Influence of Chemical Kinetics on Ultraviolet Radiation Behind Hypersonic Bow Shock

Simulations of UV radiation behind a hypersonic bow shock are presented. Results are compared with data from the bow shock ultraviolet flight experiment, which flew a 10.16 cm radius sphere-cone vehicle at [Formula: see text]. Altitudes between 20 and 70 km are studied. Flow simulations are performed with the LeMANS computational fluid dynamics code using the Park and Modified Marrone–Treanor (MMT) chemical kinetics models. Radiation is modeled using NASA’s NEQAIR code. Simulations show reasonable agreement with experimental data. Between 30 and 60 km, NO is the dominant source of UV radiation. Outside this range, [Formula: see text] Schumann–Runge emission is significant. Below 45 km, NO excited states are populated by collisional excitation and closely follow a Boltzmann distribution. At higher altitudes, exchange reactions dominate and produce significant overpopulation of excited states. Differences between Park and MMT results are attributed to the [Formula: see text] dissociation rate. Below 45 km, the higher [Formula: see text] dissociation rate of Park produces lower temperatures and less UV radiance than MMT. Above 45 km, the Park model predicts higher NO formation and more UV radiance. The dependence of radiance on altitude for the MMT model is in good agreement with experimental data, whereas the Park model has inconsistent agreement at different altitudes.