0, the Nordsiek equation gives the spread of the beam with distance

R(z) = R_0 exp[(d(θ²) / dz) * z / (2(I/I_A))] = R_0 exp[ z / z_0]

In other words, we get an exponential increase in beam radius over a characteristic range equal to

z_0 = 2I / (I_A * d(θ²) / dz))

As an example, let us look at a beam of 10 MeV electrons with a current of 5000 amperes in dry nitrogen at STP.

I_A = 34E4 amperes

d(θ²) / dz = 0.007 m^-1

z_0 = 4.2 meters

For the electron energy loss range in dry nitrogen, I get 44 meters from this reference. This indicates that our original assumption of neglecting the energy loss in finding the beam expansion is probably fine for a a multiple of z_0 or two.
One consequence of this is that electron beams in air will tend to have very short pulses of high current to maximize the self focusing in order to cancel collisional spreading. Unfortunately, this can hinder heating an evacuated tunnel through the air, since for very rapid pulses the air atoms will not have time to move out of the way of the electron beam.

Luke Campbell

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  Eminiaran disrupter, Star Trek "A Taste of Armageddon"(1967).

17e3 = 17,000, correct? For relativistic electrons we can probably safely approximate β as 1 and γ as 2 * energy in MeV.
θ is what here? Rate of expansion?
It appears we want a current fairly close to I_A; go up to 50,000 amperes and z_0 is now 42 meters.
I suspect this range will change as ionization occurs, assuming the electron beam energy is adequate to cause substantial ionization.
Let's assume a pulse with an initial diameter of 2mm and a current of 50,000 amperes. That's a peak magnetic field of 5 tesla, which is high but not completely out of the believable range, at least as compared to everything else involved. We have a peak current here of 5e11W, putting us just shy of a terawatt. Now, sustain the pulse for 1 nanosecond, thus depositing 500J in the channel.
The channel has a base cross-section of 3.14e-6 m² and a maximum cross-section of four times that, and a length of 40 meters, so figure total volume is about 4e-4 cubic meters, resulting in heating up about half a gram of matter. 500J / 0.5g = 1 MJ/kg, which is less than the ionization energy of the gas, but is sufficient to heat it up to around 1300K (assuming temperature stabilized) and give an average velocity to the gas of 1400 m/s. It will take about one microsecond for gas to evacuate the channel.
Now, the evacuated channel is maybe 1/4 the density. That will increase the range of electrons by a factor of 4, and also reduces N (and thus d(θ²) / dz) by a factor of 4, which will also increase the nordsieck length. This means the initial 40 meters are only as costly as 10 meters normally, and thus we can tunnel another 30 meters. Rinse and repeat; the theoretical limit is 160 meters.
This, of course, ignores problems with the channel formation: much of the deposited energy may be radiated away rather than turning into thermal movement of molecules, and the shockwave from the initial pulse is going to bounce back as it hits nearby molecules.
Now, lets say our beam hits a human, with a cross section of 5 square millimeters when it hits, and we'll assume a penetration depth of 5 cm², for a total affected volume of 0.25 cubic centimeters, or 2,000J/cm³. Assuming the volume is mostly water, water has a specific heat of 4.18J/cm³, so we flash-heat the water from 37C to 515C. This puts it well above vaporization temperature, and in fact well above its triple point, so it starts to expand, cooling as it does so. In theory, up to 77% of the liquid could turn to vapor; in practice, I suspect the actual amount is somewhat less, due to energy being lost from breaking chemical bonds, secondary X-rays spreading beyond the impact area, and energy loss on contact with nearby flesh.

Interestingly enough, if the cross section reaches 38 square millimeters (about a 7mm wide beam) it will no longer vaporize flesh at all, which means it would produce a charred spot and little other visual effect, though anything in the beam path is dead. Of course, the direct damage may not mean much; 5 cm penetration isn't really enough to kill anything (I'm not sure how the secondary X-rays will be distributed, or what energy level they're at, but the secondary radiation may be quite adequate to disrupt the nervous system). Again, secondary pulses on a microsecond time scale may allow tunneling through matter, as long as the power density of the initial pulse was adequate to cause vaporization.

I suspect this range will change as ionization occurs, assuming the electron beam energy is adequate to cause substantial ionization.

Anthony Jackson

I suspect you are correct. At 10 MeV collisional losses dominate, and if you don't lose energy to ionizing the air molecules the energy loss drops by quite a lot. At higher energies you get radiative losses beginning to dominate, and this will not change with increasing ionization. Note that for a beam burning away an evacuated tunnel for it to travel through, we want to have mainly collisional losses - radiative losses take the form of x-rays which can travel several mm or cm through air and thus do not contribute to heating up the volume of air the beam will travel through.

Luke Campbell

Let's assume a pulse with an initial diameter of 2mm and a current of 50,000 amperes.

