Soil flowing characteristics during flexible tube coring for lunar exploration: Modeling and verification

Obtaining planetary soil samples and returning them to the Earth is the most effective solution to detect the distribution and reserves of planetary resources. In order to maintain the stratification and a high coring ratio of soil samples during the sampling process, China National Space Administration adopted a flexible tube coring (FTC) method for the upcoming Chang'e-6 mission. In this paper, the lunar regolith FTC characteristics, coupled with its spiral debris discharge were modeled. Orthogonal experiments were carried out with different drilling parameters using the prepared high-density lunar regolith simulant. The results show that the coring height and coring ratio are greatly determined by the penetration per revolution (PPR) index. The lunar regolith simulant's coring ratio was as high as 90% when the PPR was optimized. The physical and mechanical parameters of artificial lunar regolith were characterized with respect to the PPR index as well as the dynamic flowing of the internal core, with a resulting accurately tuned coring ratio prediction model. Furthermore, the drilling load analysis can be applied to the optimization of drilling parameters employed by Chang'e-6 when collecting lunar regolith.