Research and Development of Heat Switch for Future Space Missions

Abstract

A heat switch provides a thermal switching (high or low thermal conductance) as appropriate according to the thermal environment of a spacecraft. It has an advantage for a thermal control for lunar rover and planetary exploration spacecraft for which it is difficult to secure sufficient electrical power. A mechanical heat switch is being developed in our group for Japanese spacecraft including the lunar rover. Required on / off thermal conductances are 1 W/K and 10 mW/K respectively with lower than 5 cm of height as a goa1. The volume expansion of paraffin was introduced for the on / off mechanism according to the result of a trade-off study including feasibility, power and expected mass. The heat switch test model we fabricated has a mass of 660 g, height of 53 mm, and outer diameter of 62 mm. In our thermal performance test, the thermal conductance was 0.86 W/K when the switch was turned on and an on / off ratio exceeding 110 was measured. In this paper, a description of the heat switch, mission targets, conceptional design study and the thermal performance result of the test model are presented.