Effect of railgun electrodynamics on projectile launch dynamics

A series of experiments were conducted for examining the disturbances acting upon a subprojectile during electromagnetic launch. This investigation uses a number of performance indicators, including target impact dispersion, to quantify the causes. The effects of armature contact configuration and in-bore acceleration profile on the launch process were considered. The test program consisted of two armature contact configurations and two in-bore accelerations. Twenty-eight shots were fired, of which 15 were slugs. For the test matrix, the nominal exit velocity was 1100 m/s. The in-bore acceleration profile was varied by diverting the armature current with a time delayed closing switch, located at the muzzle of the railgun. Effects from the launch disturbances were quantified by use of flash X-rays, smear camera photography, and yaw card and target impacts. The time-rate-of-change of launcher and switch currents and launcher voltages were measured. Results indicate significant differences in ballistic performance for the two front contact configurations. Also to a lesser extent, differences were observed for the two in-bore acceleration profiles. In-bore dynamics initiated from the deviation from the bore centerline are believed to cause these differences.