Analysis on efficiency improvement with a distributed energy store railgun

A distributed energy store (DES) railgun concept was first proposed by Marshall, which excels at higher efficiency, in comparison with a breech-fed one. And it had been testified to lessen the energy remaining in the rails and lower the rails' resistive loses during the past three decades. Yet, the improvement in efficiency from DES principle may not be remarkable unless the resistance of the rails is important, which occurs at high projectile velocity (velocity skin effect), for long rails or for high resistivity materials. A 12 mm X 12 mm square bore railgun, using a solid metal armature, with several energy feed-in points distributed along the length of the gun was designed to test the DES railgun concept. The gun was powered by pulsed-power supply with a total stored energy of 1 MJ at 10 kV. Simulation model for the system was built up to analyze its performance. With a fixed rail material, simulations were made with different energy level of the pulsed-power supply and different length of the rails. Comparisons between the results of DES configuration and breech-fed ones were made. With a 9.5 m long DES railgun, and the capacitor banks charged to 6 kV, 8 g projectiles could be accelerate to 4391m/s through the simulation, the overall efficiency of the system could be increased from 23.7% to 26.8% in comparison with a breech-fed one. It can be seen from the simulation result that with a certain rail material, the DES configuration would give significant improvement in railgun performance, only when the rails are sufficiently long and the velocity of the projectile is high enough.