Modeling, Simulation and Comparison of Lunar Thermal Water Extraction Methods for Space Resource Utilization

Abstract

In-situ Resource Utilization (ISRU) is considered to be the key to consistent and sustainable human space exploration. Especially water is one of the most essential resources since it can be used for both life support and rocket fuel production. For that, is important to know what methods are most suitable to obtain water and what parameters may influence the extraction process. This work covers the simulation and comparison of three different thermal water extraction methods: 1) in-situ surface heating, 2) heated drills, and 3) heating inside a crucible after excavation. A parameter study was conducted investigating the influence of varying icy deposits from 1 wt.% to 15 wt.% and power inputs of max. 2,5 kW on the average extraction rate and energy efficiency of the system. Given the low fidelity of the designs, the evaluation also includes criteria like lifetime, water ice accessibility, and complexity. In general, especially the low thermal conductivity of the regolith was shown as a major bottleneck for thermal extraction. Furthermore, the water content of the soil was determined to have the biggest impact on the yield by greatly influencing the thermophysical properties of the regolith. It was found that the crucible was the best-performing method due to being thermally insulated and a completely closed system reaching an average extraction rate of up to ~ 0,9 kg/h for an optimized heating time (surface heating: ~ 0,09 kg/h; heated rods: ~ 0,32 kg/h). Yet, the design has downsides regarding the lifetime and complexity compared to both surface heating and heating via drills, which need to be considered for individual mission objectives.