Experiments to measure melt-wave erosion in railgun armatures

This paper describes experiments to measure melt-wave erosion (MWE) damage in railgun armatures. C-armatures were launched on the Medium Caliber Launcher at the Institute for Advanced Technology (IAT), Leander, TX, and recovered by "soft catching" in a tube filled with cotton rags. Recovered armatures were mechanically profiled to measure erosion depth as a function of position on the contacting surfaces. Although recovered armatures provide only a final snapshot of the erosion process, one can show how erosion proceeds by recovering armatures at different stages of the launch. This type of study requires the use of a crowbar switch at the breech of the railgun to rapidly shunt current out of the armature, thereby interrupting the erosion process at the desired point in the launch. We describe the experimental setup and summarize the results of 11 experiments. The experiments investigated the effect of linear current density (ranging from 35 to 45 kA/mm) and rail material (copper and aluminum) on MWE damage. Lastly, we present some thoughts on contact transition mechanisms that, in some cases, prevented the collection of MWE data.