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A directed-energy weapon (DEW) emits energy in an aimed direction without the means of a projectile. It transfers energy to a target for a desired effect. Intended effects may be non-lethal or lethal. Some such weapons are real, or are under active research and development.
The energy can come in various forms:
Flamethrowers do not fall into this category, as they are actually projectile weapons, the projectile (gas or liquid) is simply on fire.
In science fiction, these weapons are sometimes known as death rays or rayguns and are usually portrayed as projecting energy at a person or object to kill or destroy. Many modern examples of science fiction have more specific names for directed energy weapons, due to research advances.
Laser weapons could have several main advantages over conventional weaponry:
Modern ballistic weapons commonly feature systems to counter many undesirable side-effects mentioned for them in the above comparison. As such it follows that laser weapons' advantage over ballistics could end up more about elegance and cost.
Laser beams begin to cause plasma breakdown in the air at energy densities of around a megajoule per cubic centimeter. This effect, called "blooming," causes the laser to defocus and disperse energy into the atmosphere. Blooming can be more severe if there is fog, smoke, or dust in the air.
Another problem with weaponized lasers is that the evaporated material from the target's surface begins to shade. There are several approaches to this problem:
One major problem with laser weapons (and directed-energy weapons in general) is their high electric energy requirements. Existing methods of storing, conducting, transforming, and directing energy are inadequate to produce a convenient hand-held weapon. Existing lasers waste much energy as heat, requiring still-bulky cooling equipment to avoid overheating damage. Air cooling could yield an unacceptable delay between shots. These problems, which severely limit laser weapon practicality at present, might be offset by:
Chemical lasers use energy from a suitable chemical reaction instead. Chemical oxygen iodine laser (hydrogen peroxide with iodine) and deuterium fluoride laser (atomic fluorine reacting with deuterium) are two laser types capable of megawatt-range continuous beam output. Managing chemical fuel presents other problems, so the problems of cooling and overall inefficiency remain.
This problem could also be lessened if the weapon were mounted either at a defensive position near a power plant, or on board a large, possibly nuclear powered, water-going ship. A ship would have the advantage of water for cooling.
A laser beam or particle beam passing through air can be absorbed or scattered by rain, snow, dust, fog, smoke, or similar visual obstructions that a bullet would easily penetrate. This effect adds to blooming problems and makes the dissipation of energy into the atmosphere worse.
The wasted energy can disrupt cloud development since the impact wave creates a "tunneling effect". Engineers from MIT and the U.S. Army are looking into using this effect for precipitation management.
Indirect fire, as used in artillery warfare, can reach a target behind a hill, but is not feasible with line-of-sight DEWs. Possible alternatives are to mount the lasers (or perhaps just reflectors) on airborne or space-based platforms.
Lasers are often used for sighting, ranging and targeting for guns; but the laser beam is not the source of the weapon's firepower.
Laser weapons usually generate brief high-energy pulses. A one megajoule laser pulse delivers roughly the same energy as 200 grams of high explosive, and has the same basic effect on a target. The primary damage mechanism is mechanical shear, caused by reaction when the surface of the target is explosively evaporated.
Most existing weaponized lasers are gas dynamic lasers. Fuel, or a powerful turbine, pushes the lasing media through a circuit or series of orifices. The high-pressures and heating cause the medium to form a plasma and lase. A major difficulty with these systems is preserving the high-precision mirrors and windows of the laser resonating cavity. Most systems use a low-powered "oscillator" laser to generate a coherent wave, and then amplify it. Some experimental laser amplifiers do not use windows or mirrors, but have open orifices, which cannot be destroyed by high energies.
An electrolaser lets blooming occur, and then sends a powerful electric current down the conducting ionized track of plasma so formed, somewhat like lightning. It functions as a giant high energy long-distance version of the Taser or stun gun.
On January 25, 2007 the US Army unveiled a device mountable on a small armored vehicle (Humvee). It resembles a planar array. It can make people feel as if the skin temperature is around 130 °F (54 °C) from around 500 yards (460 m) away. Full scale production of such a weapon was not expected until at least 2010. It is probably most usefully deployed as an Active Denial System.
Microwave guns powerful enough to injure humans are possible:
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.
