Design and Test on Pyroshock-reduced Separation Device

摘要

Various types of pyrotechnic separation device have been developed for military and aerospace applications. Due to high reliability and simple design scheme, explosive bolt with built-in high explosives has been generally employed to break the bolt for separation and developed to reduce debris or fragmentation with improved computational analysis methodology. Fracturing hard steel, however, results in high pyroshock more than 10,000 g, which limits its location and application away from shock-sensitive devices such as electronics. In order to get rid of pyroshock contribution coming from material fracture, we studied ball-release mechanism, which is also generally adopted for pyrotechnic separation device. Compared to explosive bolt, this pyroshock-reduced separation device (PSD) using ball-release mechanism needs high pressure generated from combustion of explosives rather than Shockwave from detonator. We notice the ball engagement is critical in the reliable separation and develop new design. Before firing, almost half volume of ball is locked inside the housing and rest volume is in the bolt. Therefore our separable rod or bolt is positioned between the housing and piston by means of balls, which allows stable ball positioning and also the cross-section of piston to be small enough to contain balls for smaller initial free volume. After firing, balls would drop inside the piston. We perform static separation tests using hydraulic tester for the actuation instead of pressure cartridge. By measuring the dependence of separation load on the ball position, we can figure out the optimum distance between the housing surface and the center of the ball. We also perform dynamic separation tests using pressure cartridge. By measuring the dynamical pressure inside the device and load applied to bolt we could estimate the margin of dynamic separation safety.