Influence of lunar regolith compressibility on sampling performance of thick wall spiral drills

Robotic drilling for the Chinese Chang’E 5 lunar sample-return mission

“…Our previous work demonstrated that the dynamic pressure generated by the drill bit during the rotational cutting process is essential for pushing samples into a hollow drill tool (Pang et al, 2023). This pressure is highly influenced by the geometrical parameters of the drill tool and the drilling parameters such as the ROP and rotational speed.…”

“…In the early-stage design and tests of the robotic drill, a peculiar phenomenon was detected. Even though the drilling process was well controlled to avoid choking or jamming, and the cutting conveyance was smooth, the samples could not enter the core pipe, resulting in no sample being collected (Pang et al, 2023). As a robotic drill has a similar strategy, the sampling result of the Soviet Union’s Luna 24 drill also showed that the top 0.6 m was empty, meaning no sample entered the core pipe when the penetration started (Bogard and Hirsch 1978).…”

“…Previous research has shown that the cutting conveyance behavior of a spiral auger is highly dependent on its rotational speed n (Pang et al, 2023; Chen et al, 2018). When n is small, that is, the generated centrifugal force is small, the friction between the cuttings and drilled borehole is not sufficient to convey the cuttings upward; therefore, the cuttings can merely rotate along with the auger flights (Zhang and Ding 2017).…”