Optimal Control of Hybrid Rocket for Sub-Orbital Ascent Trajectory

Hybrid rocket engines possess several safety and operational characteristics which provide interesting advantages over solid and liquid rocket engines for certain applications, such as space tourism. In a hybrid rocket engine, the mass flow rate of the oxidizer can be throttled to enhance the performance of the rocket. In the present work, numerical analysis of the internal ballistics and the ascent trajectory has been carried out to obtain the optimal mass flow rate of the oxidizer to maximize the altitude for a given amount of propellant and a fixed burn time. We used a genetic algorithm designed for optimal control problems. The optimal solution for the mass flow rate of the oxidizer that was obtained is kept at maximum until about one third of the burn time and then decreased gradually. The altitude reached for this case is compared with the maximum altitude reached for constant mass flow rate of the oxidizer. The results show that for the optimal mass flow rate of the oxidizer, the altitude reached is 17.6 km higher than the altitude of 106 km that is reached in the case of constant oxidizer mass flow rate.