Impact of Lunar Surface Features on the Core Temperatures of Surface-Crafts

Abstract

This work focused on modeling the transient thermal behavior of objects on the surface of the Moon. We determined the impact of the lunar environment, such as latitude, craters, boulders, and slopes, on the core temperatures of specific objects. In particular, we investigated a human in an EVA-suit, an exploration rover, and a highly integrated spacecraft. Internal parameters affecting the core temperature of the investigated objects are: body density, heat capacity, insulation, and internal power load level. The lunar geometry was modeled with the Thermal Moon Simulator (TherMoS) tool and the simulations were carried out with ESATAN-TMS. TherMoS is a tool currently under development to fill the gap in dynamic modeling of the thermal behavior of moving bodies on the lunar surface. The specific objects were modeled as generic spacecrafts without active thermal control. This model approach emphasizes temperature fluctuations at the expense of realism. The results of the semi-dynamic approach used in this paper, for non-actively controlled spacecraft, show that latitude and craters have the highest impact on sample body core temperatures (ΔT from 0 to -100 K, and +30 to -65 K, respectively, between undisturbed case and obstructed case), followed by boulders and nearby slopes (ΔT delta temperatures of +15 to -55 K and +20 to -45 K, respectively). Internal thermal loads have a significant impact as well, especially in the case of astronauts in space-suits. Temperature differences caused by the environment are most pronounced in rovers with small thermal inertia. Compared to static calculations, the semi-dynamic approach used in this work allows for the calculation of temperature gradients. For the case of a human in an EVA-suit, the calculated core temperature rate of change varied in the range of -0.041 to +0.045 K·min 1 . From these values, the heat flux necessary to maintain a core temperature of 310 K ranged from -178 W (required power for heating) to +196 W (excess heat, to be removed). Based on these findings we discuss the limits of current static and semi-dynamic thermal design approaches and simulation tools with regard to transient effects in the border zone between sunlight and shaded regions.