Crater damage to a thick plate via hypervelocity impact can be predicted from the tensile strength established by standard metallurgical techniques. Some of the results indicate that the frequently quoted empirical rule that the thickness of a plate that will just prevent penetration by a high-velocity particle is approximately 1.5 times the depth of the crater that it would make in a very thick plate is rather questionable; factors from 1.4 to more than 2 have been observed. In order to acquire reliable data relevant to the impact behavior of bumpered structures, impact spray cones of fragmented particles were studied. Low-density material placed in the bumpered structure significantly alters the impact spray cone; the data suggest that such hull systems might be either 15% lighter or as much as 75% thinner (due to reduced spacing between the skins) for given protection.