Study on the effect of lunar rock powder distribution states in a temporary storage cup on micro-quantitative sampling performance

Accurate and repeatable micro-quantitative sampling of lunar rock powder is essential for lunar in situ analysis and in situ resource utilization (ISRU). In the investigated workflow, powder is dumped by a shovel into a temporary storage cup before sampling, and variations in its distribution can cause large fluctuations in sampling mass. Three-dimensional scanning was used to characterize 100 dumping tests, from which five representative heterogeneous distribution states were identified. An additional homogeneous state was obtained through preconditioning, and the six states were quantified using mean stacking height, stacking height standard deviation, and effective powder proportion. Theoretical analysis and discrete element simulations were conducted to investigate the influence of lunar gravity on powder deposition and reconstruct representative distribution states. Ground-based tests showed that most heterogeneous states caused insufficient or unstable sampling, whereas the homogeneous state yielded 105.7 mg with a deviation within ± 10 mg. Under the tested conditions of a 4 g powder input and a 30 N downward load, a stacking height standard deviation below 4.5 mm and an effective powder proportion above 80% were identified as empirical screening criteria for stable sampling. These results provide guidance for regulating powder distribution in lunar micro-quantitative sampling systems.