Analysis of HEMCL Railgun Insulator Damage

Abstract : Severe insulator damage is regularly observed near the one meter location and beyond in recent high energy, high current tests in a 4 meter railgun. Analyses of the damaged insulator surfaces were conducted to determine the source of this damage. Laser pulse heating tests were performed to simulate effects observed on the insulators. The analyses show that the primary damage to the insulators is in the form of epoxy pyrolysis, and glass fiber softening and liquification. It is concluded that the damage source is plasma heating. Plasmas are expected in these systems because of the presence of high rail-to-rail voltages behind the armature; the magnitude of these voltages reaches peak values near the one meter location where the damage is most severe. In an earlier study, severe thermal damage was found on the steel rail surfaces adjacent to the damaged insulators; this damage was also attributed to plasma heating.