A railgun fires with magnetism and millions of amps, no gunpowder
A railgun has no powder charge and usually no explosive warhead. Instead a surge of current, on the order of a million amperes, races down one metal rail, through a sliding projectile and back along the other. The magnetic force this creates hurls the projectile faster than any chemical gun can easily manage.
Explosive-driven military guns struggle to push shells much beyond about 2 kilometres per second, roughly Mach 5.9. Railguns can readily top 3 kilometres per second. Since a projectile's destructive energy grows with the square of its speed, a fast inert slug can hit as hard as a slower explosive shell. Typical military designs aim for 2,000 to 3,500 metres per second and 5 to 50 megajoules of energy; 50 megajoules is roughly a 5-tonne school bus moving at 509 kilometres per hour.
The simplest version is basically a single loop of circuit, with the sliding piece, called the armature, completing it. That demands enormous current, so a power supply might deliver 5 million amperes for a few milliseconds, generating fields around 10 tesla. Augmented railguns route the current through extra parallel conductors to strengthen the field and reduce the current needed, and some add powerful neodymium magnets. Armatures can be solid metal, a pushing arc of plasma or a hybrid of the two, fed by capacitor banks or pulsed generators.
The idea is older than most people assume. The French inventor André Fauchon-Villeplée built a small working model in 1917 with help from a battery company. After officials watched it, France's armaments ministry commissioned a 30 to 50 millimetre electric cannon on 25 July 1918, but the project died when the war ended that November. His American patent, filed in 1919, was granted in 1922 for an electric apparatus for propelling projectiles.
The appeal for navies goes beyond range. Projectiles are cheap, and a ship carrying no propellant or explosive shells has less to blow up if hit. The obstacle is the power plant, which must deliver catapult-scale energy in milliseconds instead of seconds while staying compact, reliable and survivable in combat.
Source: Railgun
