Characterisation of Wake-Region Optical Emissions From an Ablative Hypersonic Glide Vehicle

The effect of ablation on the structure and chemical composition of the wake behind the HIFiRE-5 vehicle at Mach 12.6 and 30 km altitude is examined to enhance understanding of possible wake-region emission spectra. A coupled flow-radiation-ablation numerical model is developed to resolve wake-region translational and vibro-electronic temperatures and the number densities of both air and ablation-derived species. For an ablating vehicle, carbon monoxide (CO) and carbon dioxide (CO₂) are identified as the major ablation products entering the wake, while wake-region nitric oxide (NO) is also enhanced relative to the non-ablating vehicle. The developed wake exhibits two apparent neck positions, driven by forebody boundary-layer crossflow, producing localized peaks in translational and vibro-electronic temperatures in the wake.