The nozzle placement, amongst other geometrical features of a solid rocket motor nozzle, has a profound effect on the performance of a solid rocket motor. There are two options for nozzle placement, namely, external and submerged. A two-phase, 3D numerical simulation was conducted to give a qualitative sense of the differences in performance parameters and internal flow features that are introduced by using either of the placement configurations. The Large Motor of NASA's IUS (Inertial Upper Stage) was chosen as the base model for conducting this study. The original motor was designed using a submerged nozzle, and in this study, that configuration is compared with an alternate one that uses an external nozzle of the same expansion ratio, throat diameter, and divergent section shape.