Multispectral shock-layer radiance from a hypersonic slender body

A methodology is presented for the calculation of the infrared (IR) shock-layer radiance from a slender hypersonic vehicle. An overlay technique that has been successfully employed for chemically reacting hypersonic compressed and expanding flows has been extended to model accurately the vibrational state distributions of NO, CO, water, and CO₂, which are potential shock-layer radiators in the midwave IR. The spectral predictions show that radiation from shock heated ambient CO₂ will be an important contribution at most altitudes and speeds slower than 3.5 km/s. A detailed vibrational state-specific model of CO₂ excitation has been incorporated with the flow modeling using an overlay technique. Comparisons of the spatial distributions of CO₂ vibrational states with a corresponding Boltzmann distribution at the translational temperature show that there are substantial differences in the populations. These predictions are important for the design of an upcoming sounding rocket experiment.