Multi-objective optimization of thrust control strategies for electric pump-fed rocket engines

Abstract

Electric pump-fed rocket engines are critical for reusable launch vehicles due to their ability to flexibly regulate thrust and reduce structural mass. This study presents a novel multi-objective optimization framework to determine optimal thrust control strategies for a liquid oxygen/methane electric pump-fed rocket engine, operating across a thrust range of 20 %–100 %. The framework addresses trade-offs among specific impulse, electric energy consumption, and thermal protection reliability. Using the Non-Dominated Sorting Genetic Algorithm (NSGA-III), we evaluated candidate strategies and identified well-distributed Pareto frontier solutions, refined through a comprehensive evaluation method combining weighting and the Technique for Order of Preference by Similarity to Ideal Solution. The optimal strategy employs monotonic pump speed control for 80 %–100 % rated power level and joint regulation of pump speed and injector opening for 20 %–70 % rated power level, with fully open main valves to minimize energy consumption. Below 60 % rated power level, strategic mixture ratio reductions mitigate heat transfer deterioration in subcritical methane, ensuring thermal reliability, while fuel injector throttling enhances cooling capacity, increasing specific impulse by up to 5 % at 40 %–60 % rated power level. These findings demonstrate the effectiveness of the Non-Dominated Sorting Genetic Algorithm for complex propulsion optimization and provide practical strategies for enhancing engine performance in reusable launch systems, advancing sustainable space exploration.