Abstract:

Drilling and coring is adopted as an effective method for acquiring deep sample by the autonomous sampling mission in the third phase of China lunar exploration. Since the mechanical properties of different lunar regolith components are distinct and the components in longitudinal direction are distributed randomly, the drilling loads may fluctuate heavily, affecting the stability of drilling process. To secure the sampling mission, the drilling device should be adjusted to suitable drilling parameters promptly and control the drilling loads online under limited drilling power and weight of bit. The failure mode and conveyance of lunar regolith under the effect of drill tool are analyzed and a new concept of filling rate of auger flute (FRAF) is proposed to describe the auger’s conveyance in quantity. Based on the screw conveyance theory, a drilling load model under two conventional drilling conditions is established. Experiments in lunar regolith simulant under multi-dimension drilling parameters on the ground indicate that FRAF index reflects accurately the cuttings removal and this drilling load model estimates the drilling loads well.

Key words: drilling loads, drilling parameters, filling rate of auger flute, lunar drilling and coring