Experimental investigation of passive/active oxidation behavior of SiC based ceramic thermal protection materials exposed to high enthalpy plasma

The passive/active oxidation behavior of a CVD-SiC coated C/C-SiC thermal protection material of the hypersonic SpaceLiner vehicle is investigated experimentally. For the safety of spacecraft and its passengers, it is important to know whether the thermal protection system will experience passive/active oxidation during the vehicle's entry into Earth's atmosphere. Active oxidation can promote material loss whereas passive oxidation forms a protective film.The high enthalpy flight conditions of SpaceLiner vehicle are duplicated in VKI Plasmatron, where the samples are exposed to high enthalpy plasma and the surface temperatures increase up to 2800 K at various total pressure (2–20 kPa) conditions. Surface temperature profiles, visual characteristics, mass changes, emissivity, spectrometer and SEM/EDX data are examined to identify the oxidation transition border of the tested material. A temperature jump is observed in all active oxidation regimes. The experimental results are found to be in good agreement with correlations from the literature.