Modeling of emissions from the Soyuz, progress, and mir rocket exhaust plumes at high altitudes

Modeling and calculations of ultraviolet radiation from the Soyuz-TM spacecraft and the Space Shuttle thruster plumes interacting with the ambient gas at low earth orbit conditions are presented. The Soyuz-TM spacecraft thruster firings was observed by the Mir station at relatively short ranges, whereas, onboard spectrographic data was taken of the shuttle thruster firings. Both sets of observations characterize the radiance from hydrazine thrusters at altitudes of about 300 km. The studies were performed with the direct simulation Monte Carlo method. The results presented here extend our earlier work in which we examined two UV emission mechanisms, the formation of OH(A) due to water dissociation by atomic O and the formation of NH(A) by the reaction of atomic O with hydrazine fragments. The previous axisymmetric calculations are extended to three dimensions to study the variation of the UV emissions with respect to aspect angle. Comparison of the angular dependence of the data and modeling provides insight into the energy dependence of the chemiluminescent reactions.