Distributed-current-feed and distributed-energy-store railguns

Abstract

Distributed-type railguns are combinations of power supplies and railguns designed to maintain a nearly constant current in the armature of a railgun and to overcome the accelerator length limitations of simple breech-fed railguns. This limitation arises from the increasing resistance and inductance of the rails with increasing railgun length. The energy efficiency of a railgun system from the primary energy store to the kinetic energy of the projectile can be improved as compared to the simple railgun in some applications. This is accomplished by a reduction of the stored magnetic field energy in the bore of the railgun at the end of a shot and reduction of the resistive losses in the rails. The improved system performance of the distributed railguns over the simple breech-fed railguns is achieved at the expense of greater system complexity. The only distributed-type railguns that have been built to date are distributed-energy-store (DES) railguns. These systems presently use capacitors as the primary energy store, which allows the use of closing switches to initiate current from each of the stores. In this paper a new type of railgun, the distributed-current-feed (DCF) railgun, is presented. The DCF railgun system is a compromise in system complexity and efficiency between the DES railguns and the simple breech-fed railguns. Also, the DCF railgun utilizes closing switches in such a manner as to allow the use of a variety of primary power supplies, including homopolar generators (HPGs), for such electromagnetic propulsion tasks as space launches.