Design and experimental study of a tethered self-excavating drilling and coring scheme for lunar deep mining

The development and utilization of lunar mineral resources is an important way to solve the earth’s energy crisis. Drilling and coring, an effective method for lunar section sample collection, is a key prerequisite for accurately identifying the characteristics of lunar resource endowments. Restricted by the extreme lunar environment, energy power constraints, and complex lunar subsurface profiles, current lunar drilling remains hampered by the core bottleneck of insufficient drilling depth. To address the challenge of deep lunar sample collection under low-power conditions, the team proposed a rope-tethered self-excavating drilling coring scheme. A rope-tethered self-excavating drilling coring robot was used to conduct 5-meter-deep drilling and coring tests in lunar regolith simulant. This study revealed the evolution laws governing coring and cuttings transport during the self-excavating drilling coring process in lunar regolith simulant, verifying the feasibility of the drilling scheme. In view of the harsh working conditions of the lunar base, the drilling load evolution law of different bit configurations is proved, and the suitable coring bit configuration and drilling procedure parameters were optimized. The test results demonstrate that: ① During the self-excavating drilling coring process in lunar regolith simulant, the drill pipe achieves efficient cuttings evacuation, with the rotational torque constrained within 4 N·m, thereby enabling reliable acquisition of soil core samples; Borehole inspection results verify that the boreholes formed by this drilling scheme possess smooth walls and excellent stability. ② In boulder and protruding rock drilling scenarios, the PDC bit outperforms the diamond bit in comprehensive drilling performance: it features significantly lower drilling force and load, a notably higher drilling rate, and a substantial increase in rotational speed can remarkably mitigate the drilling load. ③ For lunar soil simulant, an increase in rotational speed can effectively reduce the drilling load, while the coring rate exhibits a trend of first decreasing and then increasing with increasing rotational speed. Under the condition of a constant feed rate-to-rotational speed ratio, both the penetration rate and rotational speed are positively correlated with significant increases in drilling force/load and the coring rate. This implies that a balance between the coring rate and drilling force/load must be considered when selecting drilling parameters. This study can provide a reference for the future unmanned deep drilling exploration of the moon in China.