Regolith Cohesion Measurement via Induced Electrostatic Lofting

Abstract

Electrostatic dust lofting has been hypothesized to occur on airless bodies such as the Moon and asteroids, but in-situ evidence of this phenomenon has yet to be observed. Nonetheless, experiments and numerical models have provided insight into the fundamental physics of electrostatic dust mobilization. Prior to lofting, grains are bound tightly to the surface by cohesion, the dominant force for sub-mm particles. However, the magnitude of cohesion in regolith remains poorly constrained. We introduce the design of the Electrostatic Sample Collection and Cohesion Quantification (E-SACCQ) system, a technology that induces electrostatic dust lofting to measure regolith cohesion. E-SACCQ induces electrostatic lofting of charged regolith grains via a biased attractor plate and simultaneously images their size and trajectory. Since the local gravity is known and the electrostatic force on the regolith grains is controlled by the attractor plate potential, it is possible to solve for the cohesive force on the grains. Furthermore, the ability to induce electrostatic lofting may also provide a new method of dust removal from spacecraft surfaces and for sample collection on rubble pile asteroids, which may not have suitable, powdery surfaces for conventional scoop style collection methods. In this work, we discuss the preliminary design of the instrument. The feedback between the E-SACCQ electrode and the near-surface plasma environment is numerically modeled. Our models predict that solar wind bombardment will be a significant perturbation to the electric field between the surface and the electrode. The system's sensitivity to key design parameters such as attractor plate potential, size, and operating distance above the surface are also assessed. With respect to grain characterization and position tracking, stereo vision is selected as the preferred solution. Additional plasma simulation modeling and experimental demonstration is required to mature this technology.