Early-stage ejecta velocity distribution for vertical hypervelocity impacts into sand

The ejects dynamics during main-stage excavation flow in a cratering event have previously been well characterized, particularly for vertical impacts. In this experimental study, we present new results addressing the early-time, low-angle, high-speed component of the ejecta velocity distribution as a function of time for hypervelocity vertical impacts into sand. Although this regime represents a very small portion of total ejected mass in laboratory experiments, it comprises a greater percentage of growth for larger craters. (C) 2010 Elsevier Inc. All rights reserved.