Railgun armature arcing voltage drop

Controlling the transition of metal armatures to hybrid armatures is essential for the design of reliable transitioning armatures and launch packages. The basic physics of transition must be understood to control transition. Railgun tests are inadequate to understand the basic phenomena of transition. They have many uncontrolled parameters. Bench-type experiments where all operating parameters can be controlled are needed to understand basic transition phenomena. We designed a pin-on-disk experiment and measured the contact voltage drop across arcing contacts. The tests were conducted with current densities similar to railgun current densities. We also varied the arc gap and velocity. We found that arcing contact voltage for an aluminum contactor on a copper disk is about 40 V and concluded that when the muzzle voltage in a railgun test with a metal armature is greater than 40 V, one side of the metal armature must have transitioned to a hybrid. In this paper, we describe the experiment, the measurement technique, and present the results of the experiment.<>