Examination of OH ultraviolet radiation from shock-heated air

Two recent sounding rocket experiments obtained spectral data at wavelengths of 200-400 nm from the shock-heated air surrounding a vehicle under flight conditions of 3.5 km/s at altitudes of 40-70 km and 5 km/s for altitudes of 110-65 km. Previous analyses of the data have emphasized modeling the radiation from the NO molecular system. The chemical kinetics of OH, a trace species in the flow, and the electronic state excitation mechanisms are simpler than those for NO. Hence, the comparison between modeling and data potentially provides a clearer assessment of the modeling of the flow thermochemical processes. This article discusses the OH flowfield and radiation models that we have developed, comparisons with data, and the implications of this work to ongoing NO flow and radiation modeling. Additional data from the side-viewing spectrometers from the 5-km/s flight will also be presented and analyzed. The angular dependence of the photometer data was compared with a solution obtained from a viscous three-dimensional flowfield calculation with reacting water chemistry.