Ozaki S, Ishigami G, Otsuki M, Miyamoto H, Wada K, Watanabe Y, Nishino T, Kojima H, Soda K, Nakao Y, Sutoh M, Maeda T, Kobayashi T
Yokohama National University, Yokohama, Japan.
Keio University, Yokohama, Japan.
NPJ Microgravity. 2023 Aug 8;9(1):61. doi: 10.1038/s41526-023-00308-w.
Studying the gravity-dependent characteristics of regolith, fine-grained granular media covering extra-terrestrial bodies is essential for the reliable design and analysis of landers and rovers for space exploration. In this study, we propose an experimental approach to examine a granular flow under stable artificial gravity conditions for a long duration generated by a centrifuge at the International Space Station. We also perform a discrete element simulation of the granular flow in both artificial and natural gravity environments. The simulation results verify that the granular flows in artificial and natural gravity are consistent. Further, regression analysis of the experimental results reveals that the mass flow rate of granular flow quantitatively follows a well-known physics-based law with some deviations under low-gravity conditions, implying that the bulk density of the granular media decreases with gravity. This insight also indicates that the bulk density considered in simulation studies of space probes under low-gravity conditions needs to be tuned for their reliable design and analysis.
研究覆盖外星天体的风化层（细粒颗粒介质）的重力相关特性，对于太空探索着陆器和漫游车的可靠设计与分析至关重要。在本研究中，我们提出一种实验方法，以在国际空间站离心机产生的稳定人工重力条件下长时间检查颗粒流。我们还对人工重力和自然重力环境中的颗粒流进行了离散元模拟。模拟结果证实，人工重力和自然重力下的颗粒流是一致的。此外，对实验结果的回归分析表明，颗粒流的质量流率在低重力条件下定量地遵循一个著名的基于物理的定律，但存在一些偏差，这意味着颗粒介质的堆积密度随重力减小。这一见解还表明，在低重力条件下对太空探测器进行模拟研究时所考虑的堆积密度，需要针对其可靠的设计和分析进行调整。
