Investigation of Interaction of Rocket Plume with Dusty Lunar Surface

When a landing module approaches a lunar surface, the plume from its rocket exhaust interacts with dust particles on the lunar surface and entrains them. These dust particles are irregular in shape and size, and also abrasive. Dust impingement on the lunar module and its thermal optical surfaces leads to several serious problems. In the present work, a 2D axisymmetric Direct Simulation Monte Carlo (DSMC) code is developed for modeling the exhaust from the rocket nozzle. The DSMC code itself is a coupled code that models the interaction of gas molecules with entrained dust particles and vice versa. For better speed, a DSMC code with only gas expansion is simulated and its results are used to track the motion of dust particles. This step essentially decouples the effect of dust particles on the gas and speeds the simulation. The present work compares the coupled gas-dust DSMC code with the decoupled one with respect to computational time and accuracy of simulation results. The decoupled code is observed to run 10 times faster than the coupled code. Additionally, a 3D DSMC code is developed to incorporate multiple nozzles. The results of a double nozzle expansion using the 3D code and 2D axisymmetric code (that does not consider 3D effects, but is faster) will also be compared.