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.
Creare’s freeze-tolerant radiator is designed specifically to enable deployable heat rejection from space-borne and surface pumped loop systems. The technology would be applied to dissipate heat from spacecraft, rovers, or habitats to external environments. In addition to thermal control, this system could be used for heat rejection in power conversion cycles.
An active industry is developing around use of pumped-loop thermal control systems for satellite thermal management. Several large satellite manufacturers and integrators are working to develop and implement spaceborne thermal control loops for powerful telecommunications satellites seeking to reject >10 kW. These systems would require a condensing radiator similar to Creare’s proposed technology.