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High Altitude Chemical Injections: Non-Thermal Chemical Dynamics and Flow Field Modeling

机译：高海拔化学注入：非热化学动力学和流场模拟

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Near UV OH(A->X) and NH(A->X) emission bands at (caret)3100 and 3360 A, respectively, have been observed in Space Shuttle engine exhaust using the GLO imager spectrograph located in the payload bay. Spectra were collected at a resolution of 4 A for daytime solar illumination conditions during low-Earth orbit (LEO) maneuvers. While it is now understood that the OH(A-X) emissions stem from solar-induced fluorescence and photodissociation of OH and H2O in the exhaust (only day phenomenon), respectively, and exhaust H2O collisions with atmospheric atomic oxygen (night and day), the NH(A-X) emissions have been determined to have a chemical reaction origin, whereby the reactants are not well established. The NH(A-X) band is of particular interest since it radiates in a spectral region where it can be readily observed from the Maui Space Surveillance Site (MSSS). In this analysis, we obtain additional clues with respect to the radiance mechanism by analyzing the temporal variation of the near-UV spectral bands. We discuss here spectral and temporal modeling of GLO measurements of a sequence of near-UV spectra (2 s temporal resolution) recorded during an extended daytime firing of a Shuttle vernier reaction control system (VRCS) engine. In the VRCS engine burn, the spectrum is dominated by the narrow NH(A-x) band. The weaker OH(A-X) band appears to be primarily produced by the reaction of atmospheric O with exhaust H2O. This is in contrast to our analysis presented at last year's AMOS conference in which the OH emission for a higher-altitude PRCS daytime burn was dominated by solar excitation channels. As discussed here, the relative importance of the solar and reactive pathways is very sensitive to both engine thrust and altitude/atmospheric O density. We also present SOCRATES flow field and chemistry calculations of the NH(A-X) and OH(A-X) emissions.

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