Deceleration of projectiles in sand

Abstract

This study investigates the deceleration dynamics of projectiles during vertical penetration into silica sand targets up till the final depth of burial (DoB). Experiments were conducted with cone cylinder rods launched vertically into sand targets using a compressed air gun. Velocity–time records were obtained using a multichannel homodyne photon Doppler velocimeter (PDV) which tracked the back face of the penetrator as it decelerated, supplemented by high-speed video cameras from two views. A Poncelet framework was employed to describe the velocity–penetration relationship and drag and resistance coefficients were extracted by fitting the experimental measurements. Experiments were performed in dense and loose sand at a nominal impact velocity of 200 m/s, and experimental excursions were conducted with modified launch parameters. Mean drag and bearing resistance coefficients were found for sands under dry and wet pore saturation, as well as loose and dense packing. The work contributes essential insights for predicting the DoB of projectiles, particularly relevant for environmental remediation efforts in formerly used military sites.