Towards High Turndown Ratio Shape Memory Alloy-Driven Morphing Radiators

Future manned space missions will require thermal control systems that can adapt to larger fluctuations in temperature and heat flux that exceed the capabilities of current state-of-the-art systems. These missions will demand novel space radiators that can vary the heat rejection rate of the system to maintain the crew cabin at habitable temperatures throughout the entire mission. Current systems can provide a turndown ratio (defined as the ratio of maximum to minimum heat rejection) of 3:1 under adverse conditions. However, future missions are projected to demand thermal control systems that can provide a turndown ratio of more than 6:1. A novel radiator concept, known as the morphing radiator, varies the system heat rejection rate by altering the shape of the radiator that is exposed to space. This shape change is accomplished through the use of shape memory alloys, a class of active materials that exhibit thermomechanically-driven phase transformations and can be used as both sensors and actuators in thermal control applications. In past efforts, prototype morphing radiators have been tested in a relevant thermal environment, demonstrating the feasibility and scalability of the concept. This work summarizes the progress towards testing a high-performance morphing radiator in a relevant thermal environment and details the development of an efficient numerical model that predicts the mechanical response of an arbitrary morphing radiator configuration due to changes in temperature. Model predictions are then validated against previous experimental results, demonstrating the usefulness of the model as a design tool for future morphing radiator prototypes.