<p>This study employed the direct simulation Monte Carlo (DSMC) method to model the rarefied-plume field and the discrete ordinates method (DOM) to analyze the radiative behavior of alumina particles under various conditions. A coupled computational framework integrating DSMC simulations via SPARTA, Lagrangian particle tracking (LPT) via OpenFOAM, and an in-house radiative base-heating solver was developed and applied. The exhaust plume analysis revealed substantial diffusion and backflow under vacuum conditions, which resulted in a reduction in gas temperature. Consequently, the reduced temperature justified neglecting radiative heat transfer from the gas phase. For a fixed propellant composition, variations in base heating were analyzed as a function of particle size. In addition, for a fixed particle size, the effect of propellant composition on base heating was examined. The results indicate that radiative base heating increases rapidly from the submicron to micron particle-size range, whereas the rate of increase diminishes markedly for larger particles. Base heating also increases with increasing aluminum mass fraction in the propellant. Because formal benchmark validation of the modified radiation coupling procedure has not yet been completed, the predicted radiative-heating levels should be interpreted as engineering-level comparative sensitivity indicators for particle-driven base heating, rather than as fully validated absolute local heat-flux predictions.</p>