Development of a Flexible Thermal Control Device with High-Thermal-Conductivity Graphite Sheets

This paper describes a new passive thermal control device-a Reversible Thermal Panel (RTP)-which changes its function reversibly from a radiator to a solar absorber by deploying/stowing the radiator/absorber reversible fin. The RTP consists of Highly Oriented Graphite Sheets (HOGSs), which have characteristics of high thermal conductivity, flexibility and light weight, as thermal transport units, which can transport the heat from equipment to reversible fin, and of a Shape - Memory Alloy (SMA) as a passively rotary actuator to deploy/stow the reversible fin. The RTP prototype model was designed and fabricated using HOGSs, a honeycomb base palate, and a prototype reversible rotary actuator. The heat rejection performance of the RTP as a radiator and the heat absorption performance as an absorber were evaluated by thermal vacuum tests and thermal analyses. The autonomous thermal controllability achieved using the prototype rotary actuator was also evaluated. The test results showed that RTP gave an excellent performance as a passive radiator from the standpoints of heat rejection capability, specific heat rejection, and variation of the radiator fin efficiency. The effectiveness of the RTP as a solar absorber that can be substituted for a survival heater was also confirmed. The necessity of reinvestigating the thermal conductance between the equipment simulator plate and the rotary actuator housing, and of designing a reversible rotary actuator using a shape-memory alloy to achieve higher deployment torque, were revealed.