Jukyoung SHIN, Junhyeon BAE, Tae Young KIM
DOI Number: N/A
Conference number: HiSST-2025-047
Vehicles undergoing atmospheric reentry and hypersonic flight are exposed to severe aerodynamic heating that exceeds the capabilities of conventional passive thermal protection systems. Transpiration cooling, which delivers coolant through a porous medium to absorb heat and establish a protective fluid barrier, offers high thermal efficiency relative to coolant mass and is therefore a promising solution for reusable aerospace vehicles. In this study, porous Hastelloy X specimens were fabricated by slurry-based compaction and sintering under applied pressures ranging from 0 to 81 MPa to examine how processing conditions affect pore structure and cooling performance under high-enthalpy heating.
Porosity and permeability measurements showed that increasing compaction pressure reduced both total and open porosity, producing an overall ~60% decline in permeability due to diminished connectivity of flow pathways. Transpiration cooling experiments under a heat flux of ~1 MW/m² revealed that higher-pressure specimens maintained lower surface temperatures, demonstrating improved coolant utilization and enhanced thermal protection. These benefits, however, were offset by substantially greater hydraulic resistance, with the most compacted specimen exhibiting more than twice the pressure drop of the uncompressed sample. The results establish a fundamental trade-off: densification improves cooling uniformity and effectiveness but restricts fluid transport. This study provides quantitative design guidelines for optimizing porosity, permeability, and compaction pressure
to balance thermal performance with hydraulic losses, supporting the development of next-generation transpiration cooling systems for hypersonic and reentry vehicles.