Overview of Technology Development of Shape Memory Alloy Morphing Radiators for Crewed Space Exploration Vehicles
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Upcoming crewed space missions will require management of large internal and external heat loads, necessitating advanced thermal control systems to maintain a desired internal environment. Radiators with at least 6:1 turndown ratios (the ratio between the maximum and minimum heat rejection rates) will be needed; however, current technologies are only able to achieve turndown ratios of approximately 3:1. A morphing radiator capable of altering shape and the configuration of exposed surfaces could significantly increase turndown capabilities. Shape memory alloys (SMAs) offer qualities that may be well-suited for this endeavor; their temperature-dependent phase changes offer radiators the ability to passively control heat rejection. This paper presents an overview of recent technology development of shape memory alloy-based morphing radiators for crewed spacecraft, beginning with a description of the initial concept formulation and both analytical and experimental proof-of-concept studies which demonstrated the feasibility of the morphing radiator concept. Subsequently, a fully functional morphing radiator prototype was constructed and tested in a thermal vacuum chamber, where it successfully demonstrated the morphing behavior and variable heat rejection in a simulated mission environment. Newer prototypes incorporating highly thermally conductive composite materials have more recently been designed and manufactured using two distinct types of SMA materials. These prototypes also underwent temperature cycling tests in a thermal vacuum chamber and a series of fatigue tests to characterize the lifespan of the design. Future work will focus primarily on integrating the morphing radiator with the rest of the thermal control system with the goal of developing system-level prototypes which could be incorporated into a spacecraft in place of a traditional radiator system.