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Dougherty, Maximilian

Mechanical Engineering

2011

MS

In the design of a thermal protection system 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. Modern thermal protection system designs for Mars missions are thus forced to rely on a supercatalytic boundary condition, in which it is assumed that all dissociated species recombine to the free stream composition. This is recognized to be the most conservative approach, as it yields the highest computed heat flux, and leads to an increased TPS mass at the expense of scientific payload.
Unfortunately, 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, specifically the behavior of atomic oxygen and CO and their participation in these reactions. Measurements of dissociated species above catalytic and non-catalytic surface are obtained using two-photon absorption laser-induced fluorescence (TALIF) implemented in the 30 kW Inductively Coupled Plasma Torch Facility located at the University of Vermont. The measured data includes spatially-resolved temperature and number density for O and CO in the reacting zone just above the material surface.