A Vertical Ballistics Range with Photon Doppler Velocimeter Instrumentation for Projectile Penetration Testing in Soils

The operation of a vertical-firing ballistic range is described, along with instrumentation to produce high-resolution velocity-time measurements of projectile penetration in sand targets. The range comprises a single-stage gas gun with a 14.45-mm-inner-diameter smooth-bore barrel and a maximum operating pressure of 300 bar. The launch mechanism is a combination of an electropneumatic solenoid valve and a fast-acting shuttle valve. The gun loading curve is determined for projectiles having a mass of approximately 35 g. The launcher efficiency, defined as the ratio of the actual muzzle velocity to the theoretical prediction, assuming the isentropic expansion of the compressed helium gas, is calculated as a function of the reservoir pressure. A conventional photon Doppler velocimeter (PDV) was designed and assembled on the range to directly measure the projectile velocity-time history during flight and penetration into soil targets. Magnetic sensors were used to trigger the data acquisition system. Additional magnetic sensors were assembled to measure the projectile muzzle velocity when steel projectiles were used. Loose- and Densely-packed soil targets were prepared by means of pluviation. Results from shots into loose and dense sand were analyzed, demonstrating the significance of the soil target packing in the penetration resistance of sand.