A series of CFD simulations with gradually increasing timesteps is considered in this paper to improve efficiency in analyzing a 200-mm caliber sounding rocket nozzle. The accuracy of this method is compared to a simulation using a single timestep size for the entire burning duration. The simulations are conducted using two different calculation approaches. The first set used a constant timestep of 0.01 s throughout the burning period of 10 s, whereas in the second set, the timestep started at 10–4 s and increased tenfold up to 0.1 s. The results demonstrated consistent trends in crucial properties, including static pressure, wall total heat flux, and static temperature contour for both methods. Both simulations indicate that the highest heat flux of 3.4 MW/m2 occurs in the nozzle throat area within the first second.