Generative design of hybrid-electric aircraft propulsion systems using evolutionary algorithms

Abstract

The electrification of aircraft propulsion offers significant potential for emission reduction. Hydrogen-powered hybrid-electric systems combine zero carbon emissions with high energy density, enabling greater range than purely battery-electric concepts. Their tightly coupled subsystems, however, require an integrated, system-level design approach. This study presents the architectural optimisation of a hydrogen-electric multi-string propulsion system for ultralight aircraft. Power is distributed across several parallel fuel cell strings, allowing lighter air-cooling configurations. A model-based systems engineering (MBSE) framework is coupled with a genetic multi-objective optimisation algorithm to determine key sizing parameters, including the number and power of the fuel cells, as well as the energy management strategy between fuel cells and the battery. The methodology is applied to the Breezer UL B400-6 ultralight aircraft and demonstrates clear trade-offs between system mass and flight duration, offering valuable insights for early-stage design of multi-string hydrogen-electric propulsion architectures.