Penetration of Explosives by Shaped-charge Jets

Shaped-charge penetration of explosives is studied analytically and experimentally. Two models are developed, each applicable to a different regime of jet velocity. The first addresses high-velocity penetration. If a jet is sufficiently fast, its penetration velocity will exceed the explosive's detonation velocity, and the process may achieve a steady state with the crater following the detonation wave. The model predicts that penetration per unit jet length is about 15% less than that predicted by the density law, a reduction similar to that predicted by the compressible theory for inert compressible materials. A second model addresses slower penetrations where the detonation wave precedes the penetration process to consume all the explosive. Later, the explosive product gases may, if confined, reach equilibrium at a high pressure, and penetration may then achieve a steady state. This model, which applies compressible penetration theory to a target of ideal gas, predicts that, at low jet velocities, the initial high pressure of the gas greatly reduces the penetration. Comparison of this model with some experimental results shows excellent agreement provided foreshortening is taken into account.