Modeling of radiation events from a side jet atmospheric interaction at high altitudes

Highly nonequilibrium radiation transitions from electronically excited states generated by collisions of atomic oxygen with reaction control system thruster plumes is modeled for different altitude and vehicle velocity conditions. The flow field results are obtained using a Navier-Stokes solver to obtain the flow inside the nozzle and the direct simulation Monte Carlo method is used to simulate the chemically reacting, three-dimensional plume-atmospheric interaction. The frequency of radiation events are compared for two types of overlay methods and with direct simulation in DSMC. The distribution function for collisional relative velocities is explored and used to interpret the sensitivity of the number of radiation events to free stream altitude, temperature, velocity, and to the radiation mechanism activation energy.