A diagnostic technique for understanding startup of metal armatures

Metal armature performance throughout a launch is affected by the initial loading conditions. An improper fit at startup reduces the desired contact loads and leads to increased power dissipation at the armature-rail interface which affects both armature performance (at startup and throughout the launch) and the rail life. Ensuring proper fit and understanding the initial contact loading condition is hard to do in high performance railguns because they are built without any room for instrumentation. In a recent program, we designed and built a specialty railgun with one side made of clear material to allow for visual examination and used high speed photography (25,000 frames per second) with an instrumented rail and armature to understand the effects of initial contact loading on the armature performance. In this paper, we describe the technique used, present typical test data, and summarize the findings