The German government's aviation strategy and the European "Flightpath 2050" agenda specify that CO2 emissions and, in particular, the climate impact of air traffic must be significantly reduced. To achieve the associated goals, it must be possible to fly as CO2-neutrally as possible and ideally also climate-neutrally. However, this not only requires the design and development of extremely efficient aircraft configurations and engines. In addition, CO2-neutral fuels generated with renewable energy, so-called "Sustainable Aviation Fuels" (SAF), must be used and the remaining climate impact must be reduced due to the continued presence of engine emissions in the atmosphere. In addition to these fuels, which are available in the medium term, the use of hydrogen as a long-term energy carrier must also be investigated and evaluated.
Current aircraft designs require certain flight speeds and associated optimum flight altitudes for efficiency and also cost reasons. In the future, not only efficiency, but in particular the sum of all climate effects, i.e. the influence on the temperature of the atmosphere, must be considered as a target variable. This will have an influence on the optimum speeds, flight altitudes, flight routes and thus also on the design of the aircraft and the engine.
The DLR project KuuL (Klimafreundlicher ultra-effizienter Langstreckenflug) is dedicated to this task. In this project, scientists from six DLR institutes are investigating and designing the influence of new, synthetic fuels and alternative mission profiles (different cruise altitudes and cruise speeds) with aircraft and engine designs adapted to these. In addition, aircraft and engines using hydrogen as an energy carrier are also considered. Criteria will be the impact on the atmosphere as well as economy and flight time. Building on previous projects considering conventional fuels this project shall focus on tailored synthetic fuels and improved atmospheric models for assessing the impact on the climate and to determine the requirements for the most promising aircraft and engine operation conditions. By designing new aircraft and engines snowballing effects will be exploited as far as possible.
The contribution of the Institute of Aerodynamics and Flow technology consists of the project lead and the flight physical design of aircraft using SAF as energy carrier. For this purpose, aircraft will be designed and optimized for different flight altitudes and speeds. These will then be analyzed by the project team with respect to their effect on the climate and their operating costs.