Investigations of Surface-Catalyzed Recombination Reactions in the Mars Atmosphere

Abstract

In the design of a thermal protection system (TPS) for a planetary entry vehicle, accurate modeling of the trajectory aero-heating poses a significant challenge owing to large uncertainties in chemical processes taking place at the surface. Even for surface-catalyzed reactions, which have been investigated extensively, there is no consensus on how they should be modeled; or, in some cases, on which reactions are likely to occur. Current TPS designs for Mars missions rely on a supercatalytic boundary condition, which assumes that all dissociated species recombine to the free stream composition. While this is recognized to be the the most conservative approach and leads to an increased TPS mass, discrepancies in aero-heating measurements in ground test facilities preclude less conservative design options. The present work is aimed at providing more information about surface catalyzed reactions for Mars exploration missions. Measurements of dissociated species above a catalytic surface are obtained using two-photon absorption laser-induced fluorescence (TALIF) implemented in a new 30 kW inductively coupled plasma torch facility.