Analysis of Performance of Rail Gun Accelerators Powered by Distributed Energy Stores

It has been established that centimeter sized projectiles weighing several grams can be accelerated by electrical forces to velocities in excess of five kilometers per second in a classical railgun. The technologies required to do this are adequately understood, at least in the case where a single energy store is connected to the breech end of the gun. There are two disadvantages to using a single energy store. It is generally desirable to keep gun current as nearly constant as possible and this is difficult to achieve with a single store without making the store excessively large. Rail resistance also becomes a dominating factor as higher velocities are reached because higher velocities require greater gun lengths and correspondingly larger gun resistances. One way to by-pass these limitations is to distribute energy stores along the length of the gun. Not only does this reduce the average rail resistance by reducing the length of rail that carries current at anytime, but it permits inductive energy to be usefully transferred down the gun rather than allowing it to dissipate resistively in the rails. This paper shows how the performance of such a gun may be simulated, by computing the instantaneous rate of change of current in each energy store and by using these values to obtain projectile acceleration. Two specific rail gun systems are examined, the first being a >scientific railgun> designed to propel a three gram projectile to a speed of 20 kilometers per second, and the second being a >space-launch railgun> to accelerate one metric ton to 7.5 kilometers per second.