The internal flow choking and other design challenges associated with development of high-performance dual-thrust motors (DTM), because of their large size, high length to diameter ratio, and demanding thrust-time trace shape requirement, were discussed. At the subsonic inflow conditions, the occurrence of internal flow choking in DTMs was due to the formation of a fluid-throat at the beginning of the port divergence location induced by area blockage caused by boundary layer displacement thickness. It has been observed that a 55% increase in the upstream port area of the DTM contributes a 25% reduction in blockage factor at the transition region. The velocity on the duct axis, the displacement thickness, and the momentum thickness parameters attain their maximum values when the potential core is eliminated. The occurrence of a chocked flow condition at the port divergence region of the DTM with a narrow upstream port is very high and lead to the formation of shock waves.