Nitric Oxide Spectroscopic Measurements of a Shock-Boundary Layer Interaction in Hypervelocity Flow

Spatially resolved emission spectra are collected in the post bow shock and reattachment shock region of hypervelocity flow over a double wedge. The Hypervelocity Expansion Tube (HET) is used to generate high Mach number, high enthalpy flow (M $=7$, $h_{0}=8$ MJ/kg) over a 30-55 degree double wedge. The NO $\gamma$ band ($A^{2}\Sigma^{+} - X^{2}\Pi$) emission is measured in the UV range of 210-250 nm. Detector exposures occur at select times throughout the flow development process to study temporal changes in thermal and chemical non-equilibrium. Profiles of vibrational band intensity and spectra as a function of distance are provided. Through a fitting procedure, the experimental spectra are matched with synthetic spectra to obtain an estimate of the excitation temperature of the NO molecule. The result is a temperature profile of the post-shock NO* with downstream distance.