<p>The purpose of this study is to investigate and design a non-atmospheric combustion chamber equipped with secondary holes and dilution. Initially, in order to validate the results, both zero-dimensional and numerical simulations of a land-based gas turbine combustion chamber were employed. Subsequently, the zero-dimensional design of the non-atmospheric combustion chamber was carried out, and using thermodynamic design methods namely, the pressure drop based approach and the mass flow distribution method the shell diameter of the chamber was calculated. The flame tube was extracted from a land-based gas turbine chamber, and in the three-dimensional design of the non-atmospheric combustion chamber, only the chamber shell, the upstream diffuser, and the downstream nozzle were designed. Ultimately, the designed non-atmospheric combustion chamber was simulated using ANSYS Fluent software. For turbulence modeling, the RNG k-ε model was applied, while non-premixed combustion modeling was used to simulate the combustion process. Furthermore, in order to identify vortices within the non-atmospheric combustion chamber, the 2λ criterion was utilized. The results indicate that in the non-atmospheric combustion chamber, vortices and the flame are concentrated in the initial (dome) region of the chamber, demonstrating the presence of a stable flame. The pressure drop within the non-atmospheric chamber under combustion conditions was found to be 3.8%. The discrepancy between the zero-dimensional and three-dimensional simulation results was less than 0.05%, while the difference between the zero-dimensional simulation results and the reference manual data was less than 8% across all shaft speeds. Additionally, the fuel mass fraction distribution along the chamber shows that the fuel is fully consumed by the end of the chamber.</p>