Flowability of lunar regolith simulants under reduced gravity and vacuum in hopper-based conveying devices

This paper reports on a series of experiments that were conducted on a partial-g parabolic flight campaign to determine key parameters of hoppers, designed for regolith sampling, science experiments, or in situ resource utilization (ISRU) processes on Moon or Mars. A major problem related to these applications is the clogging of feeding and conveying devices due to the physical properties of the regolith. In the experiments the flow rate of two representative lunar regolith simulants (JSC-1A and NU-LHT-2M) through hoppers was investigated under low vacuum conditions and reduced gravity. The effect of gravity, hopper outlet width, and hopper inclination angle on the sample flow was determined. It was found that both gravity and outlet width influence the flow rate of the investigated regolith simulants linearly. The effect of the inclination angle was visible, but no general relation to the flow rate could be determined. No specific difference in flow rate was observed between the two investigated sample types. Furthermore we observed lower sample compaction under reduced gravity, occurrence of abrupt dust release during sample flow under higher ambient pressures, and random arching and related flow rate restrictions.