Vertical Projectile Launcher for Study of Rapid Penetration into Soil Targets

Abstract

The majority of ballistic experiments in granular media in the literature involve horizontally launching projectiles. Notwithstanding the significant scientific findings resulting from these studies, the depth-dependence of geostatic stresses is not captured in a horizontal configuration. The design and performance of a vertical ballistic range is described herein. The range is capable of launching projectiles at impact speeds of up to 900 m/s into soil targets. A pluviator is employed to prepare sand targets with precise and highly repeatable bulk densities. Use of a photon Doppler velocimeter (PDV) and other instrumentation to track projectile velocity both in-flight and during penetration into the soil target are elucidated. A relationship is found between the muzzle velocity and chamber pressure. Launcher performance is quantified by comparing measured muzzle velocities with theoretical velocities calculated from isentropic expansion of gas behind the projectile in the launcher barrel. It is found that the launcher efficiency is in the range of 70 to 90%, with efficiency increasing for heavier projectiles. The PDV instrumentation developed for the range successfully resolves projectile velocities in flight and during penetration into the soil target.