Two-Phase Thermal Switching System for a Small, Extended Duration Lunar Surface Science Platform

This paper describes a novel thermal control system for the Warm Electronics Box (WEB) on board a small lunar surface lander intended to support science activities anywhere on the lunar surface for an extended duration of up to 6 years. Virtually all lander electronics, which collectively dissipate about 60 W in the reference mission, are contained within the WEB. These devices must be maintained below 323 K (with a goal of 303 K) during the nearly 15‐earth‐day lunar day, when surface temperatures can reach 390K, and above 263 K during the nearly 15‐earth‐day lunar night, when surface temperatures can reach 100 K. Because of the large temperature swing from lunar day‐to‐night, a novel thermal switching system was required that would be able to provide high conductance from the WEB to the radiator(s) during the hot lunar day and low (or negligible) conductance during the cold lunar night. The concept that was developed consists of ammonia variable conductance heat pipes (VCHPs) to collect heat from WEB com...