Self-Healing Radiator Coolant Tubes for Spacecraft Thermal Control

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, tolerant of extreme conditions, and highly-reliable. The typical layout for a thermal control system includes a large-surface-area radiator for heat rejection, embedded with fluid-filled heat pipes or coolant tubes with actively flowing liquid. Because radiators necessarily have a large footprint with exposure to space, they are particularly susceptible to strikes by micrometeorite and orbital debris (MMOD). Tubes breached by MMOD will invariably discharge their coolant, rendering the TCS inoperable. In this context a particular need has emerged for self-healing coolant tubes for resilience to MMOD impact. To meet this challenge, Creare proposes a unique coolant tube containment design, for which a multi-layered tube wall contains a microporous metallic internal matrix filled with a liquid reactant. The reactant is selected to rapidly polymerize with exposure to the internal pressurized coolant as it escapes into the vacuum of space, passively self-sealing the breach and ensuring continued operation of the TCS. In Phase I, we will collaborate with self-healing materials experts to select, develop and evaluate a test matrix of polymer systems with the potential to provide passive self-healing with exposure to one or more typical radiator coolants. We will then conduct a demonstration of a self-healing coolant tube, using a subscale multi-layered tube and the selected reactants, to evaluate the overall approach. Finally, we will develop the overall thermal, fluid, structural, and mechanical design of an integrated radiator complete with advanced features for self-healing. In Phase II, we will build a prototype radiator with self-healing features, demonstrate its performance in a representative thermal environment, and deliver the completed unit to NASA.