Lunar dust removal and material degradation from liquid nitrogen sprays

Abstract

Lunar regolith degrades human health and equipment making mitigation paramount for lunar missions. Cryogenic liquid sprays are a recently developed, simple, and convenient concept for dust mitigation in a lunar environment. However, removal efficacy and material degradation under the extreme cryogenic vacuum environment are unknown. Traditional space suit dust mitigation technologies used on the Apollo missions, such as brushing and vacuuming, introduced suit fabric abrasion which must be addressed for all dust mitigation methods considered for lunar implementation. This publication reports the efficacy of dust removal in a simulated airlock vacuum environment and the associated impact of repeated dusting-washing cycles on spacesuit materials. Specimens were impinged with measured liquid nitrogen sprays at different spray angles within a vacuum chamber. Mean mass removal of 98.4% was achieved in a vacuum environment at optimal conditions, correlating to 95.9% removal of particles below 10 μm. To investigate material degradation, a total of 26 samples were cycled a cumulative 233 times through cryogen spray washings under ambient conditions. A degradation scale was created to classify optical microscopy observations. Degradation results indicate minimal spacesuit material abrasion from liquid nitrogen removal. Results additionally show an average of 2.66% increased removal with each subsequent washing cycle for fabric washed twice, possibly due to clogging and occupancy of specific sites. The conclusion is that liquid nitrogen sprays cause relatively less damage than conventional dust mitigation techniques, even under the extremes of cryogenic temperatures and vacuum.