Low-Altitude Plume Chemistry Signature Modeling

The inability of current plume signature codes to accurately predict the altitude in the afterburning region at which the peak signature occurs and the rate of signature decay with altitude ("afterburning shutdown") is the subject of this solicitation. A more accurate description of afterburning plume chemistry is needed, particularly for hydrocsrbon-fueled systems. The issue is that either the chemical kinetic mechanism is not known or the important reaction rate constants have not been measured in the laboratory. Accordingly, the use of computational chemistry codes which can calculate reaction rate constants from first principles is required. In order to implement the first principles quantum mechanical approach the 3D molecular structure of the species, as well as the transition state structures of the reactions must be obtained. These must be input to a quantum chemistry package for calculating potential energy surface information. Current computational chemistry codes that will be investigated include POLYRATE and TheRate. This work will demonstrate the use of these codes to calculate reaction rate constants as a function of temperature for a reaction of importance to plume afterburning chemistry.