Experimental and numerical study on radiating shock tube flows for spacecraft reentry flights

The objective of this study is to investigate thermochemical processes in the shock layer by shock-tube experiments. In this study, the temporal profile of radiation intensity is observed by time-resolved emission spectroscopy. The measured radiation profiles are compared with the calculated radiation profiles to validate the chemical reaction processes considered in the calculation. The measured radiation profiles are different from the calculated ones, especially in the region ahead of the shock front. The measured radiation intensities for N-2, N-2(+), and N start to increase ahead of the shock front. On the other hand, the calculated radiation intensities start to increase at the shock front. This difference could be caused by precursor phenomena which are not considered in the present calculation. The details of precursor phenomena has not been clarified. However, the present study has indicated some of the interesting results. From the radiation profiles observed in the region ahead of shock front, electronic excitation of N-2, photoionization and photodissociation of N-2 are found to occur. It is also found that the radiation profiles between experiment and calculation differ in the shock layer, showing that precursor phenomena have a great influence on thermochemical processes in the shock layer. In future, thermochemical processes should be modeled by incorporating precursor phenomena.