Multishot performance of an insulator in a laboratory electromagnetic launcher

Insulator materials for electromagnetic launchers have been extensively evaluated for their performance under plasma armature conditions. Melting, erosion and ablation damage of polymers, glass-reinforced polymers and ceramics have necessitated regular replacement to maintain electrical isolation of rail conductors. A glass-fiber-reinforced polymer insulator from the G series was examined for its performance in a multishot electromagnetic launch (EML) environment employing a solid aluminum armature. Bore surveys were conducted between launches to monitor the condition of the insulator surfaces. Techniques to assess degradation by debris deposition, matrix ablation and gross delamination utilized an in situ optical bore scope and an internal bore gage that measured insulator-to-insulator dimensions in the medium caliber square bore. The widely used, glass-reinforced polymer insulator G10 was found to maintain its electrical integrity over multiple launches. The extent of degradation was found to be dependent upon the magnitude of the local energy dissipation and corresponding location within the gun bore. Measures to control damage through materials engineering can be developed from this knowledge base.