Abstract

In this paper the mechanical efficiency of the railgun is defined as the force accelerating the armature‐projectile combination divided by the total electrodynamic force generated in the gun. The energy expended in a shot may then be equated to the ohmic loss plus the kinetic energy that would have been developed in the absence of mechanical losses. In this way it can be shown that the overall energy efficiency can never be greater than the square of the mechanical efficiency. Comparing calculations with experimental data makes it clear the reported disappointing performance of railguns is due to some ill‐understood mechanical deficiency. A simple experiment is described which reveals buckling and distortion of the rails by recoil action. This explains the mechanical inefficiency. In relativistic electromagnetism, the recoil force should act ‘‘on the magnetic field’’ and absorb field‐energy momentum. The Ampère–Neumann electrodynamics, on the other hand, requires the recoil forces to reside in the railheads and push the rails back toward the gun breech. Experiment confirmed the latter mechanism.