Detailed Characterization of Hypervelocity Firings in a Long 120-MM Gun

The applicability of lumped-parameter interior ballistic models to very high velocity guns is limited by the use of a superimposed pressure gradient to approximate the relationship between the space mean, breech, and projectile base pressures. Even modern two-phase flow interior ballistic models, specifically formulated to address the hydrodynamics of the problem, are largely untested in such regimes. Serious attempts to develop high-velocity solid propellant guns, however, require an accurate modeling capability for concept screening and charge optimization. Firings were conducted in a long 120-mm gun (Ballistic Tube) at a propellant charge to projectile mass (C/M) ratio of about 3 to provide muzzle velocities in the 2 - 2.5 km/s range. The tube was instrumented with pressure gages at 14 locations to determine the experimental pressure-displacement profile. Results were compared to predictions of a classical lumped-parameter code, a state-of-the-art two-phase flow model, and a lumped-parameter code with a recently developed pressure gradient.