Contribution of Vacuum-Ultraviolet Transitions of Molecular Nitrogen to Radiative Heat Flux During Aatmospheric Reentry

Abstract

Within this work we investigate the radiative properties of molecular nitrogen with respect to the highly excited electronic states giving rise to radiative transitions occurring in the spectral range of Vacuum-Ultraviolet (VUV) radiation. This is done in order to shed light on the role of VUV radiation of molecular nitrogen in the radiative heat load encountered by a vessel during highspeed atmospheric reentry. The considered transitions bands are the Lyman – Birge – Hopfield, Birge – Hopfield I, Birge – Hopfield II, Caroll – Yoshino, Worley – Jenkins, Worley, and e'1Sigmau+ - X1Sigmag+ band. The approach to retrieve the relevant parameters for the line by line radiation simulation follows common methods of calculation, which are the reconstruction of the potential energy function via the Rydberg-Klein-Rees (RKR) method and subsequently solving the corresponding radial Schrödinger equation. Absorption and emission spectra are then calculated for a known equilibrium test condition of air plasma to illustrate the contribution of the VUV transitions to the radiation. The influence of the VUV radiation on the heat load experienced by a reentry vehicle is illustrated with an exemplary CFD calculation.