Effects of catalytic recombination on the surface of metals and quartz for the conditions of entry into the martian atmosphere

Heat transfer to water-cooled surfaces of metals and quartz is studied experimentally in subsonic jets of dissociated carbon dioxide at a stagnation pressure of 80 hPa and enthalpy of $9$ and $14$ MJ/kg, corresponding to the descent conditions of the ExoMars space vehicle into the Martian atmosphere, using an RF induction plasmatron at the Institute for Problems in Mechanics, Russian Academy of Sciences. The measurements of heat fluxes to surfaces of different materials showed the significant effect of the catalytic properties of surfaces that can be arranged in the following descending order of the heat flux: silver, copper, stainless steel, quartz. The effect of strong modification of the silver surface is recorded during the tests; the maximum value of the heat flux is achieved after $15$-min exposure of the surface to the jet. In the computational analysis of heat transfer, we used a two parameter model of heterogeneous recombination of $\mathrm O$ atoms and $\mathrm{CO}$ molecules at the surface. With this model, the effective recombination coefficient of $\mathrm{CO}$ molecules is determined on the water-cooled surfaces of quartz and stainless steel, based on the experimental data on heat fluxes.