Science Seminars

Ejecta Evolution and Dynamics from Hypervelocity Impacts

Speaker: Brendan Hermalyn
Date: Thursday, Mar 01, 2012
Time: 4:00 PM to 5:00 PM
Location: LSTB-299, Auditorium

Seminar Abstract:

The ejection of mass during an impact event is a shock-driven process that shapes the distribution of materials on planetary surfaces. Ejection velocities dictate the ballistic emplacement and appearance of ejecta patterns, and are particularly important for interpretation of impact mission data. This talk presents results from new temporally-resolved studies of the early- to main-stage ejecta velocity distribution from hypervelocity impact experiments (up to 5km/s) performed at the NASA Ames Vertical Gun Range into porous particulate targets. The ejecta distribution was examined by using a non-invasive high-speed imaging technique to measure ejecta velocity as a function of both time and launch position. This technique allows measurement of ejecta an order of magnitude faster (and earlier) than captured in previous studies, and reveals early-time, high-speed deviations that reflect the initial conditions and material flow-field inside the transient crater. These results are applicable to interpretations of LCROSS mission data, which used an empty rocket booster as a kinetic impactor to excavate material from permanent shadow on the moon.