Deployable, Lightweight, Freeze-Tolerant Radiator For Two Phase Thermal Management

Future space exploration missions require advanced thermal control systems (TCS) to dissipate heat from spacecraft, rovers, or habitats to external environments. These TCSs must be lightweight, reliable, and able to effectively control cabin and equipment temperatures under widely varying heat loads and ambient temperatures. In contrast to single‑phase pumped coolant loops, two‑phase pumped loops are very attractive for this application because of the uniform cooling temperature provided by the boiling coolant, low required pumping power, high‑heat transfer coefficients, and high thermal conductance. Introduction of two‑phase flow can pose design challenges associated with flow management and dynamic stability. A deployable condensing radiator technology is needed to enable future heat rejection systems with high turndown ratio, compatibility with freezing, while balancing considerations unique to two‑phase flow condensation. Creare has developed a freeze‑tolerant, variable‑conductance radiator for deployable heat rejection in two‑phase pumped loop systems. In Phasenbsp;I, we proved the feasibility of the concept by developing a preliminary design for the inlet header and phase separator, then fabricating a breadboard condensing radiator to demonstrate its performance. In parallel, we developed a novel process for fabrication of high permeability metallic porous tube elements, and we demonstrated its favorable properties through testing in two-phase anhydrous ammonia. We then finalized the thermal, fluid, structural, and mechanical design of the integrated condensing radiator with deployment features. Our overall design meets all requirements as defined in the solicitation including mass (lt;8 kg/m2), radiation tolerance, high-turndown freeze-tolerance (200:1), and ammonia compatibility. In Phasenbsp;II, we fabricate a prototype deployable radiator and demonstrate its performance in a representative thermal environment within a two-phase pumped ammonia loop.