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UBC Theses and Dissertations

Performance of the UBC two-stage light-gas gun Deforge, David James


The performance of UBC two-stage light-gas gun and the associated diagnostics systems were examined under a variety of shot conditions. In the gas gun, the expansion of gas from burning gun powder propels a piston which, in turn, compresses and accelerates the low molecular weight pump gas. The rising pressure of the pump gas eventually opens a petal valve permitting the pump gas to propel a projectile towards the target. At the front of the projectile is a metal disk - the flyer plate. In a typical experiment, the behaviour of the target material under the high pressure conditions that result from the impact between the flyer plate and the target is examined. In this study, the use of gun powder loads of 46 to 150 g, with helium pump gas, resulted in projectile velocities between 2 and 4 km/s for 5 to 9 g projectiles. The ability to measure the projectile velocity with 0.2% uncertainty was demonstrated. Such resolution is comparable to those obtained with systems used by other researchers. The internal ballistics of the gun were modelled with a 1½ dimension Arbitrary Lagrange Eulerian computer code. The calculations had limited success in obtaining the measured projectile velocity. The calculations were also used to estimate the time difference between the arrival of the piston at a preset location along the pump tube and the arrival of the projectile at a given distance from the muzzle of the launch tube. These calculations showed reasonable agreement with the measured values. Experiments were also performed to examine the orientation and curvature of the flyer plate on impact with target. The size and orientation of the tilt of the flyer plate were relatively reproducible for shots with large copper flyer plates in primarily stress-free sabots. The tilt values with these projectiles were less than 10 mrad. It was also demonstrated that the flyer plate curvature was consistently concave for copper flyer plate projectiles with radii of curvature of approximately 1 m.

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