The unstructured two-dimensional grid-based computation of selective thermal radiation in $\mathrm{CO}_2$–$\mathrm{N}_2$ mixture flows

The possibility of applying the $P_1$ approximation of the spherical harmonics method to the computation of the radiant heat transfer in heterogeneous volumes of complicated geometry is investigated. This approximation is used to evaluate the radiant heating of the surface of a spacecraft descending in the Martian atmosphere. The chemical composition of the gas heated behind the shock wave is calculated by using a kinetic model including 79 chemical reactions and ten components, such as $\mathrm{CO}_2$, $\mathrm{CO}$, $\mathrm{C}$, $\mathrm{O}$, $\mathrm{O}_2$, $\mathrm{C}_2$, $\mathrm{N}$, $\mathrm{N}_2$, $\mathrm{CN}$, and $\mathrm{NO}$. The optical properties are set by a spectral multigroup model computed with the help of the ASTEROID computer code with averaging over the rotational molecular spectrum structure in each group. The mechanisms of the radiant heating of the surface of descent space vehicles in the Martian atmosphere are studied.