Nonequilibrium Ionization and Radiation in Hydrogen-Helium Mixtures

Abstract

A theoretical model describing the nonequilibrium processes occurring behind a normal shock wave in a hydrogen-helium mixture is developed by assembling the latest information on physical properties and by comparing the calculation with the two sets of shock-tube data obtained in the 1970s. The cross-section value of 4 x 10(-17) for electronic excitation of hydrogen atoms by the impacts of hydrogen and helium atoms derived earlier by Leibowitz is confirmed. The intensity of radiation in a nonequilibrium flow is typically twice that in an equilibrium flow. A sample calculation is made for an entry flight in the atmosphere of Neptune to show that the radiative heat load under nonequilibrium is more than twice that under equilibrium.