Gas permeability of BP-1 lunar regolith simulant at sub-atmospheric pressures

The risks to lunar surface assets from high-velocity regolith ejecta particle streams have significant implications for the sustainable human exploration of the lunar surface. Such regolith can result from lander engine plume-surface interactions. Consequently, the gas permeability of lunar regolith must be understood for precise plume surface interaction ejecta acceleration models. Motivated by these risks, and with the goal of supplying future plume surface interaction models with improved input parameters, the objective of this study is to understand the gas permeability of lunar regolith simulant BP-1 at sub-atmospheric pressures while considering density and moisture content variations. The Regolith Gas Permeability Tester (REGAPT) presented here is a purpose built transparent permeameter that allows the flow of gas to be controlled through the BP-1 once the whole system has reached pressures below 130 Pa. Results from REGAPT demonstrate a range in BP-1 gas permeability from 0 . 4 × 1 0 − 13 m 2 to 1 . 9 × 1 0 − 13 m 2 . Higher densities and lower porosities reduce permeability as expected. Outgassing from residual moisture in BP-1 is found to bias gas permeability measurements. It is therefore important to carefully control the moisture content of lunar regolith simulants in experimental studies that involve gas flow, such as those investigating the effects of plume surface interactions. • The permeability of lunar regolith influences gas flow during descent engine plume surface interactions. • A custom permeameter is used to determine the low pressure permeability of lunar regolith simulant BP-1 including contributions from viscous and non-viscous flows. • Density and moisture content are varied in the tested BP-1 samples. • For three different sample densities and three different moisture content levels, the permeability of BP-1 is found to range from 0 . 4 × 1 0 − 13 m 2 to 1 . 9 × 1 0 − 13 m 2 . • Moisture content outgassing is seen to bias permeability results and greatly complicates pump down.