Muzzle-fed railgun experiments with 3-D electromagnetic simulations

The UTSI 2.4 m transaugmented railgun was reconfigured so that current was fed from the breech to the muzzle along the outer rails and then returned to the armature along the inner rails. Experiments were performed using plasma armatures at peak currents of 70 and 100 kA. At a peak current of 100 kA the measured increase in projectile velocity was approximately 500 m/s; less than half of that obtained from a conventional configuration in the same railgun, and considerably less than predicted for the muzzle-fed configuration. B-dot probes showed that the armature was very compact, but separated from the projectile soon after fusing. Three-dimensional (3-D) finite element electromagnetic simulations on the UTSI railgun structure showed that the electromagnetic force on the armature was much less than predicted by the simple force model. The reduction in force was due primarily to axial forces exerted in the rails.>