The Influence of Coatings on the Performance of Structural Heat Pipes for Hypersonic Leading Edges

Previous analyses have shown that refractory metallic leading edges are feasible for Mach 6-8 airbreathing hypersonic vehicles when integrated with a structural heat pipe. This article investigates the effects of a coating on the exterior surface for potential thermal and environmental protection. Two conclusions are found: (i) Adding a thermal barrier coating does not allow operation at higher Mach number because the characteristic temperature of the system is unaffected by its presence. Instead, large (adverse) temperature gradients are induced through the coating. (ii) Coatings required to protect against oxidation can be safely applied provided that they are thin (<= 0.1 mm) and have sufficiently high thermal conductivity (>= 5 W/mK).