Development and Testing of a Lightweight Thermal Louver with Single Crystal Shape Memory Alloy

Abstract

Space probes need to respond to short-term changes in the thermal environment caused by sunshine and shade during orbit, as well as long-term changes in the thermal environment during interplanetary navigation, where the sun's distance changes significantly. Until now, it has been supported by thermal louvers that control the amount of heat radiation by opening/closing blades with low emissivity, and SRDs whose surface emissivity changes depending on the temperature of the material itself. However, it is difficult to mount it on a small space probe from the viewpoint of mass and heat dissipation performance. In this research, we proposed a Shape memory alloy Thermal Louver (STL). Since the conventional thermal louver uses a spring-shaped bimetal as the drive source, it has a large mass and it is necessary to control the bimetal temperature by the heater. On the other hand, STL is compact, lightweight, and has a high effective emissivity On/Off ratio by using a shape memory alloy. This device uses a reversible actuator as the drive source that combines a single crystal shape memory alloy (SCSMA) and a bias spring, which enables autonomous thermal control according to the temperature of the equipment. In addition, it is lightweight and simple because it consists only of an aluminum frame, blades, and reversible actuators. In this study, a 50W-class STL was design, fabricated and tested. The following tests and evaluation results will be described in the full paper. ?Operation test results of a reversible actuator that combines a SCSMA and bias springs ?Thermal vacuum test results of 50W-calss STL prototype ?Evaluation of STL thermal performance using a thermal analysis model and TVT results