Impact of Corroded Copper Rails on the Performance of a Miniature Electromagnetic Launcher

The U.S. Navy is getting much closer to fielding shipboard railguns. As they get closer, there is increasing concern with how corrosion of the rail surface will affect launcher performance and lifetime, with it intuitively hypothesized that corrosion will negatively affect both. It is anticipated that significant surface-oxide formation on the rail surface will increase the rail/armature contact resistance, and surface pitting/deposition will further affect the rail/armature contact area. There are several negative effects that could arise from surface corrosion on the rails. One includes an increased probability of armature transition occurring that can significantly decrease launcher efficiency and muzzle velocity, and enhance the rate of rail erosion. In the experiments discussed here, the University of Texas at Arlington has performed two sets of experiments aimed at better understanding how corrosion impacts the performance of a 1-m long railgun with muzzle energies of roughly 1.8 kJ (14 g to roughly 450 m/s). In the first experiment, virgin C11000 rails were shot on five times, and after the shots, the rails were segmented and characterized using an optical microscope and X-Ray diffraction. In the second set of experiments, bare C11000 rails were corroded, using a custom salt fog chamber for 96 h, before being shot on five times and then surface characterized in the same manner. The launcher has a peak current of roughly 100 kA, and launch packages fabricated from 6061-T6 aluminum are used. The rail claddings studied have dimensions of 1 in $\times 39.4$ in $\times 1$ /8 in. The railgun performance was evaluated using the standard measurements of armature current and muzzle voltage. The results of both experimental test series will be presented here.