Passive, Durable, Gravity-independent Condensing Heat Exchangers for PLSSs

We propose a 3D-printed, light, durable, passive, gravity-independent condensing heat exchanger (CHX) to meet the rigorous requirements of EVAs in long-duration space exploration missions. The proposed 3D-printed CHX relies on an innovative dual-plane gradient wick structure combining in- and out-of-plane capillary action to capture, collect, and recover the humidity exhaled and perspired by astronauts during EVAs. Unlike current condensers that share a common surface for both droplet nucleation/growth and condensate removal, the out-of-plane gradient wick decouples the nucleation/growth surface from the condensate removal for enhanced humidity condensation and delayed flooding. The in-plane gradient wick then directionally and passively transports the condensed humidity to a capillary reservoir for later drainage upon completion of the EVA. This enables full passive condensate management by preventing flooding and ensuring efficient removal to a reservoir. Previously, we successfully demonstrated the concept of the in-plane gradient wick condenser for enhanced flow condensation of pure dielectric/refrigerant vapors (i.e., no air). Building on this experience, the proposed project conceptualizes and demonstrates a novel dual-plane gradient wick topology for varied g-fields. Phase I deliverables will include: 1. Detailed modeling and simulation results demonstrating the optimal pore size distribution of the dual-plane gradient wick structure will be delivered. 2. A functional prototype of the proposed dual-plane gradient wick CHX complemented with detailed design documents will be delivered. 3. Detailed experimental results demonstrating that the proposed dual-plane gradient wick CHX meets the project’s performance metrics will be delivered. 4. A detailed design for a full-scale dual-plane gradient wick CHX will be delivered. Also, a detailed assessment of its potential integration into future PLSSs for lunar and Martian missions will be conducted.