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A directed-energy weapon (DEW) is a type of weapon which emits energy in an aimed direction without the means of a projectile. It transfers energy to a target for a desired effect. Some of these weapons are real or practicable; some are science fiction.
Recent studies have shown great progress in advanced laser technology. On July 15th 2007, a rebuilt F-4 Phantom was succesfully destroyed over White Sands Missile Range in New Mexico using a powerful laser beam.[dubious]
The energy is in various forms:
Some of these weapons are known as death rays or rayguns and are usually portrayed as projecting energy at a person or object to kill or destroy.
Some lethal directed-energy weapons are under active research and development, but most examples appear in science fiction (or non-functional toys and film props).
Broadly defined, directed-energy weapons can be categorised according to the type of energy used (sound, radio, light, particles, plasma, etc) and the intended effects on the target (physical damage, interference with senses and guidance, disorientation, disabling machinery, incapacitating people, etc).
This article restricts itself to weapons designed to cause physical damage with electromagnetic or particle beams. For some other weapons see:-
For devices which can be confused with (but are not) directed-energy weapons see:-
For directed-energy weapons in fiction see this article and Raygun.
Tactical considerations & problems
Lasers have five main advantages over conventional weaponry:
Since lasers can theoretically defeat artillery and missile attacks, any group fielding an effective laser system will gain decisive advantages in ground, air and space combat. Under radar control, lasers have shot artillery shells in flight, including mortar rounds. This suggests that a primary application of lasers might be as part of a defensive system.
The main difficulty with currently practical lasers is the high expense and fragility of their mirrors and mirror-pointing systems.
Some believe that mirrors or other countermeasures can reduce the effectiveness of high energy lasers. This has not been demonstrated. Small defects in mirrors absorb energy, and the defects rapidly expand across the surface. Protective mirroring on the outside of a target could easily be made less effective by incidental damage and by dust and dirt on its surface.
Laser beams begin to cause plasma breakdown in the air at energy densities of around a megajoule per square centimeter. This effect, called "blooming", causes the laser to defocus and to lose energy to the atmosphere. It can be more severe if there is fog, smoke, or dust in the air.
There are several ways to stop or reduce blooming:
Evaporated target material shading the target
Another problem with weaponized lasers is that the evaporated material from the surface of the target begins to shade the surface. There are several approaches to this problem:
High power consumption
One major problem with laser weapons (and directed-energy weapons in general) is their high energy requirements. Existing methods of storing, conducting, transforming, and directing energy are inadequate to produce a convenient hand-held weapon. Existing lasers are inefficient and waste much energy as heat, and thus need much power and bulky cooling equipment to avoid damage by overheating. Simple air cooling could leave an impractical amount of time between when the device can be safely activated again. These problems, which severely limit laser weapon practicality at present, might be offset by:
If only #2 is available, part of the energy could be used to cool the device.
This problem of storing and/or supplying electrical energy is offset in chemical lasers by using energy released in a suitable chemical reaction instead. Chemical oxygen iodine laser (hydrogen peroxide with iodine) and deuterium fluoride laser (atomic fluorine reacting with deuterium) are two examples of laser types capable of megawatt-range output of a continuous beam. Storing and transporting the chemical fuel presents its own problems with these lasers, and the problems of cooling and overall inefficiency remain.
This problem could also be lessened if the weapon were mounted either as at defensive position near a power plant, or on board a large, possibly nuclear powered, naval or space ship.
Beam absorbed by obscuration in the air
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 brush aside. This effect adds to blooming and worsens the efficiency of the weapon, by wasting more energy to an atmosphere.
Lack of indirect fire capabilities
Indirect fire, as used in artillery warfare to allow the shelling of a target behind a hill, is not feasible with line-of-sight laser weapons. Possible alternatives are to mount the lasers (or perhaps just reflectors) on airborne or space-based platforms.
EM radiation beam weapons
Lasers are very well known in science fiction as a type of raygun. In the real world, 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 million joules delivered as a laser pulse is roughly the same energy as 200g of high explosive, and has the same basic effect on a target. The primary damage mechanism is mechanical shear, caused by reaction (like a rocket) 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.
There is research on real lasers as non-lethal weapons. See Dazzler.
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.
HERF cannons (high-energy radio-frequency weapons), which work on the same principles as microwave ovens, have also shown potential.
On January 25, 2007 the US Military unveiled a device mountable on a small armored vehicle (hummer). It resembles a planar array. It can make people feel around 130 degrees from around 500 yards away. Full scale production of such a weapon is not expected until at least 2010. It is probably the Active Denial System.
