Heat transfer medium for heat pipes and external hydraulic circuits of thermal control systems of unmanned and manned spacecraft

The paper states requirements for one-phase and two-phase heat-transfer agents for thermal control systems of spacecraft. It provides physical, chemical, thermal and operational properties of a number of thermal transfer agents based on hydrocarbons, organosilicone and perfluororganic liquids, and it also provides a rationale for selection of a series of thermal transfer agents. The paper provides results of studies of corrosive resistance of metallic materials exposed to a series of heat transfer agents and recommendations for selecting the fluid circuit material. A new thermal transfer agent is proposed for heat pipes and outside fluid circuits with a freezing point no higher than -100 °C. The practical relevance of this work has been validated by the successful use of the developed and studied heat transfer agents in thermal control systems of spacecraft.