Feasibility study of a cryogenic heat switch based on shape memory alloy actuation

This works aims at carrying out a preliminary design of a Cryogenic Heat Switch capable of meeting the mission requirements for Infra-Red detector cooling at an operational temperature range of 30-80 K. The current development in space missions saw usage of high resolution IR detectors for military and astronomical observations. But these detectors require cryogenic cooling to cut-off thermal noises. At cryogenic subsystem level one of the mission critical issue is robustness to Single Point Failure which can be achieved through redundant systems. For thermal linkage of redundant systems to the detector we need an efficient heat switch operating at cryogenic temperatures. Initially literature review was carried out to analyze IR detectors, cryocoolers and various type of heat switches. Shape Memory Alloy (SMA) based heat switch was one of the best options because of the following advantages (i) can recover large strains up to 8% and can occur against large forces (ii) integrates both sensory and actuation functions therefore less complex (iii) exhibits superior thermal isolation in open states. Various material combinations were analyzed and their properties at cryogenic temperatures. Thermal analysis were carried out to verify they meet the design requirements.