Crater formation and particle ejection induced by supersonic jet impingement in near-vacuum

This study investigates the formation and evolution of craters under near-vacuum conditions due to supersonic jet impingement, with a focus on regolith particle ejection dynamics. Experiments were conducted at the Plume-Regolith Facility of the University of Glasgow, where controlled jet pulses (0.1, 0.5 and 1.0 s) were directed to high- and low-density regolith simulants. Using Particle Image Velocimetry (PIV) and infrared imaging, the crater morphology and ejecta distribution were analysed over multiple sequential jet pulses. The results indicate that the high-density regolith forms compact, steep-walled U-shaped craters, while the low-density regolith produces larger, sloped V-shaped craters. Longer pulse durations result in increased crater expansion and higher ejection angles. In particular, steep-walled craters promote high-angle ejection near the nozzle axis, posing potential risks to spacecraft landers. Regardless of regolith density, expelled particles exhibit ejection angles between 40°and 50°, suggesting long-distance travel in low-gravity environments. These findings improve our understanding of plume-regolith interactions and contribute to safer planetary landing strategies by informing numerical models and spacecraft design considerations.