The establishment of a sustainable human presence on the Moon requires reliable and efficient surface operations. A critical challenge for lunar landers is the interaction between rocket exhaust plumes and the lunar regolith, which can mobilize high-velocity dust particles and pose risks to equipment and infrastructure. This thesis investigates the modelling of plume-surface interaction (PSI) under near-vacuum conditions, where the expanding exhaust transitions from dense, continuum flow near the nozzle to rarefied, non-equilibrium conditions farther away. Classical Navier-Stokes-based Computational Fluid Dynamics (CFD) fails in the rarefied region, while particle-based Direct Simulation Monte Carlo (DSMC) methods are computationally expensive in dense regions.