Lunar regolith simulant milling under lunar gravity conditions

There is a significant gap in lunar planetary research regarding the beneficiation of lunar regolith under representative conditions. Decreasing regolith particle size can have advantageous effects for metal extraction, oxygen extraction, manufacturing, and energy harvesting. However, particle size reduction methods have not yet been studied in reduced gravity conditions. In this work, we present a novel experiment consisting of three milling methods built to decrease regolith simulant particle size in lunar gravity conditions using a parabolic flight platform. Physical properties such as the particle size and morphology of lunar regolith simulant are evaluated before and after milling to quantify the ability for each milling device to reduce the size of lunar regolith simulant. The samples milled under lunar gravity conditions are quantified against control samples milled on Earth for the same duration to evaluate the effects of gravity on the milling processes. First order rate equations are fit to the particle size reduction, and non-dimensional analyses demonstrates the key controlling parameters of the particle sizes reduction rates and limits include the device geometry, applied stress, gravity magnitude, and cohesion between particles. The results of this study will be used to inform the design of future lunar regolith beneficiation technologies.