During the reentry process of a spacecraft into atmosphere

the spacecraft encounters a complex thermal environment

causing the surrounding gas to undergo reactions such as vibrational excitation

dissociation

ionization and recombination. These reactions lead to significant thermodynamic and chemical non-equilibrium effects. Although numerous studies have been conducted on the chemical non-equilibrium dynamics and various chemical reaction models have been developed

significant discrepancies in modeling results may be obtained by using different models. In this study

nitrogen

the major component in atmosphere and commonly used in ablation experiments

is selected as an example for obtaining the simplified chemical reaction model with the aid of the genetic algorithm and dynamic programming method. By presetting a maximum relative discrepancy of 10%

a set of simplified chemical reaction pathways are obtained involving 10 species including electrons

ions

atoms and molecules in ground state

and excited neutral species involved in 23 chemical reactions. Under the local chemical equilibrium state

the species number densities under different translational and vibrational non-equilibrium degrees are calculated and compared with data from the literatures. The results preliminarily validate the reliability of the chemical reaction screening method and the calculated number densities for a non-equilibrium nitrogen plasma. This study provides a theoretical guidance for future studies on the non-equilibrium transport mechanisms of air plasmas under real gas conditions and the ground ablation experiments for typical components during spacecraft hypersonic reentry processes.