High Quality Content by WIKIPEDIA articles! A railgun is an entirely electrical gun that accelerates a conductive projectile along a pair of metal rails using the same principles as the homopolar motor. Railguns use two sliding or rolling contacts that permit a large electric current to pass through the projectile. This current interacts with the strong magnetic fields generated by the rails and this accelerates the projectile. Particular characteristics are the lack of propellant (only the projectile and the electrical energy to launch it are required to be expended) and the ability to launch projectiles much faster than firearms-based technology allows.