Reduced environmental impact by lowered cruise altitude for liquid hydrogen-fuelled aircraft

Abstract

Environmental concerns, as well as the expected depletion of fossil fuel resources, have become the driving forces for research and development towards the introduction of hydrogen energy into air traffic. The present paper is a summary of a study that was carried out within the European sponsored project CRYOPLANE, co-ordinated by Airbus Germany. The objectives of this study are to re-optimise and compare two equivalent medium-range aircraft – one kerosene-fuelled and one LH 2-fuelled – for reduced cruise altitude, from an environmental point of view. By lowering the cruise altitude, the contribution to global warming might be reduced at the expense of increased fuel consumption and pollutant emissions. In order to assess the global impact, in terms of global warming, from the emissions discharged on a certain mission, a simple parametric model is employed. The results suggest that introduction of cryoplanes will improve the environmental performance, particularly in terms of global warming. Provided that an increase in fuel consumption in the order of 10% and an increase in TOM of a few percent are accepted, the results suggest that cryoplanes should cruise at an altitude of about 2–3 km below where conventional aircraft cruise today in order to considerably reduce the environmental impact.