When used against humans electromagnetic radiation weapons can have dramatic effects, such as the intense burning sensation caused by Raytheon's Active Denial system, or more subtle effects such as the creation—at a distance—of a sense of anxiety or dread, intense drowsiness, or confusion in an individual or a group of people. Three military advantages of such weapons are:
Potential military(/law enforcement) uses for such weapons include:
A maser is a device that produces coherent electromagnetic waves through amplification by stimulated emission. Historically, “maser” derives from the original, upper-case acronym MASER, which stands for "Microwave Amplification by Stimulated Emission of Radiation". The lower-case usage arose from technological development having rendered the original denotation imprecise, because contemporary masers emit EM waves (microwave and radio frequencies) across a broader band of the electromagnetic spectrum; thus, the physicist Charles H. Townes’s suggested usage of “molecular” replacing “microwave”, for contemporary linguistic accuracy. In 1957, when the optical coherent oscillator was first developed, it was denominated optical maser, but usually called laser (Light Amplification by Stimulated Emission of Radiation), the acronym Gordon Gould established in 1957.
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. 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:
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.
In a vacuum (e.g. in space), an electric discharge can travel a potentially unlimited distance at a velocity slightly slower than the speed of light. This is because there is no significant electric resistance to the flow of electric current in a vacuum. This would make such devices useful to destroy the electrical and electronic parts of satellites and spacecraft. However, in a vacuum the electric current cannot ride a laser beam, and some other means must be used to keep the electron beam on track and to prevent it from dispersing: see particle beam.
The speed of the energy weapon is determined by the density of the beam. If it is very dense then it is very powerful, but a particle beam moves much slower than the speed of light. Its speed is determined by mass, power, density, or particle/energy density.
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.
According to legend, the concept of the "burning mirror" or death ray began with Archimedes who 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. 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 (though not on any of three attempts by the MythBusters television program). In particular, an experiment by students at MIT showed that a mirror-based weapon was at least possible, if not necessarily practical.
In 1935 the British Air Ministry asked Robert Watson-Watt of the Radio Research Station whether a "death ray" was possible. He and colleague Arnold Wilkins quickly concluded that it was not feasible, but as a consequence suggested using radio for the detection of aircraft and this started the development of radar in Britain. See: History of radar#Robert Watson-Watt.
Engine-stopping rays are a variant that occurs in fiction and myth. Such stories were circulating in Britain around 1938. The tales varied but in general terms told of tourists whose car engine suddenly died and were then 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. A possible origin of some of these stories arises 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. A distorted retelling of the events might give rise to the idea that a transmission killed the engine.
Modern car engines are not mechanically, but electronically controlled. Disabling the electronics can indeed stop the engine. This has been implemented in OnStar, which has a remote control feature, but this is not a weapon. It is an add-on to the electronics of the car. Because a car is operating on a closed system, it would be impossible to use an electronic means of disengaging an engine, short of electrocuting it via laser or pulse weaponry. See also electromagnetic pulse (EMP), which is known for its engine-stopping effect, but is an undirected energy weapon.
Nikola Tesla (1856–1943), a noted inventor, scientist and electrical engineer, developed early high frequency technologies. Tesla worked on plans for a directed-energy weapon from the early 1900s until his death. In 1937, Tesla composed a treatise entitled The Art of Projecting Concentrated Non-dispersive Energy through the Natural Media concerning charged particle beams.
During the early 1940s Axis engineers developed a sonic cannon that could literally shake a person apart from the inside. A methane gas combustion chamber leading to two parabolic dishes pulse-detonated at roughly 44hz. This infrasound, 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 compensable 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.[History Channel 1]
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.
The Third Reich further developed sonic weaponry, using parabolic reflectors to project sound waves of destructive force. Microwave Weapons were investigated together with the Japanese.
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. 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 of 2010. Funding has been cut to both of the programs.
During the Iraq War, electromagnetic weapons, including high power microwaves were used by the U.S. military to disrupt and destroy the Iraqi electronic systems and may have been used for crowd control. Types and magnitudes of exposure to electromagnetic fields are unknown.
The Soviets 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 is claimed that Russia made use of the lasers at the Terra-3 site to target the Space Shuttle Challenger in 1984. At the time, the Soviets 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." 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.
Dazzlers are devices used for temporarily blinding or stunning an attacker, or to stop a driver in a moving vehicle. Targets can also include mechanical sensors or aircraft. 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.
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 neurophysiological 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:
Interference with breathing poses the most significant, potentially lethal results.