Hole size from impacts at simulated velocities to 23 km/s

A method is described that allows penetration of thin aluminum plates at velocities up to 23 km/s to be simulated in experiments conducted at actual velocities below 7 km/s. This is accomplished by replacing the impactor and plate materials by an appropriate surrogate material that reproduces, at modest impact velocities, the important physical mechanisms that occur in a higher-velocity aluminum impact. Dimensional analysis is used to identify the similarity conditions that must be satisfied by the surrogate material. Cadmium is shown to be an excellent surrogate of aluminum that provides a velocity magnification factor of 3.1. Measurements of hole size from aluminum impacts at velocities up to 7 km/s are found to agree well with cadmium tests at the corresponding reduced velocities. Cadmium results are used to provide estimates of hole size for aluminum impacts at velocities up to 23 km/s.