Trade-Space Assessment of Liquid Hydrogen Propulsion Systems for Electrified Aircraft

In this paper, we assess the feasibility of turbo-, hybrid-, and fully electric civil aircraft propulsion systems. A modular optimization framework was developed to quantify system performance for a single-aisle transport aircraft with a mission similar to a Boeing 737-800. Various propulsion systems leveraging superconducting motors, boundary-layer ingestion, distributed electric propulsion, proton exchange membrane fuel cells, and liquid hydrogen fuel were examined for the same notional aircraft. Conventional aviation turbine fuel and liquid hydrogen were compared using the payload-fuel energy intensity, the fuel energy required per product of range and payload. For the chosen mission, the energy intensity of the hydrogen-fueled fully electric configuration was similar to that of the conventionally fueled twin turbofan baseline but produced zero carbon dioxide or nitrogen oxide emissions during flight. Relative to this baseline, a hydrogen-fueled turbofan system had the lowest energy intensity. Energy intensity increased when adding fuel cells to a turboelectric system or batteries to a fully electric, fuel-cell-powered system.