An artist's conception of a U.S. Navy aircraft carrier equipped with a rail gun. Photo courtesy ONR

Rail guns are of particular interest to the military, as an alternative to current large artillery. Rail gun ammunition, in the form of small tungsten missiles, would be relatively light, easy to transport and easy to handle. And because of their high velocities, rail gun missiles would be less susceptible to bullet drop and wind shift than current artillery shells. Course correction would be important, but all missiles fired from rail gun artillery would be guided by satellite.

It would be more difficult to engineer small arm rail guns, mainly because of recoil. Recoil, the backward action of a firearm upon discharge, is determined by the momentum of the escaping projectile. Multiplying a projectile's mass by its velocity yields its momentum, which for high-velocity rail gun projectiles would be considerable. A portable rail gun that fires very small bullets may be the solution. A small bullet would limit recoil but still carry enough kinetic energy to inflict serious damage.



Rail guns have also been proposed as important components of the Strategic Defense Initiative, popularly known as Star Wars. Star Wars is a U.S. government program responsible for the research and development of a space-based system to defend the nation from attack by strategic ballistic missiles. Rail guns could fire projectiles to intercept the incoming missiles. Some scientists argue that rail guns could also protect Earth from rogue asteroids, by firing high-velocity projectiles from orbit. Upon impact, the projectiles would either destroy the incoming asteroid or change its trajectory.

Rail guns have some interesting non-military applications as well. For one thing, they could potentially launch satellites or space shuttles into the upper atmosphere, where auxiliary rockets would kick in. On bodies without an atmosphere, such as the moon, rail guns could deliver projectiles to space without chemical propellant, which requires air to function.

" " An artist`s concept of the interception and destruction of nuclear-armed re-entry vehicles by a space-based rail gun. Photo courtesy Department of Defense Visual Information Center

Rail guns could also be used to initiate fusion reactions. Fusion occurs when two small atomic nuclei combine together to form a larger nucleus, a process that releases large amounts of energy. Atomic nuclei must be traveling at enormous velocities for this to happen. On the earth, some scientists propose using rail guns to fire pellets of fusible material at each other. The impact of the high-velocity pellets would create immense temperatures and pressures, enabling fusion to occur.

Many of these applications remain in the realm of theory, experimentation and development. Current rail guns do not generate sufficient energies to enable nuclear fusion to occur, for example. And it will likely be 2015 before an all-electric battleship uses a rail gun to launch projectiles at an enemy.

Still, the technology is promising. In 2003, the British Ministry of Defense hosted a one-eighth-scale test of an electromagnetic rail gun that achieved a muzzle velocity of Mach 6, or approximately 2,040 meters per second.

With continued successes such as these, the rail gun may one day be the weapon of choice on the battlefield and the propellant of choice on the launch pad.

For lots more information on rail guns and related topics, check out the links below.

The Science in Fiction If rail guns seem tantalizingly familiar, it's because weapons based on similar principles have been featured prominently in popular culture. In Robert Heinlein's The Moon is a Harsh Mistress, lunar colonists, in a struggle for independence use an electromagnetic launcher to fire iron containers filled with rocks at Earth. In the movie "Eraser," Arnold Schwarzenegger stars as a Witness Protection agent who has stumbled on a secret government plot to sell rail guns to terrorists. And in "Battlestar Galactica," the museum-era warship is armed with rail guns that use both electromagnetic and conventional technologies. These fanciful weapons have also found their way into video games. Rail guns are featured in "Quake", "Metal Gear Solid" and "Red Faction."

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