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The sliding electrical contact (SEC) between rails and armature is a focus in electromagnetic rail launchers. The extreme conditions, such as high current density, high temperature, and high contact pressure, influence SEC performance. In this article, the segmented rails were used to study the effects of launch mass on SEC. Two groups of experiments, armatures with and without launch mass, were carried out. The mass difference of rail parts was measured, the macro- and micromorphology of rails surface were observed, and the driving current and muzzle voltage were obtained. Three conclusions are obtained: 1) the mass difference of rail parts in shooting with launch mass is greater than that without launch mass, due to the high temperature of armature contact surfaces; 2) because of the electron migration, the mass difference of the cathode rail is larger than the anode rail; and 3) the contact resistance between rails and armature without launch mass is lower than that with launch mass, result from the large contact area. Moreover, the current density and the temperature of the armature and rails were calculated. Results show that the temperature of surface of armature with launch mass is higher than that without launch mass. In a word, based on the results from experiments and simulations, the launch mass improves the sliding electric contact performance. [ABSTRACT FROM AUTHOR]

Armature ejecta, which erodes the insulator and reduces surface dielectric strength, has been considered as a threat to solid-armature launchers. Two series of experiments were carried out in a small caliber launcher (SCL) to investigate the sources of armature ejecta and degradation mechanisms of the insulator. In first series of experiment, the ejection of armature was imaged by a high-speed camera. The influence of linear current density on ejection was studied in second series of experiment. Mass difference of insulator samples was used to evaluate the output of armature ejecta. Insulation performance was judged from the surface flashover voltage. And the degradation mechanism resulted from armature ejecta was analyzed based on the process of surface flashover. Results show that the local breakdown at armature–rail interfaces is one of the sources of armature ejecta. The amount of ejecta on samples increased with linear current density. Average flashover voltages decreased when ejecta increased in Zone A (0–200 mm) and Zone B (200–600 mm). And there was little difference of average flashover voltages in Zone C (600–900 mm). The discharge channel of the post-shot sample was composed of arcs and ejecta. The distortion of the surface electric field and the shorten of creepage distance are degradation mechanisms of bore insulators in solid-armature launchers. [ABSTRACT FROM AUTHOR]