A Variable-View-Factor Two-Phase Radiator Manufactured Via Ultrasonic Welding

Radiators for manned spacecraft, satellites, planetary rovers and unmanned spacecraft are typically sized for the highest power at the hottest sink conditions, so they are oversized and prone to freezing at low sink temperatures. In order to address the need for light-weight, deployable and efficient radiators capable of passive thermal control and a significant heat rejection turndown ratio, Advanced Cooling Technologies, Inc. (ACT) has developed a novel vapor-pressure-driven variable-view-factor and deployable radiator that passively operates with variable geometry (i.e., view factor). The device utilizes two-phase heat transfer and novel geometric features that passively (and reversibly) adjust the view factor in response to the internal vapor pressure in the radiator. The variable-view-factor two-phase radiator (VVFTPR) consists of hollow curved and straight panels, filled with a two-phase fluid. An increase in internal vapor-pressure, due to an increase in fluid temperature, results in elastic bending of the curved panel and an increase in view-factor. In addition, since the radiator is a two-phase device, its efficiency will approach unity.

Through a collaboration with the Edison Welding Institute (EWI), ACT has determined that the best strategy for manufacturing the VVFTPR is to use ultrasonic welding and Aluminum 7075 as the envelope material. This paper will present experimental results characterizing the performance of several prototypes constructed using ultrasonic welding. Prototypes will include an internal wick for liquid return, but a new wickless concept for the VVFTPR will be also be introduced and experimentally tested.

This work has been performed under NASA Small Business Innovation Research (SBIR) Phase II contract 80NSSC18P2187.