Vibrational relaxation times of diatomic molecules and rocket performance

Abstract

Computations are presented for the variation of vibrational excitation probabilities with temperature for mixtures of O_2 and N_2, and of HF and H_2. The values of six different excitation probabilities in each mixture are reported for temperatures up to 3000ºK. For each of the probabilities there is a lower temperature limit given, below which the theory of Schwartz, Slawsky, and Herzfeld, which is used here, is not applicable. Using the results for H_2-HF mixtures, we present some considerations which suggest that the expansion through the de Laval nozzle for representative H_2-F_2 rocket motors may be taken as vibrational near-equilibrium flow.