Soft acceleration of a metal plate by a rail gun plasma

The following situation is considered: A dense plasma armature which has been accelerated to a high velocity in a rail gun is allowed to impact a stationary metal plate. At impact, a shock wave is transmitted into the plate and a shock wave is reflected back into the plasma. For very high plasma velocities, the subsequent behavior depends primarily on the plasma density profile just prior to impact. The appropriate partial differential equations are analyzed in plane geometry and the conditions required to prevent spallation of the plate are determined. These results are compared with the "plasma only" armature plasma profiles predicted by Sloan, and it is shown that the conditions for not spalling the metal are well satisfied. The typical rail gun makes use of a low mass plasma armature to continuously accelerate a more massive solid projectile down the length of the rails. It has been suggested that substantially higher velocities and energies may be achievable with a "plasma only" rail gun-which has no solid projectile, but which has an armature mass comparable to the mass of a solid projectile. Subsequent to the acceleration, the momentum of this high velocity plasma must be transferred to a solid projectile. One way to do this is to simply allow the plasma to collide with the projectile. For this to be of interest, the projectile should not shatter and the energy transfer should be reasonably efficient. The purpose of the paper is to analyze an idealized model of such a collision.