Experimental Method for Measuring Cohesion of Regolith via Electrostatic Lofting
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The hypothesized electrostatic lofting of individual regolith grains on the Moon and asteroids has been investigated extensively in laboratory studies. Cohesion may dominate how regolith behaves on these small, airless bodies, yet the magnitude of this force remains uncertain. We induce the electrostatic detachment of dust as a mechanism to break cohesive bonds between individual zirconia-silica microspheres in order to measure the interparticle cohesive force between them. A high-speed camera imaged centroid positions of the lofted microspheres over time. Using the centroids from the initial detachment, we numerically calculated initial accelerations to solve for the cohesion that had been restraining the microspheres. Unexpectedly, the electrostatic lofting of clumps of particles was observed and experimental results showed that clumps were a non-negligible portion of the lofted object population.
A PCO Dimax CS3 was used to take high-speed images at 945 frames per second of electrostatically lofted clumps of zirconia-silica microspheres. The images were processed and analyzed in Matlab using Matlab built-in functions. The two-dimensional centroid positions of lofted objects of interest were identified and their trajectories were tracked. The velocity and accelerations of tracked objects were then numerically calculated in order to solve for the cohesion, and compared to other independent methods.