A Systems Engineering Approach for the Transition to Zero Emission Aviation

As the world strives to eliminate anthropogenic greenhouse gas emissions to curtail climate change, among the hardest sectors to "de-carbonize" will be long-range civil aviation. If the civil aviation industry is to continue to thrive, greenhouse gas (GHG) emission-free aircraft must be designed and built. Considerable effort has been devoted to biologically-derived Sustainable Aviation Fuels (SAF), battery-electric propulsion, and H2/O2 fuel cell electric propulsion. The environmental impacts and residual carbon emissions associated with biofuels, and the energy density requirements implied by the Breguet Range Equation require a serious examination of Brayton Cycle gas turbofan engine powered flight using the combustion of a fuel with zero GHG emissions. This requires a new look at aircraft, propulsion and ground support concepts fueled by "green" cryogenic liquid hydrogen (LH2). We review the development of a new Systems Engineering approach for the transition of the medium range jet airliner market to zero GHG and minimum NOx emissions during civil airline operations. This approach incorporates Quality Function Deployment (QFD) to identify the key enabling technologies and the environmental, economic and safety figures of merit by which such technologies will be judged. The important aircraft configurations, fuel systems, combustor and propulsion design trade-offs are identified along with the risk reduction tasks to achieve a successful transition to zero emission flight by the 2050 timeframe. This paper outlines the development of the transformational technology roadmaps required to guide this transition.