Variable View Factor Two-Phase Radiator

NASA’s Space Technology Mission Directorate (STMD) is investigating technologies for thermal control systems (TCS) in human spaceflight vehicles, such as variable geometry spacecraft radiator. The TCS in crewed vehicles must maintain a relatively constant environment temperature for a wide range of external thermal environments (low earth orbit, trans-planetary coast, and planetary surface operations). The sink temperature may vary from approximately 70 K to 230 K.Recent researches investigated and presented potential of heat rejection capability from the morphing composite / shape memory alloys (SMA) radiator. The SMA radiator employs such temperature dependent SMA materials to passively morph the radiator shape and thus adjust the rate of heat rejection to a wide range of vehicle requirements. Nonetheless, utilizing SMA materials faces many disadvantages, including low actuation frequency, sensitivity of material properties in fabrication, residual stress’s developed in thin films, and nonlinearity of actuation force.Advanced Cooling Technologies, Inc. (ACT) proposes to develop a novel vapor-pressure-driven variable view factor radiator as a thermal control system component for spacecraft. Similar to SMA radiator mechanism, the radiator folds into a tear drop shape to minimize the view factor when cold, and opens up to maximize the view factor when heated. However, the proposed device instead utilizes vapor pressure inside a hollow curved panel to change the shape of the radiator. In Phase I, a proof-of-concept two-phase vapor pressure driven morphing radiator prototype will be fabricated and tested. Test results will be used to validate a thermo-structural model, which will be employed to design the full-scale prototype.