This study is aimed at the development of methods of direct simulation Monte Carlo(DSMC) computations of ionized rarefied gas flows formed around reentry space vehicles.Ionization processes should be taken into account in studying aerothermodynamics of superorbital vehicles moving with velocities greater than 10 km/s,where a significant portion of the gas in the shock layer is ionized.The main mechanism of ionization in such a flow is ionization by an electron impact,and the associative ionization reaction is one of the initiating processes.