A solar furnace coupled to a microwave induced plasma for the simulation of the space vehicles entry (atomic recombination)

Abstract
During the atmospheric entry phase, the surface temperature of the protective heat shield of hypersonic vehicles increases with the atom recombination from the dissociated gas plasma. The excess of heating coming from the oxygen and/or nitrogen recombinations (Earth entry) or carbon monoxide and/or oxygen (Mars entry) on the surface of the material depends on the entry environment (pressure, temperature, gas flow velocity) and on the protective coating material catalycity. A ground simulation has been realized to evaluate the catalycity of such materials using direct atom loss (chemical approach) and heat transfer (thermal approach) measurements. The set-up associates a solar radiation concentrator (for high temperature) and a microwave generator (for gas dissociation) to partially reproduce the atmospheric entry conditions. The catalytic activity of several ceramic materials (carbides, nitrides, oxides) under different pressure and temperature conditions is measured, using the two previous approaches. Finally, the experimental results obtained with both the approaches lead to the determination of a catalycity scale and the evaluation of the physico-chemical behaviour of ceramics under atmospheric entry conditions.