Design Optimization of a Mg/CO2 Hybrid Rocket Engine for Mars Ascent Vehicles

This paper focuses on the design optimization of the hybrid rocket engines of a two-stage Mars ascent vehicle. In situ resource utilization is considered for the propellants, which are a mixture of nitrous oxide and carbon dioxide as oxidizers, and paraffin-based wax loaded with Magnesium as solid fuel. Two in situ resource utilization strategies are investigated: a short-term mission concept involving the production in situ of carbon dioxide using a scroll compressor, and a long-term mission concept in which all the propellant is collected or produced on Mars except the paraffin-based wax, which is carried from the Earth. The optimization of the hybrid rocket engine and ascent trajectory is performed using a coupled approach. A particle swarm optimization algorithm is used to fine-tune engine design parameters, namely initial mixture ratio, initial feeding system pressure, nozzle expansion area ratio, the amount of carbon dioxide in the oxidizers mixture, the amount of Magnesium particles in the fuel grain, and the initial Mars Ascent Vehicle mass, whereas an indirect method optimizes the ascent trajectory to the target orbit. The landed mass of the Mars Ascent Vehicle is fixed and equal to 500 kg. The optimized solutions achieve significant payload gains when compared to conventional hybrid Mars Ascent Vehicles. These results highlight the feasibility of in situ resource utilization for hybrids on Mars, holding implications for the future human exploration of Mars.