Railgun

A Railgun is a type of artillery that fires projectiles at supersonic speeds by launching them using electromagnetism instead of gunpowder or some other chemical propellant. Current expectations for railguns are a 400-mile (643.6 kilometer) range and an impact velocity in excess of Mach 8.

Design

Railguns are specifically weapons that consist of two conductive rails (often made of copper) and a conductive projectile which is inserted between the rails. A current is passed up through the negative rail, across the projectile and then down the positive rail, completing the circuit at the power supply. In some cases, the projectile itself is the sole conductor, while in other cases, a sabot us used to carry the (usually non-conductive) main projectile. Alternatively, a plasma armature can be used--in this setup, thin metal foil is wrapped around a non-conductive projectile. When power is run through the rails and foil, the foil vaporizes into plasma, which caries the needed current. The flow of electricity causes the railgun to behave like an electromagnet, and the Lorentz force causes the projectile to be launched down the rail. This process is specific to the functioning of the railgun, thereby giving the weapon its name. The power requirements of a rail gun are enormous. Significant power generation capability must be connected to capacitors so that the needed jolt of energy can be released. For larger rail guns, such as the military hopes to use, millions of amps are required to produce a sufficient electromagnetic force.

The Railgun should not be confused with the coilgun, also known as the Gauss gun, a weapon which works by generating an electromagnetic field using coils external to the barrel, and using a projectile that is contactless with the firing mechanism (the coils).

Purpose

Photograph taken from a high-speed video camera during a record-setting firing of an electromagnetic railgun (EMRG) at Naval Surface Warfare Center, Dahlgren, Va., on January 31, 2008, firing at 10.64MJ (megajoules) with a muzzle velocity of 2520 meters per second. At this speed, the test projectile actually burns, causing the wave of fire behind it.

Railguns provide a capability for sustained, offensive power projection, complementary to missiles and tactical aircraft. They may be a cost-effective solution to the Marine Corp Naval Surface Fire Support requirements because of their unique capability to simultaneously satisfy three key war-fighting objectives:

1. Extremely long ranges
2. Short time-of-flight
3. High lethality (energy-on-target)

The projectiles them selves can offer several benefits as well. Although the rail gun projectiles are not cheap, they are much less expensive than current weapon systems. Also, they are much smaller, meaning that a navy ship can carry a much greater compliment of weapons than is currently possible.

Progress

The U.S. Navy tested a railgun that shot a 7-pound projectile traveling seven times the speed of sound (mach 7), sending a visible shockwave through the air. They are now up to 23 pound projectiles, which can travel for over 100 miles, and still posses enough kinetic energy to cause significant damage. Developers are also working on including guidance systems and warheads in the railgun rounds.

Current problems with railguns are power generation and barrel life. Railguns require large amounts of power to work in the first place. They also go through barrels quickly because of the extreme temperatures inside the barrel, and intense forces driving the rails apart when used. Components have the tenancy to melt and wear our quickly. However, railguns are being developed successfully by U.S. companies such as General Atomics and BAE Systems. Cool down, fire rate, fire speed, range, and projectile type are all elements in development, but offering all of these along with a durable rail system can be quite complicated. Much work is being done to design a reliable device for the navy which satisfies theses and other requirements. However, limited "hobby" models can be designed by almost anyone with enough knowledge in electrical engineering.