An experimental investigation of plasma armature railgun performance in the 3.2 to 4.2 km/s regime

The authors describe a set of experiments in which velocities up to 4.2 km/s were achieved in a midsize gun (51 mm) without discrete secondary arc formation. A figure of merit is described which relates the muzzle velocity to the electrical action applied to the barrel during acceleration. This figure of merit declines from the lower to the higher velocity firings. An efficiency roll-off in a mid-sized railgun as the launch velocity increased from 3 to 4.2 km/s was observed. The momentum efficiency in the velocity regime was measured at approximately 75%. Armature behavior was monitored closely in each shot of the eight shot high velocity test series. No armature bifurcation was observed but data from the induction probes strongly suggest that the armature current distributed included a long tail that increased in length throughout the launch time. Finally, it is noted that the changes made to the bore configuration to perform the high velocity test series also appear to have had a beneficial effect on bore lifetime