An efficient impact sampling strategy for small-body regolith: Dependence of collected mass on projectile ejection

Abstract

Impact sampling on small bodies has been proven feasible. However, particle flow laws during regolith sampling are unclear, and existing sampling mechanisms have significant potential for improvement. In this study, the discrete element method and multi-body dynamics (DEM-MBD) coupling model is used to explore the particle flow laws, and an efficient impact sampling strategy is developed which can significantly improve the collected particle mass. Two projectiles are placed symmetrically around the end of the sampler and fired simultaneously. In the event that only one projectile is successfully fired, the collected mass is still 7.9 times higher than that of existing sampling method. As particles accumulate near the transporting pipe, a clogging state occurs and obstructs the particle flow, causing the mass flow rate to drop rapidly. Particle clogging can be effectively reduced using a sampling strategy in which the probe reaches the target position and then fires the projectiles. We show that the particle-probe interaction can interfere with position and attitude of the probe and eventually reduce the collected mass of particles. To solve this problem, a proportional derivative (PD) controller is designed to stabilize the attitude and position of the probe. An ejection angle of 54° can significantly improve the sampling efficiency by balancing the number of driven particles and vertical velocity, and the particle mass obtained is 31 times higher than that of the existing method.