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

Abstract

The extreme environment of deep space requires thermal control capable of maintaining safe temperatures within the spacecraft. In the vacuum of space, radiation is the dominant heat transfer mechanism for rejecting waste heat. Radiators incorporated within a thermal control system (TCS) enable temperature adjustments to the TCS working fluid loop. Shape adaptive morphing radiators control the TCS working fluid temperature partially through radiator geometry modifications, enabling variable heat rejection capabilities and possibly eliminating the need for multiple fluid loops, therefore decreasing system mass. The 2015 NASA Technology Roadmap dictates that the ratio between the maximum and minimum heat rejection, known as the turndown ratio, be at least 6:1 to manage changing thermal requirements between low Earth orbit, interplanetary travel, and lunar surface operations. Components formed from shape memory alloys (SMAs) change shape in response to a thermal stimulus. In this work, SMA wires are wrapped around an open cylindrical conductive composite shell and are conductively coupled to coolant passages, providing thermally responsive actuation that opens and closes the composite radiator at design temperatures. The carbon fiber radiator facesheet optimizes both thermal conductivity and stiffness properties, allowing for enhanced thermal and structural performance, respectively. The SMA wire transformation temperatures and actuation properties are tailored to the requirements of a specific mission, and heat rejection adaptability is demonstrated. While past prototypes have proven concept feasibility in a relevant thermal environment, this work considers the most high-performance and carefully designed morphing radiator to date increasing the technology readiness level (TRL) to TRL 5.