Coilgun
From Free net encyclopedia
A coilgun (also known as Gauss gun, Gauss cannon or Gauss rifle) is a type of cannon that uses a series of electromagnets to accelerate a magnetic shell to very high velocities. The appellation "Gauss gun" comes from Carl Friedrich Gauss, who formulated mathematical descriptions of the electromagnetic effect used by coilguns.
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Overview
Coilguns are often mistakenly called railguns by many sources, and while they are similar in general concept (that is, a magnetic gun), they differ in operation, as a railgun accelerates projectiles down two parallel conducting rails. Coilguns are essentially identical to mass drivers, though on a smaller scale. Kristian Birkeland is commonly considered the inventor of the electromagnetic coilgun, for which he obtained a patent in 1900. The attempts to turn his invention into a usable weapon failed, and the idea was more or less forgotten for many years.
Many hobbyists use low-cost rudimentary designs to experiment with coilguns. One such design would incorporate the use of photoflash capacitors from a disposable camera as the energy source, and a low inductance coil to propel the projectile forward.
Construction
A coilgun, as the name implies, consists of a coil of wire or solenoid with a ferromagnetic projectile placed at one of its ends. A large current is pulsed through the coil and a strong magnetic field forms, pulling the projectile to the center of the coil. When the projectile nears this point, the coil is switched off and a next coil can be switched on, progressively accelerating the projectile down successive stages. In common coilgun designs, the "barrel" of the gun is made up of a track that the shell rides on, with the driver coils around the track. Power is supplied to the magnets from some sort of fast discharge storage device, typically a battery of high-capacity high voltage capacitors designed for fast energy discharge.
Operation
The power must be delivered to each successive electromagnet with precise timing, due to hysteresis. Electromagnets take some time to reach full strength after voltage is applied, so the power supply must start before the shell has reached a particular magnet. The same is true after the power is turned off, and if the shell is on the "far side" of the magnet at that time, the magnet will continue to pull on it, slowing it down. One obvious solution would be to trigger the magnets long before the shell reaches them, but because magnetic force drops off with the square of distance (that is, very quickly) too much power would be lost with such a solution. For this reason most coilguns that use more than one magnet include some sort of electronic timing device for powering the magnets, one that can be adjusted for various parameters such as power of the shot, and the mass of the shell. The gun starts with all of the magnets turned on, and then turns them off one by one before the shell reaches them. One advantage of the coilgun over the railgun is that it can be made arbitrarily long. This has a number of side effects, but the main one is that the acceleration can be much slower over a longer length, meaning that the power needed in any one section of a coilgun is much lower. However this advantage is offset by the cost and complexity of the switching system needed to supply a longer gun.
Superconducting version
A superconducting version of the coilgun is called the quench gun. Resistors attached to superconductive coils waste energy in the coil, which is turned into heat. After a time this heats the superconductor up to the point where it is no longer a superconductor, thereby changes its state to normal (non-superconducting). When this happens the resistance of the coil as a whole suddenly increases, dumping all of the power as heat at a very rapid rate. By carefully controlling the heating rates, the magnets can be "turned off" in sequence at the proper rates to make a coilgun, one that generates very powerful magnetic fields with high efficiency, and tends to have lower hysteresis due to the rapid dissipation of the energy in the coil.
Potential uses
Like railguns and ram accelerators, coilguns have been proposed for use in delivering payloads to space.
As a weapon, the coilgun's advantages include the fact that it has no moving parts, apart from the projectile, and the fact that the only noise heard is the movement of the projectile when it reaches very high speeds. Though coilguns have been shown to reach supersonic speeds, they are far less capable than railguns.
The University of Texas at Austin Center for Electromechanics has been working on this [1] for years for the United States Department of Defense.
Coilguns in science fiction
Coilguns are a popular device in science fiction, especially sci-fi role playing and video games, where they go under such names as Gauss cannon or Gauss rifle (e.g., in Battletech, Syndicate, Fallout, Crimsonland, StarCraft). In the miniature combat game Battletech, the Gauss Rifle is a heavy projectile weapon mounted to some types of Battlemechs. The weapon creates devastating damage at ranges up to a kilometer and produces very little heat, with heat build up being a primary concern to the efficient operation of the Mech, being one of the most powerful weapons in the game (its only downfall is small amounts of ammo and massive weight). It is also featured on games like MechCommander and MechCommander 2.
- In Wing Commander, the coil gun (called a "Mass Driver" in the game, even though the term mass driver implies a much larger object) is used as a primary weapon in some fighter spaceships. However, the medium range/medium damage mass driver is seldom used in later games due to the development during wartime of long-range weapons with strong firepower.
- Metal Gear REX's primary offensive weapon (the rest are defensive) in the video game Metal Gear Solid is identified as a railgun, but the description of its functionality would make it a coilgun. It is intended to launch an uninterceptable, untraceable nuclear weapon (as the coilgun would leave no propellant trail or engine flares, unlike an ICBM).
- In Metal Gear Solid 2, the character Fortune is armed with an experimental rifle incorrectly identified as a railgun, though its abilities and description infer that it is a coilgun.
- EVE Online the railgun turrets class are actually coilguns, a few named turrets in this class do use terms like coilgun and gauss cannon however.
- The Necrons from Warhammer 40,000 use weapons called gauss flayers to tear their targets apart at the atomic level, eating through flesh, bone and armour with ease. These weapons are not coilguns, however, more so an atomic flayer. The name is misleading.
- Fallout 2 has both a Gauss rifle and a Gauss pistol as usable weapons. They are the strongest single shot, non-energy weapons in the game.
- Half-Life has a usable experimental Gauss gun, or Tau cannon. This also appears in Half-Life 2, mounted on a drivable dune buggy.
- Halo 2 introduces a variant of the M12 LRV Warthog (the M12G1 LAAV) with a Gauss rifle mounted on the back, as well as the space based MAC gun (Magnetic Accelerator Cannon) seen firing in the beginning stages of the game.
- StarCraft's Terran Marines each have an automatic C-14 "Impaler" Gauss rifle as their standard weapon.
- PlanetSide has a weapon named Gauss rifle, which is considered a Medium Assault weapon.
- Liero has a weapon named Gauss rifle and shoots a big round object at a high speed.
- Master of Orion features a Gauss autocannon which would quickly fire off multiple shots.
- Mechwarrior 2 contains a Gauss cannon which fires off a magnetic slug.It is highly damaging but has a slow rate of fire.
- X-COM: Terror from the Deep has several forms of Gauss weaponry the player can research, produce, equip, or sell. These weapons accelerate plasma bolts through Gauss fields and aren't real coilguns.
- Descent II has a weapon called a Gauss cannon. It uses the same ammo as the Vulcan cannon but does more damage.
- In Andromeda, many species use Gauss guns since the knowledge on how to create energy weapons has disappeared.
- In the Internet game Ogame, the Gauss Cannon is one of the eight planetary defense structures that can be built.
- In Peter F. Hamilton's Night's Dawn universe, Kulu Embassy troops use a 'gaussgun' to fire projectiles at extremely high muzzle velocities and fire rates.
- The Traveller table-top games feature a handful of man-portable and crew-serviced coilguns bearing the 'gauss' name.
- In the follow-up to the manga Battle Angel Alita, Battle Angel Alita: Last Order, the character Sechs uses a Solenoid Quench gun.
- Syndicate has Gauss gun as the most powerful weapon in the game.