Origin, location, magnitude and consequences of recoil in the plasma armature railgun

Some mention is given of the poor performance of the plasma armature railgun, and the controversial question about its recoil location and origin. Essentials of the very simplest, two-dimensional theoretical railgun model are derived, with emphasis on its pertaining to the moving plasma frame. The necessary Lorentz transformation to the static rail frame is discussed, including its purely relativistic buildup of rail surface charge. This charge is proved to interact with the rail metal ion lattice in the rail electron current regions so as to provide, locally and globally, recoil acting on the rails, in agreement with observations. The main reason for poor railgun performance is attributed to lack of penetration depth into the rails for the recoil forces, resulting in rail surface damage rather than projectile acceleration. Two remedies are suggested: Hall conducting graphite rails or composite rails made of metal and ceramic