Minimizing non-arcing contact material deposition on rails

Material deposition on the rail in railguns from sliding armatures during nonarcing contact phase must be minimized to meet the Electromagnetic Armament System Focused Technology Program (EMAS FTP) program requirement for rail variation over the life of the barrel. The authors conducted a preliminary investigation of material deposition in Phase 1 of EMAS and found material combinations which have the potential of minimizing material deposition. They postulated that deposition can be minimized (or eliminated) if the material combination has "poor wetting" capability. They identified candidate material combinations and experimentally measured their wetting capability, For copper contacts, chromium and tantalum were the best rail material candidates. In this paper, the authors describe the physics of "wetting", describe the experiment used to measure the wetting capability of various armature and rail material candidates and present the results of the wetting experiment.<>