Vacuum experiment recreates spacecraft landing hazard

Successfully landing a spacecraft on another celestial body may seem like the victorious climax of a mission that was likely years in the making. But the touchdown moment itself can present its own challenges due to the interaction of the thruster plume and the dusty surface. Exhaust from the thrusters kicks up regolith and rocks that can impede vision and damage sensitive components. Understanding this effect is crucial for space mission planning.

Subramanian et al. employed a large-volume plume-regolith facility to study the effects of ejected regolith in near-vacuum conditions. Using particle image velocimetry (PIV), they tracked particles produced by a simulated engine nozzle and determined their velocity and ejection angle. The authors hope their experimental data will supplement existing theoretical models.

“Numerous numerical investigations have been conducted in an effort to understand the dynamics of ejecta in the lunar environment,” said author Senthilkumar Subramanian. “However, the interaction between plumes and regolith remains largely unknown as a result of insufficient experimental data.”

The researchers created their simulated regolith using glass microspheres of varying densities to simulate the surfaces of both large bodies like the Moon and smaller objects like asteroids. In both cases, the plume created a triangular-shaped sheet of particles with maximum velocities of up to 100 m/s. The low-density particles reached faster velocities, higher elevations, and covered a larger spatial area.

Ultimately, this experimental data will lead to better predictive models and more successful landings for the next generation of space missions.

“Research in this plume regolith interaction can help develop strategies to mitigate dust production during landing and its impact on lander instruments,” said Subramanian.

Source: “Tracking plume-regolith interactions in near-vacuum conditions,” by S. Subramanian, A. Wilson, C. White, K. Kontis, D. Evans, and J. Van den Eynde, Physics of Fluids (2023). The article can be accessed at https://doi.org/10.1063/5.0180669 .