A nozzle is a device that is designed to regulate the direction and characteristics of the combustion gas products of jet engines. So, the nozzle performance has a significant impact on the mission achievement. This paper is concerned with the internal ballistics of the nozzle aiming to estimate pressure and thermal loads on its walls. Computational fluid dynamics is applied to analyse the effect of changing nozzle internal profile on the resulting thrust, flow energy losses, and nozzle wall structure. Area ratios at the inlet, critical, and exit sections are considered as constraints for the examined design. Two different sets with 4 different profiles for each are investigated. The results show thrust, entropy losses across the nozzle and the static pressure and temperature at nozzle wall. Bell shape profiles produce better performance compared to other profiles. Changing the internal profile of the nozzle causes significant change in pressure and temperature loads acting on nozzle wall structure.