# Design of Man-Machine Synergic Lunar Coring Device and Its Coring Dynamic Analysis
## 2 Process Analysis of Coring  
Currently, there are two methods to obtain lunar regolith samples with stratigraphic information (information on the layering of soil or rock along the vertical direction): impact penetration and rotary drilling sampling. These two sampling methods have advantages and limitations in the lunar surface sampling process. Rotary drilling methods can be roughly divided into single-blade/double-blade spiral drill rod drilling, hollow drill tube drilling, and no-slippage double-tube soft bag drilling [7]. The single-blade/double-bladespiral drilling method (Figure 1a) has a solid rock-breaking ability and high drilling efficiency. However, this coring method completely loses the stratification of lunar regolith samples. The hollow drill tube drilling method (Figure 1b) has a solid rock-breaking ability and high sampling efficiency and can maintain a certain sample of stratigraphic information. However, the rotary motion of the drilling tube causes the sample particles near the inner wall of the drilling tube to mix up and cannot keep the in situ stratigraphic information well [29]. The no-slippage double-tube soft bag drilling method (Figure 1c) has a hollow drill tube with an embedded holding coring tube and an inward-flip soft bag. A soft bag can collect the sample without slippage during sampling, keeping the sample's stratification [30]. Nevertheless, the mechanism is more complex, and flexible soft bag winding on the small diameter cylinder is bound to squash the force, thus affecting the laminarity of the sample. In addition, during the common drilling and sampling process, the friction between the drilling tool and the lunar regolith and rock generates a large amount of heat, which affects the life of the drilling tool and the quality of the sample [27; 31; 32]. An in-depth study on the optimal design of drilling tools is needed. Compared with the rotary drilling sampling method, impact penetration coring has better retention of sample stratigraphic information. The impact penetration method is generally used to obtain lunar regolith samples by manually striking the thin-walled coring tube and making the tube penetrate downward continuously [33]. However, the frequency of manual striking is low, and the squeezing of lunar soil particles near the coring tube generates enormous contact stress. This leads to increased friction between the lunar soil particles and the surface of the coring tube, which increases energy consumption and hinders sample collection, as shown in Figure 2a. It is found that high-frequency dynamic impact can reduce the contact stress between the coring tube and lunar soil particles and drive the lunar soil particles on the surface of the coring tube to move toward the lunar surface. The use of coring tubes with an anisotropic frictional surface profile can further enhance the transport effect of lunar soil particles and thus improve the coring rate [34; 35]. The coring tube has wedge-shaped \"barbs\" on the inner and outer surfaces so that the lunar soil particles near the outer wall of the coring tube are discharged from the lunar surface. In contrast, those near the inner wall of the coring tube are transported upward, keeping the length of the sample consistent with the penetration length of the coring tube, as shown in Figure 2b. These two sampling methods have their respective advantages and limitations in the process of lunar surface sampling. This study combines impact penetration and rotary drilling to ensure a stable sampling process. When working on the lunar surface, the astronaut or lander provides the feed force for the coring device. Impact penetration sampling is used to maximize the original lunar soil stratigraphy information for sampling the lunar regolith layers. When sampling deeper layers or encountering hard lunar rocks, the astronaut can start the impact penetration module and the rotary module at the same time. The coring tube can be replaced by an auger drilling tube to realize the cutting and  
Figure 1: Rotary drilling method diagrams.