Lunar rovers evolve to survive the harsh lunar night

With days of 260 degrees Fahrenheit followed by weeks of evenings dropping to negative 280 degrees, lunar explorers like Japan’s SLIM can only withstand so much environmental damage. But if humanity is to establish a permanent presence on the moon, astronauts will need more adaptable equipment in the long term – and researchers are developing innovative solutions to ensure tools like lunar rovers are up to the task. Existing lunar rover insulation systems generally use expensive heaters or lower efficiency passive valves attached to loop heat pipes (LHPs) for temperature control. To solve this problem, an engineering team from Nagoya University recently collaborated with the Japan Aerospace Exploration Agency (JAXA) to design a medium heat switch device that oscillates between cooling and warming the electronic equipment aboard a lunar rover . Their prototype, detailed in the journal Applied Thermal Engineering, combines an LHP with an electrohydrodynamic (EHD) pump to create an incredibly efficient, low-power device that is equal parts a refrigerator and a laptop cooling system. [Related: Wild NASA proposal envisions magnetic hover trains on the moon.] Masahito Nishikawara, co-author and lead researcher on the paper, called such heat switch technology “essential for long-term lunar exploration” in an accompanying announcement earlier this month. “During the day, the lunar rover is active and the electronic equipment generates heat. Because there is no air in the room, the heat generated by the electronics must be actively cooled and dissipated,” says Nishikawara. “On the other hand, electronics need to be insulated from the outside environment during extremely cold nights so that it does not get too cold.” To address these hurdles, the team’s new thermal control device first relies on a phase-shift coolant in the LHP during scorching hot Mondays. As the liquid evaporates, its associated heat is released through a rover’s radiator – a process that repeats after the coolant cools and condenses back into a liquid. During moon nights, the EHD pump is turned on to generate an electrical current through the fluid. This creates a magnetic field that exerts enough pressure to block the movement of the coolant in the LHP. In addition, the rover’s electronics remain completely insulated from freezing temperatures, while consuming only small amounts of energy. “This groundbreaking approach not only ensures the rover’s survival in extreme temperatures, but also minimizes energy consumption, a crucial consideration in the resource-constrained lunar environment,” Nishikawara explains. “It lays the foundation for possible integration into future lunar missions and contributes to the realization of sustainable lunar exploration efforts.” The new system likely won’t be limited to lunar rovers. In the future, similar thermal switches will find their way into larger transportation vehicles and spacecraft, providing astronauts, and not just machines, with crucial protection.