OXIDATION AND CATALYCITY OF THERMAL PROTECTION MATERIALS AT HIGH TEMPERATURE

When a space vehicle enters in planetary atmospheres like Earth (air) and/or Mars (CO2), oxidation and catalycity coupled phenomena occur on the thermal protective materials of the nose cap and wing leading edges conducting to an important excess of heating and possible damage of the materials. At the PROMES-CNRS laboratory (formerly IMP-CNRS), in the research field "Interaction high solar fluxes-matter", oxidation under plasma conditions, and particularly the active-passive transition in the oxidation of silicon-based ceramics and the catalytic recombination of atomic oxygen under the same conditions are studied. The most important conditions for the ground simulation (high temperature, non-equilibrium plasma flow) have been realized in the MESOX set-up which associates a solar radiation concentrator and a microwave generator. In this paper, are presented some results about the transition between the active and passive oxidation regimes and the recombination of atomic oxygen and/or carbon monoxide at the surface of sintered silicon carbide at high temperatures and in a total pressure range of 102-104 Pa. The comparison is made between the two atmospheres: air (Earth entry) and CO2 (Mars entry) for the oxidation transition domain and for the atoms recombination.