Effects of Regolith Shielding on the Three-Dimensional Temperature Distribution of Lunar Habitat Structure

Abstract This study presents a comprehensive methodology for determining temperature distributions inside a regolith-shielded dome-shaped lunar habitat structure. The three-dimensional heat diffusion equation in a spherical coordinate system was discretized using the explicit finite-difference method incorporating appropriate boundary conditions. The heat inputs on the structure included direct solar irradiation and lunar regolith albedo, while heat outputs comprised nonblackbody radiation with deep space and habitat albedo. The structural self-shadowing, as well as the shadow effect on the surrounding lunar regolith, were integrated into the temperature analysis to enhance its realism. The habitat structure was constructed using sintered lunar regolith simulant. Appropriate available thermophysical properties were assigned to the habitat wall structure and regolith protection cover, with the latter exhibiting temperature-dependent material properties. The temperature on the external surface of the habitat structure, critical for maintaining structural integrity and internal thermal stability, was evaluated for regolith thicknesses ranging from 0 cm (no cover) to 20 cm at selected points on the dome structure. The analysis revealed substantial diurnal temperature fluctuations on the outer surface of the regolith protection cover, ranging from the maximum value of approximately 395.5 K (122.4°C) during the day to the minimum value of 106 K ( − 167.1 ° C ) at night. Without the regolith cover, the dome apex surface exhibited the maximum temperature of 394.5 K (121.4°C) and the minimum temperature of 213.5 K ( − 59.7 ° C ), resulting in the extreme diurnal temperature fluctuation of 181 K (181°C). Even a thin 2 cm thick regolith cover substantially mitigated these extremes at the outer surface of the habitat structure, reducing the diurnal temperature fluctuations to as low as 56.5 K (56.5°C), with the maximum of 324.5 K (51.4°C) and the minimum of 268 K ( − 5.1 ° C ). With the 20 cm thick regolith cover, the maximum and minimum temperature values at the habitat outer surface were observed to be 294 K (20.9°C) and 290.5 K (17.3°C), respectively, leading to the diurnal fluctuation of only 3.5 K (3.5°C), highlighting the cover’s excellent thermal insulation. These findings are necessary for determining the optimal regolith cover thickness required to protect the habitat structure from extreme temperature limits, as well as for evaluating the structural responses, such as stresses and deflections, needed for the design of safe and resilient lunar habitat structures.