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Abstract. An important problem for space vehicles is contamination of the spacecraft surface by combustion products and unburned fuel exhausting from control thruster nozzles. The objective of the present work is a detailed simulation of the backflow in the case of gas exhaustion from the nozzle into vacuum. A specific feature of this problem is the drastic expansion of the initially dense flow at the nozzle exit, which makes necessary simulations of the near-continuum flow inside the nozzle, the transitional flow near the nozzle exit, and the free-molecular flow outside the nozzle. The simulations are performed by a combined Navier-Stokes/DSMC approach.

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In order to evaluate the behavior of the intermediate experimental vehicle (IXV) in the upper layer of the atmosphere, series of computations were carried out by means of the Direct Simulation Monte Carlo (DSMC) method, which are reported hereby. First an introduction is given about the IXV mission followed by a short explanation on DSMC and the computational methodology. A ¦rst validation case is demonstrated for computations based on the geometry of the Apollo capsule, showing good agreement with a reference in literature. Then, simulations of the IXV are presented, including §owthruster interaction. Finally, the result matrix of aerodynamic properties is shown.

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