Engine exhaust plume interactions with a planetary surface

Kurzfassung

When a planetary lander descends, the rocket engine exhaust plume impinges on the planetary surface and entrains solid soil particles into a �ow. These eroded particles accelerate to high velocities and form dangerously energetic dust sprays. The dust sprays decrease visibility and jeopardize the landing vehicle and hardware nearby. The understanding of the risks is important to improve the safety of the future planetary missions. This Master's Thesis contributes to this objective by introducing a three-stage simulation framework. In space the exhaust plume expands into a vacuum and becomes a rare�ed �uid. A continuum hypothesis of the Computational Fluid Dynamics (CFD) breaks down and therefore a molecular level Simulation method, The Direct Simulation Monte Carlo (DSMC), should be applied. The plume impingement in a lunar environment was modelled by a one-way coupled CFD-DSMC simulation framework. The lunar surface erosion was modelled as a stochastic process and the soil particle trajectories were computed from the interactions between the particles and the �ow �eld. The �ow �eld was obtained as an output data from the DSMC simulation. The simulation framework was successful and provided qualitatively comparable results for the plume �ow �eld and the impingement phenomena with respect to the results in the literature. The resulting soil particle trajectories indicate a dependence on the initial conditions. The range of the soil particle trajectory is suggested to correlate with the initial vertical velocity. The slope of the trajectory was proportional to the particle diameter. The applied formulations for aerodynamic forces in a rare�ed �ow were found cumbersome and constrained. In addition several minor remarks have been discussed.