LuNaDrone, nano drone for Lunar pits exploration: Thermal Analysis and Thermal Control System preliminary design

Following the Artemis Accords signed by Italy and the United States in 2020, a new line of mission proposals was born, focused on NASA's prospects for lunar exploration. The goal of the latter is no longer limited to the return of humans to the Moon but aims to the development of technologies and knowledge necessary to enable long-term or permanent human presence on our natural satellite, with an eye to the future and human exploration of Mars. Italy's role, emphasized in the Accords, is to contribute to the development of enabling technologies for lunar surface exploration. In this light, the Lunar Nano Drone (LuNaDrone) mission concept was conceived. LuNaDrone aims to explore possible lunar lava tube entrances, with the triple purpose of assessing the presence of said geological structures, evaluating the feasibility of establishing lunar outposts, and acquiring scientifically relevant data about lunar geology. The mission is carried out via an autonomous small spacecraft, transported to the lunar surface by a host spacecraft. To provide a flexible and low-cost solution for lunar exploration, the concept follows the CubeSat standardization and modularity approach, leading to a product compatible with development in an academic environment. The LuNaDrone project has been ongoing since 2020, led by Politecnico di Torino with the involvement of selected Italian SMEs, and is now entering the prototype phase with the development of the drone’s main systems. Access to these underground features, proposed in the past by NASA, ESA and JAXA as promising sites for human settlement due to their favourable environment (protection from temperature extremes, radiation, and micrometeoroids), might be possible through certain lunar pits, points where the ceiling of the lava tubes could have collapsed. The focus of this thesis is the assessment of the thermal environment in which the mission will operate, a first thermal analysis of the drone under these conditions and the design of a preliminary thermal control system. First, an up-to-date introduction to lunar lava tubes and pits and a description of the LuNaDrone concept are presented. Then, the drone in its February 2023 configuration is described and characterised in its principal components, defining its thermal budget together with its main geometric, physical, and optical characteristics. Following these introductory sections, the thermal problem is presented, along with a description of the mathematical models underlying the thermal analysis. The thermal environment encountered during the mission is discussed, with a focus on the surface phases. Model construction and thermal analysis were conducted through commercial software, Thermal Desktop by Cullimore&Ring Technology, and SINDA/FLUINT solver. Given the criticality of the thermal design in a hostile environment such as the lunar one, it was decided to focus the study on the mission phases not supported by the host spacecraft, i.e. ground and operational phases. A thermal model of the lunar surface was constructed and validated with data from Apollo 17; similarly, a lunar pit was modelled and validated with data from the Diviner mission. Thermal analyses of the above-mentioned phases were conducted, highlighting the mission's thermal criticalities. Finally, based on the state of the art of thermal control in small spacecraft, a preliminary design of the thermal control system was proposed.