Monte Carlo Direct Simulation of Axisymmetric Rarefied Gas Flows Through Thruster Nozzles for Spacecrafts

Axial symmetric flows of a mono-atomic rarefied gas exhausted through the thruster nozzle of an artificial satellite were numerically simulated by the Direct Simulation Monte Carlo method, since the transitional flow regime occurs at altitudes where the enhancement region is several orders of magnitude larger than the nozzle throat diameter of the thruster (high altitude rocket).

On macroscopic flows in the nozzle or the orifice, the effects of Knudsen numbers are revealed. At lower Knudsen number regions, the flows are more accelerated by the effects of inter-molecular collisions. On the inside surface of the nozzle, macroscopic velocity and temperature distributions are built up in the radial direction. At lower Knudsen number regions, the thickness of these boundary layers are getting thinner.