For decades, visions of the future have repeatedly portrayed weird and wonderful aircraft that resemble rays, arrows, or even flying saucers. Yet today’s planes look much the same as they did at the dawn of commercial air travel. When is that going to change?
Prof. Mirko Hornung: The question we should be asking is: does it have to change at all? It makes sense to develop new airplane configurations only if they offer significant advantages over the conventional design. That’s why planes still look much the same today. So far, other configurations haven’t proved so much better that they would be worth implementing. If we’re talking about enhancement of just a few percent, we can usually achieve this through continuous improvement. It also has to be said that the industry hasn’t been idle either. While aircraft exteriors might not appear to have changed much since the Boeing 707, the interior is quite a different story. Over the past seven decades of commercial air flight, we have made substantial improvements to our aircraft. In that time we also reduced fuel consumption by almost 70 percent compared to the very first passenger jets, like the Boeing 707.
What research priorities and technological developments do you see defining the industry over the next two decades?
Hornung: All forecasts indicate that the number of aircraft is set to triple by 2050. The targets have been set—lowering CO2 emissions by 75 percent, significantly reducing nitrogen oxide emissions, and lessening noise—and give rise to a wide range of topics. Airplanes are only one piece of the puzzle; airports also play a role, as does fuel supply and the transport system as a whole. One driving force will certainly be the continued development of energy and propulsion systems. This area shows highly promising technological approaches that we are exploring in close collaboration with MTU Aero Engines. For instance, we have recently been looking into new cycles, so-called composite cycles, in which different thermodynamic cycles are combined in order to once again dramatically improve engine efficiency. There still seems to be a lot of untapped potential here. Electric-hybrid propulsion systems—that is, a combination of electric motor and internal combustion engine—are of course also a topic for us. Only a few years ago, people were saying there’s no way they can work in a larger aircraft. But the idea no longer sounds quite so absurd.
Wait a moment, are you saying that electric-hybrid propulsion systems can work in larger passenger aircraft?
Hornung: In theory, yes. But it’s something that has to be examined very closely. It’s been proved that in principle it would be possible. One of our main tasks now is to look at how we need to develop the individual components and technologies; in other words, what has to happen if electric-hybrid propulsion systems are to represent an advantage when operating aircraft. Right now we still lack an adequate understanding of the necessary components, such as batteries, generators, electric motors, and modified turbo components.
You also mentioned that airports and flying-related infrastructure need to be further developed, too.
Hornung: That’s right. For instance, we are currently looking at ways to improve aircraft ground handling activities and their interaction with the terminals and the airport infrastructure. This also depends on future aircraft sizes. Another topic, in particular for megacities with ten million inhabitants or more, is how to get airports closer to the city center. Nowadays they are usually miles out of town, so most of the journey from door to door is spent getting to and from the airport. Yet in cities this size, ground transport is notoriously slow. Overall, this means that on shorter and medium-haul routes, flying is becoming a less attractive option. What can we do to change this situation? One key driver here will be noise reduction. Making aircraft quieter is the only way to increase acceptance for airports that are located closer to residential and business areas and can be reached more quickly.
Professor Dr.-Ing. Mirko Hornung
Professor Dr.-Ing. Mirko Hornung Executive Director Research and Technology, Bauhaus Luftfahrt e.V., and Professor of Air Transport Systems and Aircraft Design at the Technical University of Munich
Mirko Hornung (44) was appointed Chair of Aircraft Design in the Department of Mechanical Engineering at the Technical University of Munich in 2010. That same year, he also became an Executive Director of Bauhaus Luftfahrt. As a scientist and lecturer Prof. Hornung focuses on conceptual aircraft design, aircraft integration and evaluation. He studied and received his doctorate from the Department of Aeronautical Engineering at the University of the Bundeswehr (Federal Armed Forces) in Neubiberg near Munich. His dissertation on reusable space transport was awarded a research prize in 2003. Until 2009, he worked at EADS (now Airbus), where his responsibilities included the preliminary development of future air transport systems.
Wouldn’t one way of reducing noise simply be to develop aircraft that can take off vertically? Like the Harrier jet?
