Unguided sounding rockets are vehicles that carry scientific experiments and/or sensors to collect data during their trajectory and are also called sub-orbital rockets. Such rockets do not have active control and can get through the Earth's atmosphere. The parameters relating to the flight must be properly analyzed in your preliminary design. The Open Rocket flight simulation software is a widely used open-source project developed by Sampo Niskanen. However, it has some simplifications compared to its documentation which does not specify the calculations of critical parameters for the stability of the rocket during its flight path, and do not calculate data related to dynamic stability, which is associated with the corrections that the system will give to disturbances during its trajectory. Therefore, this work presents a flight simulation of a rocket with 6 degrees of freedom in Matlab/Simulink. The obtained results were compared with the Open Rocket data and show that the proposed simulation is efficient and presents reliable and accurate data. In addition, the developed algorithm allows the expansion of Open Rocket's capabilities, as well as the implementation of a control system.