Thermal control is an important aspect of spacecraft design, particularly in the case of crewed vehicles, which must maintain a precise internal temperature at all times in spite of sometimes drastic variations in the external thermal environment and internal heat loads. The successes of the Space Shuttle and International Space Station programs have shown that this can be accomplished in Low Earth Orbit (LEO), however, crewed spacecraft traveling beyond LEO are expected to encounter more challenging thermal conditions with significant variations in both the heat rejection requirements and environment temperature. Such missions will require radiator systems with high turndown ratios, defined as the ratio between the maximum and minimum heat rejection rates achievable by the radiator system. Current radiators are only able to achieve turndown ratios of 3:1, far less than the 12:1 turndown ratio which is expected to be required on future missions. An innovative radiator concept, known as a morphing radiator, uses the temperature-induced shape change of shape memory alloy (SMA) materials to achieve a turndown ratio of at least 12:1. Predicting the thermal and structural behavior of SMA-based morphing radiators is challenging due to the presence of two-way thermomechanical coupling that has not been widely considered in the literature. Previous work has demonstrated the application of a technique known as a partitioned analysis procedure which can be used to simulate the behavior of morphing radiators. This work describes ongoing efforts to evaluate the physical accuracy of this approach by conducting validation studies. A detailed finite element model of a morphing radiator is developed and executed using the framework. Preliminary results show close agreement between the experimental data and model predictions, giving additional confidence in the partitioned approach.
Thermal control is an important aspect of every spacecraft. The thermal control system (TCS) must maintain
the temperature of all other systems within acceptable limits in spite of changes in environmental conditions or
heat loads. Most thermal control systems used in crewed vehicles use a two-fluid-loop architecture in order to
achieve the flexibility demanded by the mission. The two-loop architecture provides sufficient performance, but
it does so at the cost of additional mass. A recently-proposed radiator concept known as a morphing radiator
employs shape memory alloys in order to achieve the performance necessary to use a single-loop TCS architecture.
However, modeling the behavior of morphing radiators is challenging due to the presence of a unique and complex
thermomechanical coupling. In this work, a partitioned analysis procedure is implemented with existing finite
element solvers in order to explore the behavior of a possible shape memory alloy-based morphing radiator in a
mission-like thermal environment. The results help confirm the theory of operation and demonstrate the ability
of this method to support the design and development of future morphing radiators.