Returning to the moon safely - cratering and ejecta dynamics during plume-surface interactions

Plume surface interactions (PSI) encompass the process wherein a compressible jet (rocket plume) and a planetary granular surface interacts, forming a crater and dust clouds around landing sites. With NASA’s renewed interest in returning humans to the Moon through the Artemis program, a fundamental understanding of the PSI process will be vital for ensuring the safety of future missions. As such, the primary objective of this work is to study the crater formation process and ejecta dynamics due to PSI by employing non-intrusive optical diagnostic techniques. The experiments are carried out in an atmospheric, bench-scale facility that accommodated a nozzle operating at sonic exit conditions and a sand simulant bed. Stereo photogrammetry is used for quantitative 3D reconstruction of the crater, and planar particle tracking velocimetry is employed to study the ejecta dynamics. Temporal evolution of the crater geometric properties is extracted from the crater reconstruction and compared between different nozzle heights. The ejecta dynamics is also characterized by studying its trajectory angle and velocities. Further analysis of the evolution of these properties at different nozzle heights and the mechanisms contributing to the crater formation process will be presented.