Recovery rate prediction in lunar regolith simulant drilling

Drilling and coring, as an effective way to acquire lunar regolith along the depth, is widely used in the field of planetary explorations. Because there is no relative sliding between the lunar regolith and the flexible tube, using the flexible tube coring method can acquire high recovery rate and keep the stratification of regolith samples. Very little work has been done to analyze the flexible tube coring process. A proper understanding of the coring process is necessary to develop the drilling strategy and verify whether the designed drill tool is appropriate. In this paper, two models are developed to analyze stress distribution in lunar regolith simulant during coring. Based on the developed models, a prediction method of recovery rate is developed to analyze the influence of the drilling parameters on the recovery rate. Comparison of the model calculation results with data of drilling and coring experiments demonstrated that the model based on the Terzaghi bearing theory can effectively predict the tendency when the recovery rate begins to decrease.