Thermal Shielding of a Reentry Vehicle by Ultra-High-Tempreature Ceramic Materials

Reentry vehicles with enhanced aerodynamic performances and high maneuverability require sharp leading edges for the wings and control surfaces and a sharp tip of the fuselage nose where high localized heat fluxes occur. Ultra-high-temperature ceramics, for example, zirconium, hafnium, or titanium diborides, are candidate materials for the sharp edges of reentry vehicles that make use of new thermal protection systems, positioning massive thermal protection systems only at the leading edge of the wings (or at the fuselage tip). The boundary-layer thermal protection concept is illustrated, and the requirements for the geometry and materials of the fuselage nose are identified. It is shown how a sharp nose will protect the fuselage, acting as a lightning rod for the rest of the structure when the vehicle flies at relatively low angles of attack. Systematic numerical analyses are shown for the sphere-cone nose vehicle to compute temperature distributions along the surface and inside the nose structure at different angles of attack. The effects of the chemistry and of the surface catalysis are discussed.