LAUSR

Abstract In lunar soil drilling, stones have significant influences on sampling. Herein, stones are classified into greater stones and supramaximal stones based on their sizes. Five simulation conditions with different sizes and positions of the stone were designed. The stone trajectories, sampling efficiencies, velocity field, stress field and load curves were compared and analyzed. The results indicated that the resultant axial force and torque were mainly decided by the load of the bit. The stone affected the stress of the particles around it obviously, but had little effect on the velocity field. A greater stone, having diameter smaller than that of the virtual cutting circle of the drill bit, has little influence on the lunar soil drilling process. However, a supramaximal stone, with diameter larger than that of the virtual cutting circle, significantly affects the lunar soil drilling process. If supramaximal stones are near the edge of the virtual cutting circle, they are easily spun out and can cause obvious discrete pulse peaks of axial force. If the supramaximal stones are screwed inward, they can easily cause a jam in front of the drill bit, making the soil injection difficult. An experiment result verified the effect of the supramaximal stone.