Microwave guns powerful enough to injure humans are possible.
Microwave weapons also have considerable anti-material applications, as they are capable of disabling or destroying unhardened electronics. The components of a microwave weapon - a power source, microwave generator and an antenna - are all readily available, and civilians have successfully built and tested simple devices in this category.
Pulsed Energy Projectile
Pulsed Energy Projectile or PEP systems emit an infrared laser pulse which creates rapidly expanding plasma when meeting 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 to be used as a non-lethal weapon in crowd control.
The Mid-Infrared Advanced Chemical Laser is an experimental U.S. Navy deuterium fluoride laser and was tested against an Air Force satellite in 1997.
THEL (Tactical High Energy Laser) is a weaponized deuterium fluoride laser developed in a joint research project of Israel and the U.S. It is designed to shoot down aircraft and missiles. See also National Missile Defense.
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. Certain types of particle beams have the advantage of being self-focusing in the atmosphere.
Blooming is not limited to lasers, but is also a problem in particle beam weapons. Energy that would otherwise be focused on the target spreads out; the beam becomes less effective.
Plasma weapons fire a beam or 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, not to be confused with plasma stealth. Examples are:
Electric beam in a vacuum
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.
This is not a weapon, but is included here for completeness. There is an imitation shotgun which fires a low-powered laser beam at a target which is covered with reflective 90° corners designed to send the beam back where it came from to be detected by a detector on the gun. This is only for target practice without using up ammunition; it has the disadvantage (for a shotgun user) that the beam travels at the speed of light and in a straight line, without teaching the shooter to allow for the effects of wind deflecting the fired shot and the target moving while the shot travels.
Before modern technology developed, many mythologies described gods or demons using weapons that make lightning, such as Zeus's/Jupiter's thunderbolts, Thor's hammer Mjolnir, and the Hindu god Indra's spear (the vajrā).
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. A Byzantine writer hundreds of years later is suggested to have imagined this 2200-year-old death ray, which is attributed to Archimedes. Some attempts to replicate this feat have had some success (though not the attempt 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.
After the astonishing technological advancement during World War I, many such schemes began to appear credible. Harry Grindell-Matthews tried to sell such a ray to the British Air Ministry after that war. He failed to appear to demonstrate his apparatus, however. It was apparently taken to France but has not resurfaced, leading to various conspiracy theory ideas about what might have happened to it, or who might have developed it later.
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, urban legend made real
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 (Jones 1978).
A shoulder-mounted engine-stopping weapon was a central plot element in episode 303 of BBC espionage drama serial Bugs, in which it was referred to as an "engine killer".
See electromagnetic pulse, which is known for its engine-stopping effect, but is an indirect-energy weapon.
Nikola Tesla (1856 - 1943) was a noted inventor, scientist and electrical engineer. He invented Tesla coils, transformers, alternating current electrical generators and was a major early pioneer of radio technology.
He was also noted for making some outlandish claims, among them that he had developed what he called a "teleforce" weapon, or death ray. This death ray would "send concentrated beams of particles through the free air, of such tremendous energy that they will bring down a fleet of 10,000 enemy airplanes at a distance of 250 miles from a defending nation's border and will cause armies of millions to drop dead in their tracks", as said in an article at the time. He offered this invention to the U.S. War Department and to several European countries without success. Various conspiracy theories persist regarding the nature of this device and the whereabouts of Tesla's model or schematics for it.
For the first time in science fiction, H. G. Wells, in his The War of the Worlds novel, described a "death ray"-like laser, in the form of the Martians' "Heat-Ray," which used a heat beam with many properties of the modern laser as a weapon. The weapon used a parabolic mirror to focus and direct a beam of pure heat that had many of the properties of light—this ultimately made 'death ray' like weapons popular in science fiction, which may have stimulated interest in developing real-life directed-energy weapons.
In the later phases of WW 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 sonic weaponry, using parabolic reflectors to project sound waves of destructive force.
This Nazi research included searching in India in the hope that some of the powerful weapons and flying craft described in the Mahabharata and other old Indian books were the real products of supposed ancient technology, rather than mythology based on lightning and other destructive natural forces.
In the 1980s, Ronald Reagan proposed his Strategic Defense Initiative program, which was immediately nicknamed "Star Wars". It suggested that lasers, perhaps including space-based X-ray lasers, could destroy ICBMs in flight. Due to political opposition, this plan was never carried out. For a clearer explanation of SDI, see Strategic Defense Initiative.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Directed-energy_weapon". A list of authors is available in Wikipedia.|