The simulation of ultraviolet radiation under conditions of re-entry of space vehicle from near-earth orbit

Numerical simulation is performed of nonequilibrium radiation spectrum in near ultraviolet in the range of $230$—$280$ nm from the high-temperature shock layer on the frontal surface of a sphere with a radius of $2.2$ m moving in the Earth atmosphere at hypersonic velocity of the order of orbital velocity. Radiation is considered in seven systems of bands originating from electron transitions in diatomic molecules, which may give an appreciable contribution in the given spectral range. The flow field is determined using the numerical solution of two-dimensional Navier–Stokes equations for a nonequilibrium mixture of chemically reacting gases, which are complemented with conservation equations for electronic states of molecules. The calculations are performed for the conditions of trajectory of re-entry of the Soyuz-TMA space vehicle (SV) into the Earth atmosphere in the altitude range from $70$ to $90$ km. Adequate agreement is observed with full-scale experiment involving the observation of radiation during the descent of Soyuz-TMA SV from aboard the international space station.