DLR, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) predicts practical ways to achieve dreams of carbon neutral flight. EXACT (Exploration of Electric Aircraft Concepts and Technologies Projects is not an exact depiction of aircraft on the drawing board, but a conceptual program for creating the craft and infrastructure of future flight.
The EXACT project is developing a concept for climate-friendly flying in commercial aviation and takes into account the complete life cycle of an aircraft, its components and its fuel. DLR looks beyond the aircraft designs themselves to include sustainable energy sources, powerplant types, and even flight route planning.
Goals and Approaches
The plan cites the following goals and approaches:
- “New DLR aviation strategy charts the research path towards emission-free flying.
- “The energy requirements of upcoming aircraft must be reduced to at least half by 2050.
- “The climate-neutral aviation of the future requires highly efficient aircraft configurations and an intelligent mix of alternative drive concepts.
- “Climate-optimized flight routes offer an important savings perspective for all aircraft.
- “By virtualizing development and approval, the speed of innovation can be accelerated by a factor of two and new technologies can be made available more quickly to the market.
- “Focus: Aviation, climate-friendly flying”
Lessons learned from any one aspect of the investigations could be applied to different forms of transportation and infrastructure.
Aircraft Configuration Options
DLR forecasts at least three concepts that use electricity and sustainable aviation fuels to clear the air and make flying possibly less expensive. One can see the base concepts in a dense PowerPoint from the Hamburg contingent of DLR.
Three options come through as being realizable and most hopeful, on time and on budget. The first is a simple adaptation of existing technology, but with a perhaps significant change in infrastructure.
Turbo drives with sustainable fuels for long distances
EXACT’s turboprop option would retain operational characteristics, but use SAF fuel option
Turboprops are already a constant in regional aviation. They are slower than pure jets and cruise at lower altitudes. Because they are slower, they use significantly less fuel. DLR notes, “This option is not only ecologically advantageous, but is also worthwhile for airlines from an economic point of view. Running on fossil fuels already reduces the impact on the climate by more than 40 percent; using sustainable fuels would reduce the impact on the climate even further. The aircraft under consideration has a range of 2,800 kilometers” (1,736 miles).
Wassertstoff (Hydrogen) Mild Hybrid
DLR EXACT mild hybrid with wassertstoff (hydrogen) used in direct combustion. The Perlan Project’s Blue Condor experiments are already using such an approach in a jet motorglider.
DLR suggests, “Hydrogen-powered aircraft can reduce climate impacts by at least 80 percent. ” DLR explains that economies require reasonable fuel production costs. That combined with synthetic kerosene could help achieve ranges up to 1500 kilometers (930 miles).
Plug-in Hybrid
DLR EXACT Plug-in Hybrid
Daniel Silberhorn, head of the EXACT project, shares a startling element of the project. “What may seem surprising at first glance is the fact that the battery-electric hybrid concept performed best. Due to the high mass of the batteries and the rather short range, operation with batteries was previously considered more promising for smaller aircraft used on short-haul flights. In fact, the plug-in hybrid architecture means that larger, market-relevant aircraft can also be powered with it.” To make this an ecological reality, “Sustainable production with a very high recycling rate and a long battery life,” are key. Batteries alone could enable 500 kilometers, while a hybrid-electric craft with sustainable fuel could travel up to 2,800 kilometers.
Added Thoughts
All three of these designs (DLR seems to have over a dozen potential candidates for future development) have longer than usual, high-aspect wings – hence the folding wingtips. These will help the craft to fit in conventional jetways. The longer wings allow added range and probably rates of climb and fuel-efficient cruising. Beyond the aircraft configurations, future airline flight will require different fuel production and distribution. clean ground support, and myriad other changes – all of which will reduce emissions from an increasingly important part of the world’s transportation network.