Thermal Energy for Lunar In Situ Resource Utilization: Technical Challenges and Technology Opportunities

Oxygen production from lunar raw materials is critical for sustaining a manned lunar base but is very power intensive. Solar concentrators are a well-developed technology for harnessing the Sun s energy to heat regolith to high temperatures (over 1375 K). The high temperature and potential material incompatibilities present numerous technical challenges. This study compares and contrasts different solar concentrator designs that have been developed, such as Cassegrains, offset parabolas, compound parabolic concentrators, and secondary concentrators. Differences between concentrators made from lenses and mirrors, and between rigid and flexible concentrators are also discussed. Possible substrate elements for a rigid mirror concentrator are selected and then compared, using the following (target) criteria: (low) coefficient of thermal expansion, (high) modulus of elasticity, and (low) density. Several potential lunar locations for solar concentrators are compared; environmental and processing-related challenges related to dust and optical surfaces are addressed. This brief technology survey examines various sources of thermal energy that can be utilized for materials processing on the lunar surface. These include heat from nuclear or electric sources and solar concentrators. Options for collecting and transporting thermal energy to processing reactors for each source are examined. Overall system requirements for each thermal source are compared and system limitations, such as maximum achievable temperature are discussed.