Rail heating analysis for multishot EM gun operation

This paper describes a method of analyzing potential railgun concepts for their rail heating effects in multishot mode. The method is meant to provide a quick estimate of heating effects based on the geometry of the rails and containment and the performance specifications of each shot. First, a coupled electrical-mechanical simulation is run for the railgun in which the effects of current diffusion are included to calculate the effective rail resistance and associated heating as a function of axial position and time. This analysis is then expanded with an assumed current distribution (relative amount of current on top and back of rail compared with the front) to develop a first order temperature distribution in the rail cross section at any specified axial location. This axial section is then subjected to two-dimensional finite element analysis (FEA) to determine the heat redistribution between shots. A sample set of calculations is compared with a single shot experiment incorporating temperature probes in the rails. Finally, the utility of the method for multishot analysis is shown with two simulations, one with and one without active cooling in the rails.