Streamwise measurements of a hypersonic shock layer radiation

Abstract A simultaneous spectroscopic and visualization system was developed to study hypersonic shock layer radiation along a streamwise line-of-sight. The system was implemented to observe emissions ahead of projectile travelling at approximately 7 km/s in a controlled argon environment at the JAXA/ISAS two-stage light gas ballistic range facility. Experimental conditions were designed to establish equilibrium flow within the shock layer, enabling comparison of the measured emission spectra with equilibrium radiation models. For this comparison, stagnation point radiation was extracted from the experimental data with the aid of the co-axial visualization system. Radiation calculations were performed using the SPRADIAN07 radiation code, with equilibrium flow properties obtained using the NASA CEA code. The dominant thermochemical structure in the shock layer was analyzed by streamlining the radiative transfer within a piecewise layer model. Parameterized layer properties were iteratively refined until the calculated spectra matched the experimental spectra. The findings demonstrate that the current measurement method provides useful diagnostic information for estimating the dissociating, partially ionizing, and ablating structure of hypersonic shock layers in addition to reducing uncertainty associated with line-of-sight measurements.