Title: Compaction of Lunar Regolith for Dust Mitigation

Fine dust knocked off the lunar surface during manned and unmanned exploration activities poses a range of hazards to equipment and astronauts. This experimental program will study the effects of compaction of the lunar regolith on the amount of fine particles that are knocked off the surface, and at what speeds. Previous microgravity experiments with JSC-1 lunar regolith simulant showed, serendipitously, that at a relative density of 0.5 or higher the amount of dust knocked off the surface is small. This project will involve samples of lunar regolith simulant in sealed evacuated containers at predetermined relative densities. (Relative densities are a measure of the compaction of a granular material.) The samples will be maintained at the desired relative densities through spring-loaded tops to the sample containers. During lunar-g parabolas, a sample will be exposed and subjected to a series of impacts at increasing energies. High-speed video will capture the amount of dust ejecta produced and enable post-flight measurements of the velocity distribution. The samples will be large enough so that boundary effects of the container do not affect the response of the sample to the impacts (~10 times larger than the impactor). A typical sample container might be a cylindrical box ~20 cm in diameter and 10-20 cm in depth. The samples need to be evacuated because air has a strong lubricating effect on the motion of granular media. Impacts on the surface can be accomplished with a piston mechanism driven by a solenoid, or spring-launched projectiles. Results will be a measure of dust ejecta mass and velocities as a function of impactor energy and regolith relative density.

Robert Mueller

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