A Lightweight Freeze-Tolerant Radiator for Extreme Environments

Future space exploration missions require advanced thermal control systems (TCSs) to dissipate heat from spacecraft, rovers, or habitats to external environments. These thermal control systems must be lightweight, reliable, and able to effectively control cabin and equipment temperatures under widely varying heat loads and ambient temperatures, including the extremes of lunar night. In this context a particular need has emerged for a heat rejection technology that is both freeze-tolerant and can operate with high turndown to permit TCS operation during extreme conditions by passively varying thermal resistance, as identified by NASA in SBIR Topic Z13.05: There are no [state-of-the-art thermal control techniques] that can vary the thermal resistance of a radiator or heat exchanger to temporarily eliminate or reduce heat rejection, but this capability is desired to enable freeze tolerance. To meet these requirements, Creare proposes a freeze‑tolerant, variable-conductance radiator for deployable heat rejection in single-phase pumped loop systems. During conditions of low thermal load, the radiator freezes its distal end allowing a limited inactive portion of the radiator to operate and to continue dissipating heat without flow blockage. In Phase I, we will prove the feasibility of the radiator concept by using bench scale tests to demonstrate the key design features for the radiator. We will then finalize the overall thermal, fluid, structural, and mechanical design of the integrated freeze-tolerant radiator complete with advanced features for micrometeorite protection and future integration with a deployment mechanism. In Phase II, we will build a prototype radiator, and demonstrate its performance in a representative thermal environment, and deliver the completed unit to NASA.