Utilizing water ice from the lunar permanently shadowed regions (PSRs) is essential for sustainable space exploration. This study explored the optimization of thermal mining methods for in-situ water ice extraction, focusing on how to adjust the configuration of heating rods to meet the flexible operational needs on the Moon, alongside the effects of water ice particle size and heating temperature. Our findings suggest that optimizing the heating temperature according to the water ice particle size and arrangement of heating rods significantly improves extraction performance. Specifically, by maintaining the water ice particle size greater than 20 mu m, we increase the thermal conductivity of the regolith-ice mixture by approximately 135 % compared to dry regolith, greatly shortening the extraction time. Notably, precise control of extremely low heating temperatures allows for significant expansion of the extraction range of a single heating rod. In scenarios where time constraints are minimal, the extraction range can be significantly expanded. Our innovative approach, grounded in fundamental heat transfer principles, demonstrates broad applicability and potential extension to water ice extraction on other celestial bodies. These findings provide a crucial foundation for efficient lunar resource utilization, satisfying the critical needs of future lunar missions and advancing human presence on the Moon.

Lunar in-situ water ice utilization is considered an essential part of the future construction of Lunar Bases. However, the thermal conductivity of lunar regolith without water ice is extremely low, which seriously hinders the thermal mining of lunar water ice. In this study, we proposed a novel approach to optimize the energy ef-ficiency of water ice thermal mining. In this method, a constant temperature heat source with a heating tem-perature selected according to the particle size of water ice was used to slow down the reduction rate of the thermal conductivity of icy soil. Our simulation results showed that the relatively high mining temperature led to the rapid sublimation of water ice near the heat source, reducing the thermal conductivity of the icy soil and the energy efficiency.A relatively low mining temperature decreases the sublimation speed of water ice and reduces energy effi-ciency. The particle size of water ice determined the decreasing rate of thermal conductivity of icy soil, thus affecting its optimum heating temperature. Using a constant temperature heat source at the optimal heating temperature, the energy efficiency of water ice mining could be increased by several orders of magnitude compared with constant power heating.

It is of great significance to realize the in-situ utilization of lunar water ice for the establishment and sustainable operation of the future lunar base. Considering the location of water ice in the lunar polar regions, based on the in-situ thermal mining method, an integrated approach for the water ice recovery was established. The evolution characteristics of average temperature of the icy soil and water vapor collection rate with the mining time were analyzed. The optimal mining temperature for the recovery of water ice was studied. The energy efficiency under various arrangement densities of heating elements was assessed with the optimal number of heating elements determined. The results show that as the mining time increases, for different target mining temperatures, the average temperature of the icy soil rapidly rise at first, and then tend to stabilize. The water vapor collection rates at different target mining temperatures vary greatly due to the difference in saturated vapor pressure of water ice. At high mining temperatures, the sublimation coefficient also significantly affects the process of water vapor collection. The water vapor collection rate with sublimation coefficient being unity is up to 36% larger than that with non-constant sublimation coefficient for the lunar soil under investigation within four earth weeks at the target mining temperature of 240 K. In addition, the increase of the mining temperature increases the water vapor collection rate, and at the same time, the water vapor pressure in the capture tent also increases, which may lead to the instability of the water ice production system. Combining with water vapor collection rate and change rate of water vapor pressure in the capture tent, the temperature of 220 K is obtained as the optimal target mining temperature. Furthermore, for the lunar soil in this work, the energy efficiencies for water ice production with seven and nine heating elements are same, and greater than that with five heating elements. Considering the energy efficiency, the minimum number of heating elements could be determined.