Multi-disciplinary Optimization of Throttleable Hybrid Rocket-Based Launch Vehicle for Lunar Ascent to Lunar Gateway

This study aims to determine the optimal design and ascent trajectory for a hybrid rocketbased launch vehicle in the context of a lunar ascent mission, with the objective of reaching the Lunar Orbital Platform-Gateway which, according to NASA, is intended to be located in a Near-Rectilinear HALO orbit of the L2 southern family. A multi-disciplinary optimization problem is formulated, integrating flight and launch vehicle design variables to achieve the best mission scenario. A zero-dimensional internal ballistics model is employed to estimate key parameters such as thrust, mass flow rate, and gross mass of the hybrid rocket, while a three-degree of freedom dynamical model is used to simulate the ascent trajectory. The resulting integrated optimization problem is solved using an in house heuristic algorithm that combines particle swarm and genetic algorithms. Liquid oxygen/paraffin-wax is chosen as propellant combination for the proposed mission. A single-stage configuration is selected following a brief preliminary mission analysis based on Tsiolkovsky’s rocket equation. The possibility of throttling the engine by modulating the oxidizer mass flow rate with increasingly complex control laws is also evaluated. In particular, constant, linear, and cubic control laws for the oxidizer mass flow rate are considered. The optimal configurations obtained for the different control laws are then analyzed and compared. Lastly, to provide validity to the solutions obtained, their performance is compared with that of conventional propulsion systems optimized for the same proposed mission.