Water Extraction from Lunar Simulants using Microwave Heating: A Pathway towards In Situ Resource Utilisation on the Moon

Cole, James (2024). Water Extraction from Lunar Simulants using Microwave Heating: A Pathway towards In Situ Resource Utilisation on the Moon. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.00097975

Abstract

Water is a vital resource for creating a sustainable human presence in the Solar System. The lunar poles are thought to contain vast quantities of water ice in Permanently Shadowed Regions (PSRs). Determining the most energy efficient technique for extracting the water will become important to future endeavours as energy resources may be limited in areas containing no sunlight. Microwave heating offers volumetric heating of lunar regolith and therefore may be effective at extracting water from icy regolith. This thesis presents the feasibility of using low power (250 W) microwave heating as a water extraction technique. Initial thermal modelling demonstrated how low power microwave heating can extract large quantities of water from icy regolith. Analogue icy regolith samples were developed using different simulants, water contents, and forms of ice. Real time mass loss from in situ analogue samples during microwave heating was measured using a bespoke Dynamic Mass Instrument (DMI). The impact of different sample properties such as mineralogical composition, water content, ice grain size, and the form of ice were investigated. In Diffuse Icy Regolith (DIR) samples, mineralogical composition had a negligible impact on water extraction rates. For a range of water contents in DIR samples, the ratio of water extracted compared to the initial water content remained constant until the saturation point. At saturation, the extraction rate decreased due to the formation of free regions of ice. For Granular Icy Regolith (GIR), it was found that a larger ice grain size led to higher and more discrete water extraction rates. Extraction differences between different forms of ice were explained using data from the DMI. The highest extraction efficiency through various experiments was found to be 0.032 g/Wh in 25 minutes. This thesis demonstrates that low power microwave heating is a viable solution for water extraction from icy lunar regolith.

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