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Hydrogel for Transpiration Cooling

Company: The Johns Hopkins University Applied Physics Laboratory

Primary: ME
Secondary: MATSE
Optional: ESC, IE

Non-Disclosure Agreement: NO

Intellectual Property: NO

NEED Transpiration cooling is achieved by moving a liquid or gas coolant through a hot structure to absorb and eject a portion of the heat by evaporation through a porous skin. This highly effective cooling technique has been theoretically investigated and demonstrated in experimental and operational settings. For example, SpaceX successfully employed transpiration cooling in their reusable second stage rocket motors and spacecraft to mitigate the harsh conditions of reentry. Transpiration cooling systems typically consist of a porous skin, coolant tank, coolant channels, a pump, and control systems. These complex systems are feasible for large vehicles but may become impractical for smaller vehicles or subsystems due to weight and size restrictions. Therefore, there is an urgent need for the development of a “low profile” and practical transpiration cooling technique that is suitable for smaller vehicles, especially when only transient (seconds) or short term (tens of seconds) of cooling is needed. CONCEPT Investigate the potential for a fiber reinforced thermal management concept based on hydrogel structures for transpiration cooling. Hydrogels are three-dimensional polymer network structures able to absorb large amounts of water to form a “solid” form of water, especially when reinforced with a porous solid scaffold. Structurally (metal lattice) reinforced hydrogels can be engineered to release a phase changing cooling medium to reduce surface temperatures during most thermally aggressive operations while maintaining shape stability. Such designs will significantly reduce the footprint of the transpiration cooling system by eliminating the need for pumping and control systems. PROJECT DESCRIPTION The main tasks include: 1. Use thermal and mass simulation tools to design, analyze, and evaluate a “self-pumping” transpiration cooling system based on embedded hydrogel coolant 2. Fabricate a representative test coupon by metal additive manufacturing 3. Test the cooling effectiveness with a high velocity oxygen fuel system (to be done at JHU/APL). 4. Improve both theoretical and experimental designs of the hydrogel based transpiration system by examining the test results.