Oxygen production from lunar raw materials is critical for sustaining a manned lunar base but is very power intensive. Solar concentrators are a well-researched and developed technology for harnessing the sun's energy to heat regolith to high temperatures (over 1273K). 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 differences between rigid and flexible concentrators are also compared. Possible substrate elements for a rigid mirror concentrator are chosen and discussed, with the following criteria: low CTE, high modulus of elasticity, and low density. Possible lunar locations for concentrator technology are also compared and contrasted. Several environmental and processing-related challenges related to dust and optical surfaces are addressed. This paper also examines the various sources of thermal energy that can be utilized for ISRU applications on the lunar surface. These include heat from nuclear and electric sources and solar concentrators. The options for collecting and transporting the heat to the processing reactor for each source are examined. The overall system requirements for each thermal source are compared and the system limitations, such as maximum achievable temperature are discussed.

A heat pipe radiator trade study has been completed for radiators in the 300-550 K temperature range. Initially, a thorough component level study was completed to determine heat pipe operating properties over the temperature range, particularly at the high end where the Merit Number starts fall off. Heat pipe designs for different dimensions were developed, and the maximum heat pipe power was determined. A trade study was then conducted that varied heat pipe O.D., evaporator length, heat pipe length, temperature, heat pipe spacing, fin thickness, and fin thermal conductivity. The radiator design that maximized specific power is shown, as well as the variation in mass with heat pipe spacing. RADIATOR PANEL DESIGNThe overall radiator panel layout is shown in Figure 1. The panel has the following: 1. A series of titanium/water heat pipes to transfer heat from the secondary fluid to the radiator panel 2. High conductivity graphite foam saddles to form an interface between the circular heat pipe and the flat fin 3. High conductivity Graphite Fiber Reinforced Composites (GFRC) fins 4. Aluminum honeycomb to provide stiffness to the structure The heat pipe configuration assumes that a series of round heat pipes (with integral saddles) are embedded in the radiator panel to distribute heat. The thermally active part of the radiator panel uses high-temperature-capable Graphite Fiber Reinforced Composites (GFRC's). This is a polymer matrix material, which we feel represents a

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