Safe, environmentally compatible and efficient air transport that is accessible to all is essential for social wellbeing and economic development in Germany and across Europe. The European Union is pursuing the goal of a zero-emission aviation system by 2050 and calls for complete commitment in research and development in aviation. To that end, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is presenting a new aviation strategy that charts the course for research towards zero-emission aviation. The ultimate aim is highly efficient eco-friendly aircraft that operate with climate-friendly propulsion concepts and sustainable aviation fuels, in line with their range and size. With its comprehensive research expertise, the DLR is positioning itself as a virtual manufacturer (Virtual OEM) primed for accelerating the energy transition in aviation. New technologies are set to increasingly lower emissions in aviation and decouple them from the expected growth in air traffic.
"DLR's ultimate vision is zero-emission aviation. Getting there will require a disruptive approach and brand new technology: our new aviation strategy sees the aircraft and air transport as an overall system. Achieving climate-neutral flight entails a considerable need for research and development," says Anke Kaysser-Pyzalla, Chair of the DLR Executive Board. "DLR is continuing to develop its systems expertise in aviation research. We see ourselves as a kind of architect. From fundamental research through to application, we work in close coordination and collaboration with the aviation sector."
"The energy requirements of future aircraft need to be reduced by at least half by 2050. This requires technology capable of reducing aerodynamic drag and total weight, together with innovative flight control and sensor systems," says Markus Fischer, Divisional Board Member for Aeronautics. "In addition to new aircraft configurations, we also require a smart mix of alternative propulsion concepts. In future, small and regional aircraft will be able to take off using battery or hybrid-electric systems, short- to medium-haul aircraft will be powered with hydrogen, and sustainable fuels will be used in conjunction with highly efficient turbines on long-haul flights. Climate-optimised flight routes offer an important savings potential for all aircraft."
DLR's new aviation strategy sets out the development challenges that need to be overcome on the path towards climate-neutral flight. It is clear that a single innovation cannot cover all areas of aviation, especially when it comes to alternative propulsion systems. Different combinations of propulsion technology and energy carriers offer promising solutions, according to the range and the size of the aircraft. This means that a broad spectrum of research efforts is necessary for new low-emission aircraft propulsion systems that together cover all types of routes:
Turbo engines with sustainable fuels for all journeys, including long-haul
Highly efficient turbofan engines and fuels produced using renewable resources offer the promise of largely climate-neutral operation on short- to long-haul flights. The entire existing fleet can benefit with minimal technical modifications to engines and infrastructure. Sustainable Aviation Fuels (SAF) lower the carbon footprint considerably and reduce the climate impact of contrails. Comprehensive test flights, safety demonstrations and extensive sustainable production capacities are necessary for the future use of SAFs.
Propulsion systems with direct hydrogen combustion for up to medium-haul routes
Using hydrogen can bring local aviation-related carbon dioxide emissions down to zero. Volume, weight, integration and safety all pose particular challenges for hydrogen-powered propulsion systems. In the medium term, hydrogen will be particularly suitable for aircraft flying regionally and on short-haul routes. Research into safe and reliable hydrogen combustion and the handling of the energy carrier should lead to commercial application in aircraft in the next five years.
Hybrid-electric propulsion systems with fuel cells for regional transport
Despite their very high efficiencies, batteries and fuel cells will only be suitable for use in small and regional aircraft for the foreseeable future. High-performance electric motors, batteries and hydrogen-powered fuel cells all need to be researched for this segment. A medium-term application for commercial aircraft may then be decided upon in the next five years.
Other key areas of research: Energy-efficient aircraft, air transport system, digitalisation
Technological developments in aviation form part of a complex overall aircraft design system that encompasses production, operation on the ground and in the air, and maintenance. As such, expertise in the aviation system as a whole is absolutely vital. Thanks to its overall systems capability in aviation research, the DLR has the expertise to act as an architect and integrator in this field.
Energy-efficient aircraft: The goal of the energy-efficient aircraft is to reduce energy consumption by up to 50 percent by 2050. Based on current research findings, reducing the aerodynamic zero-lift drag coefficient by 40 percent and the total weight by 10 percent while increasing the wing aspect ratio up to 15 will achieve this objective. Linking all the different technologies together in aircraft design poses a particular challenge.
Energy requirements of future aircraft need to be reduced by at least half by 2050. Lower aircraft energy requirements directly reduce the fuel consumption of their propulsion systems, decreasing residual emissions and offsetting the higher costs of future energy carriers. Accomplishing this requires technologies capable of reducing aerodynamic drag and total weight, together with innovative flight control and sensor systems. To ensure the optimal integration of such technologies, they must be taken into account in new aircraft configurations from the very start of the design phase.
Reduced-emissions air transport system: Climate-optimised flight paths help to reduce aviation's contribution to global warming (CO2- and non-CO2 effects). A powerful, reduced emissions air transport system would involve innovative aircraft configurations and has the potential to reduce the climate impact by using climate-optimised routing to minimise the non-CO2 effects by over 30 percent. These account for roughly two-thirds of the climate impact of aviation. Optimised long- and medium-haul flights will be particularly effective at reducing the climate impact of contrails. This is the area of greatest potential for rapidly reducing the climate impact of aviation. Besides a conducive political framework and the roll-out of technical innovations, this will require greater automation and standardisation on aircraft, in air traffic management and in flight routing.
Digitalisation: Virtualising development and approval can double the speed of innovation and allow new technologies to be brought to market more quickly. The ongoing digitalisation of design, production and operation facilitates a significant reduction in development costs and risks, along with the optimisation of the entire air transport system in terms of climate impact and economic efficiency. As a virtual manufacturer (virtual OEM), DLR is able to design future products and make them available.
DLR aeronautics research: comprehensive expertise
DLR is one of just a handful of research institutions worldwide that can simultaneously fit out aircraft for new types of propulsion system, record their emissions and model the resulting climate effects. With its 55 institutes, DLR has all the necessary expertise to drive digital development processes as part of its research programme, alongside many external partners. In particular, interdisciplinary cooperation at DLR between the areas of aeronautics, space, energy and transport is unique in Europe and essential in shaping zero-emission aviation for the future.
DLR is the only research institution in Europe that can handle the coordinated development, production and experimental testing of sustainable aviation fuels and the combustion chamber. On top of that, it can investigate findings in propulsion technology, control systems and electrical engineering under real conditions, all the way up to and including flight testing. DLR has all of the necessary research and development expertise required to address energy-efficient aviation technology. It can apply its extensive research expertise using industrial-scale manufacturing facilities, test stands, wind tunnels, research aircraft and verified digital models, all under one roof. To top that all off, it has infrastructure and expertise in developing climate-friendly air traffic management. Overall, DLR has the capability and the tools to develop system architectures in aviation up to an industrial level of technological maturity.
Last year, in the run-up to publishing its new aviation strategy, DLR published the white paper ZERO EMISSION AVIATION in conjunction with the German Aerospace Industries Association (BDLI). The new aviation strategy now sets out the technical possibilities and specifies the efforts that need to be made in research and development in order to achieve them.