Quantitative Emission Spectroscopy for Superorbital Reentry in Expansion Tube X2

摘要

Asuperorbital reentry flow was realized in the X2 expansion tunnel of the Centre for Hypersonics of the University of Queensland, resulting in measurements of electronic excitation temperature, electron density, and particle densities of neutral and ionized atomic nitrogen and oxygen. A rectangular cold wall model was exposed to a flow corresponding to a 12.2 km/s flight equivalent velocity. Vacuum ultraviolet optical emission spectroscopy in the wavelength range between 116 and 185 nm was conducted through a window at the stagnation point. Spatially resolved optical emission spectroscopy of the stagnation streamline in the near-infrared wavelength range from 695 to 880 nm was conducted, analyzing the flow from the side. Population densities of excited atomic states, electronic excitation temperatures, and electron and ion densities were determined by analyzing the radiative transport in the flowfield. Additionally, the flowfield was numerically simulated using the code URANUS. Agreement in electron density (+/- 6%) and electron temperature (+/- 8%) in the equilibrium region is observed between the numerical simulations and the measurement. Significant differences between measurement and simulation in the distribution of the electron temperature at the shock are attributed to the modeling of the URANUS electron temperature.