An Investigation of the Protection Afforded a Spacecraft by a Thin Shield

Results are presented from a theoretical and experimental program to investigate the damage that would be inflicted upon a missile, satellite, or space vehicle by a hypervelocity particle. Most of the work has been directed toward thin shield impacts. The problem is treated theoretically by examining the wave motion in an impacting projectile and shield, and consideration is given to heating effects. Theoretical considerations and experimental results lead to the following conclusions: 1) A thin shield is effective because it fragments and spreads the projectile and shield debris and, at high velocities, may melt or vaporize the fragments. 2) The optimum shield to minimize penetration is the one that melts or vaporizes the majority of debris coming through the shield. The shield thickness required to do this is found to decrease with increasing impact velocity. Total damage is not denned on this basis only, and failure may occur through momentum loading of the shielded structure. 3) Shield parameters such as strength and density, on an equiweight basis, are not important. 4) Hole diameter in a shield is proportional to impact velocity and to shield thickness to the twothirds power.