Gas transport modeling and disturbance-suppression strategy during vacuum depressurization of lunar regolith simulant

Abstract

Ground-based vacuum tests of lunar-regolith-related systems require granular simulant beds to be depressurized without disturbing the sample or contaminating the vacuum chamber. Delayed pore-gas release may generate transient internal–external pressure differences and induce particle ejection. This study proposes a disturbance-suppression strategy combining multi-channel outgassing with stepwise pressure reduction and develops a reduced-order model based on fractal porous-media and gas transport theories to predict the pressure-reduction time required for pressure equilibration. Four vacuum tests were conducted using HIT-LRS-H lunar regolith simulant. Pronounced disturbance occurred in Test 1 under insufficient outgassing paths and pressure-reduction time, whereas no pronounced visible disturbance was observed in Tests 2–4. For Tests 2–4, the predicted pressure-reduction times agreed with the experimental results within ± 10 % . Parametric analysis showed that the pressure-reduction coefficient and outgassing-path geometry dominated the equilibration behavior, whereas relative density had a secondary effect over the investigated range of 50%–92%. Under the present test configuration and operating conditions, k p ≥ 0.7 was preferred within the investigated range, and the required pressure-reduction time reached a local maximum near 1000 Pa. The proposed framework provides a quantitative reference for designing outgassing structures and stepwise depressurization schedules in ground-based vacuum tests under comparable material and operating conditions, while further validation is required before extrapolation to other simulants or in-situ lunar conditions.