Experimental Characterization of a Composite Morphing Radiator Prototype in a Relevant Thermal Environment

Abstract

For future long duration space missions, crewed vehicles will require advanced thermal control systems to maintain a desired internal environment temperature in spite of a large range of internal and external heat loads. Current radiators are only able to achieve turndown ratios (i.e. the ratio between the radiator's maximum and minimum heat rejection rates) of approximately 3:1. Upcoming missions will require radiators capable of 12:1 turndown ratios. A radiator with the ability to alter shape could significantly increase turndown capacity. Shape memory alloys (SMAs) offer promising qualities for this endeavor, namely their temperature-dependent phase change and capacity for work. In 2015, the first ever morphing radiator prototype was constructed in which SMA actuators passively altered the radiator shape in response to a thermal load. This work describes a follow-on endeavor to demonstrate a similar concept using highly thermally conductive composite materials. Numerous versions of this new concept were tested in a thermal vacuum environment and successfully demonstrated morphing behavior and variable heat rejection, achieving a turndown ratio of 4.84:1. A summary of these thermal experiments and their results are provided herein.

Fabrication and Characterization of a Shape Memory Alloy Driven Composite Morphing Radiator Prototype

“…Previous works investigated using stainless steel foil adhered to thermal graphite sheets with SMA wires [6], a thermally conductive copper panel with SMA wires [7], and a composite facesheet with SMA strips [8]. This present work extends the development of the radiator prototype by using a carbon fiber composite facesheet, two different SMAs tailored to the lunar environment, and expanding operation to a five-panel serial subsystem.…”