Online

Voll, Brandon

Mechanical Engineering

2021

M.S.

Uncertainties in surface catalytic reaction rates in a CO2 plasma have led to overdesign of thermal protection systems, which has caused planetary entry vehicles for the Martian atmosphere to be heavier than necessary. This, in turn, has decreased the available payload of various missions. A better understanding of these reaction rates will allow more precise development of thermal protection systems leading to safer and more effective atmospheric entry vehicles. Near wall measurements in a plasma facility using laser spectroscopic techniques with sub-millimeter spatial resolution provide a method to determine surface-catalyzed reaction efficiencies over metallic surfaces. The present work includes laser induced fluorescence measurements of oxygen atoms and carbon monoxide molecules in a predominantly CO2 plasma produced by inductive coupling. Measured catalytic recombination efficiency values suggest that molecular oxygen recombination is the dominant surface-catalyzed reaction, while carbon monoxide does not appear to react heavily near the surface. For a surface temperature of 1100 K, O-atom and CO recombination coefficients over copper were 0.0490 ± 0.0088 and 0.0112 ± 0.0016 respectively and CO recombination over platinum was 0.0005 ± 0.0004. This implies that a super-catalytic boundary condition, wherein all species recombine to form carbon dioxide, is overly-conservative.