Anthony Jackson

I don't see any real reason not to make the beam very narrow, say a micron in width or so. We seem to be able to generate micron width beams with modern accelerators.

Luke Campbell

We have a peak current here of 5e11W, putting us just shy of a terawatt. Now, sustain the pulse for 1 nanosecond, thus depositing 500J in the channel.

Anthony Jackson

Complicating this analysis is that the energy deposited increases as the electron energy decreases. However, the energy loss per unit length is roughly constant from 10 MeV to 1 MeV, so this is probably not too significant in this energy range.

Luke Campbell

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  Particle accelerators often take the form of a hollow tube composed of a series of rings. Pulp sci-fi artsts sometimes used the motif

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Backscatter Protection

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  Semi-portable weapon with backscatter shield from the LENSMAN novel Triplanetary

 In science fiction, some weapons could harm the person firing the weapon.
Particle beam weapons when fired inside an atmosphere can backscatter deadly radiation in all directions, including right back at you.
Any weapon which vaporizes your target is converting your opponent's body into an exploding bomb, which you are standing dangerously close to.
The idea is that it would be handy if your weapon had a build-in shield to protect you.

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A minor problem is bulk and size added to the weapon, think about how awkward it is to carry around an opened umbrella.
A more pressing problem is how do you see where to aim with that blasted shield in the way? A reflex aimsight would be an excellent solution. Failing that, a peep-hole might help, peering through a thick block of leaded quartz or something.

LENSMAN SHIELD

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 Disintegrator Ray: Without the later trappings of safety and convenience. The beams used really do vaporize their targets, with all the attendant thermodynamics, so best wear a shielded suit when firing unless you want your front half to be blackened cajun-style.
Kim Kinnison fires his DeLameters while unarmoured on several occasions, and it's hinted that its ancestor, the Lewiston, can also be fired by an unprotected user. The Semi-portable projectors, on the other hand...

(ed note: with semi-portables the person shooting the weapon shelters behind a large integral metal shield with a built-in force field, which the weapon muzzle sticks out of. In the novels the shield is ostensibly to protect you from hostile weapons fire.)

From TV TROPES: LITERATURE / LENSMAN

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  artwork by Louis S. Glanzman

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  artwork by Louis S. Glanzman

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  artwork by Louis S. Glanzman

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  artwork by Louis S. Glanzman

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  artwork by Ron Turner

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  Italian Gun-shield, circa 1540

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  Gun-shield commissioned by King Henry VIII for his body guards. The weapon proved to be too heavy to aim unless rested on a support. Note grating to aim through. (1544)

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  Rear of King Henry VIII gun-shield. Twisty thing near center is a matchlock

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  Mobile dental x-ray with backscatter shield. It is used to take dental radiographs of the patient's teeth.

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  Primary shielding ensure x-rays are only emitted from aperture. Backscatter shield protect operator from x-rays reflected from patient. The backscatter shield is composed of a leaded polymer.

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  Backscatter shield provides a cone-shaped safe area for the operator (blue cone). Cone is designed to be six feet in diameter at the operator's position.

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  Operator must ensure they stay inside the safe area. Here the operator's legs are in the danger zone.

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  Backscatter shield has a hole in the center (to allow x-rays to expose film in patient's mouth), but the hole is plugged by the internal primary shielding.

Hydramatic Mark 4 Flame gun

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This is an example of 1953 space opera in those days of yore when technobabble was king and scientific accuracy was non-existent.

A. This is the Hydramatic Mark 4 Flame gun, which you see me toting with the space suit above. It was developed by Professor Maklin Devonport of the Interplanetary Research Institute in 1995. The Hyramatic takes its name frmo the fact that it operates on a liquid hydro-ammonal compound, which is contained in a cylinder and fed to the gun via a feed line, which couples onto the gun at (a). Its lethal range in space is 2,000 yards - a useful weapon.
B. This is the Atomatic. It is rather bulkier than the "Hydra" but it has the great advantage of being self-contained. It fires .20-calibre atomic bullets; of course a .20 bullet in the old days would have been just about useless, but these, having atomic heads, produce spectacular results. I once saw a pirate ship (which was attacking transports on the Earth-Mars run) torn completely apart by a burst from one of these atom guns. The burst had penetrated the hull and hit the power plant; the pirates never knew waht hit them!
C. Another type of atomic weapon, but working on the controlled-fission principle, the Radiumatic projects a concentrated radiation beam. Another "brain child" of our brilliant Professor Devonport, it is a much heavier weapon than the previous two, but proportionally more effective.
There is no recoil with this weapon or the flame gun and therefore great accuracy is obtainable.
The Radiumatic, when the front hand grip is removed and the tripod screwed into its place, is converted into an idea weapon for ground use - in positions of defense, for instance.

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         STUNT GUN AND LASER GUN JUMP OVER TO STAR BORG LASER GUN

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