Thermal Shielding of a Reentry Vehicle by Ultra-High-Tempreature Ceramic Materials
ABSTRACT 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.
- SourceAvailable from: Rimantas LevinskasMaterials Science 04/2011; DOI:10.5755/j01.ms.17.4.781 · 0.34 Impact Factor
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ABSTRACT: In high temperature environments, molecular vibration and rotation become considerable in flow analysis. We employed unsteady direct simulation Monte Carlo to thoroughly investigate the effects of molecular vibration and rotation on the dynamic response of wall heat flux due to the oscillating flow input in a rarefied environment with high temperature. Three modes of temperature and heat flux (translational, vibrational and rotational) are distinctively quantified to identify the details of the response, in addition to the density and velocity fluctuations. With an increase in the medium temperature, the contribution of internal energy to the heat flux is found to significantly increase; however, the responses vary with the characteristic time of each mode. Besides their usefulness in contributing to the rapid development of space applications, the findings are expected to be significant in designing a thermal protection system for space vehicles in the future.Journal of Mechanical Science and Technology 03/2015; 29(3):909-916. DOI:10.1007/s12206-015-0204-0 · 0.70 Impact Factor
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ABSTRACT: The transition from blunt leading edges to sharp leading edges on re-entry aircrafts is necessary to increase both maneuverability and safety. However, the oxidation resistance of current materials is inadequate for the extreme conditions experienced by sharp leading edge re-entry vehicles. The Mo–Si–B alloy system has been utilized to design a multilayer coating that has the ability to protect from 800 to 1700 °C. Substrates of Mo and ZrB2–50 vol% SiC with a flat profile were coated with the Mo–Si–B based coating and evaluated using arc jet testing performed at NASA Langley Research Center. Heat fluxes of 2.5 to nearly 3.5 MW/m2 and surface temperatures of 1500–1650 °C were achieved during the 20-min tests. The samples presented in this study showed <3% mass loss and retention of sample shape and integrity, demonstrating the robust environmental protection under a simulated hypersonic environment offered by the Mo–Si–B based coating on refractory metals and ceramics.Journal of the European Ceramic Society 12/2014; 34(15):3521–3533. DOI:10.1016/j.jeurceramsoc.2014.06.011 · 2.31 Impact Factor