Experimental Investigation of Projectile Integrity While Driving Through an Axisymmetric Baffled and Railed Ram Accelerator

Abstract

Investigations of the operational envelope of a baffled and railed axisymmetric ram accelerator occasionally yield anomalous results where large pressure spikes precede a large drop in performance. Using experimentally obtained pressure data in tandem with ANSYS structural analysis modules, Finite Element Analysis (FEA) was per- formed to assess the structural integrity of the ram accelerator projectile. Utilizing pressure fields from experiments, FEA indicated that the polycarbonate sub-caliber projectiles used in these tests experience plastic deformation and compromised struc- tural integrity. Similar analysis was also conducted using a sturdier 6061 aluminum projectile which resulted in no deformation or factors of safety below 1; however, these projectiles are significantly heavier and less scientifically useful. A 2-piece shell projectile made of 7075 aluminum was then designed in order to reduce weight and maintain the increased strength of the aluminum relative to the polycarbonate. The shell style projectile showed minimal internal deformation and no external plastic de- formation when subjected to the same high pressure as the polycarbonate, suggesting this projectile be used in future experiments where high pressures occur.