Hornung: The short answer to this is yes. But you can’t cheat physics. You still have to generate the thrust for vertical take-off, which produces a high level of local noise and also consumes significantly more kerosene than conventional takeoffs and landings. A vertical takeoff would have to be able to hold its own against present-day solutions in terms of both eco-friendliness and economic viability. For this reason, no one considers it feasible for the mass market.
Some of the concepts you are elaborating at Bauhaus Luftfahrt will never see the light of day—or at least not as originally intended. I can imagine this can lead you to question the point of it all.
Hornung: This is indeed a subject that comes up regularly. Our ambition is not to say this or that will or must be the next product. We want to explore new technologies and understand where their potential lies for air travel. We then communicate these findings. In this way, we create awareness for them and offer food for thought—outside a company’s normal development environment. Our job is to show that there are still a lot of issues in aviation that are as yet unresolved. But also that there are possible solutions out there.
Wouldn’t it be better for the companies concerned to find these solutions themselves?
Hornung: Testing out ideas within the company context is extremely difficult. As soon as you investigate a new technology and communicate it to the outside world, everyone jumps to the conclusion this is going to be that company’s next product. It’s actually a feasibility study, which doesn’t necessarily have anything to do with a product. You have to make a clear distinction. Something else we find time and again is that it is much easier for independent and autonomous research institutions to enter into dialog with sectors from which technologies could be adopted or modified. This is because such institutions don’t have a vested interest the way corporate entities do.
Devising innovative problem-solving approaches requires you to examine the issues from many different angles. Does this mean that Bauhaus Luftfahrt has to draw on a whole variety of experts?
Hornung: This is precisely what we do. We work with a really colorful mix of experts: social scientists, ethnologists, economists, geographers, engineers from various disciplines, physicists, analytical chemists. They all contribute their scientific expertise and their own perspective. This, incidentally, might initially have nothing to do with aviation. What they all have in common, however, is their ability to work scientifically, understand technologies, approaches, and theories in their own area of expertise, and transfer these into another context.
What does that mean exactly?
Hornung: The team analyzes social trends, socio-economic constraints, and scientific publications on new technologies. It then tries to understand and evaluate them, and examine what ramifications they may have on air transportation. For instance, what possibilities does a given technology with such and such core characteristics offer you? Is there a problem area in aviation where it could be meaningfully used to create value, provided it meets certain criteria?
So, on the one hand you have to think freely and creatively and recognize technological approaches and conceivable applications at an early stage. At the same time, you have to analyze what possibilities the current state of the art offers with a high degree of scientific accuracy …
Hornung: … and that’s precisely the challenge. I have to admit I’m constantly leaping back and forth between these two worlds. It’s one thing to have an idea—in a spontaneous creative process. It’s quite another to examine its plausibility and its potential; in other words to decide what you can actually do with it. That’s hard scientific work. It’s extremely challenging—but also very exciting.
Can you give us a current example?
Hornung: Energy recovery in engines using thermoelectric elements. We became aware of this technology some years ago and took a closer look. It was interesting, but very low efficiency ratios rendered it practically useless for applications in aircraft. However, our analysis did show that if such thermoelectric generators, which are capable of producing electricity from waste heat, were ever able to achieve higher efficiency coefficients, then things could get exciting. And this is exactly what has happened over the past few years. A recent study conducted as part of the German aviation research program has revealed that this method of energy recovery could in fact make a contribution today. You simply have to get over the “it’ll never work” mentality. Everyone said the Geared Turbofan™ engine would never work either. Too complex, too expensive. It’ll never be tenable; it’ll never be approved. Now we can see that it does work: it’s flying. So the barrier can be overcome.
In your example, developing those technologies until they were usable happened over a longer period of time. Isn’t it possible that one day aircraft might, after all, look very different than they do today?
Hornung: As I said, if a technology emerges that justifies a change, then yes. Electric or hybrid propulsion systems could bring about a dramatic change in an aircraft’s layout. But until then we still have to overcome considerable technological hurdles. Perhaps there are other technologies that we don’t even know about at the moment. But I can promise you one thing—we’re keeping our eyes peeled.
Founded in 2005 and headquartered in Taufkirchen near Munich, the non-profit association defines itself as an interdisciplinary think tank for the future of mobility and air travel. The association’s team of around 50 natural scientists, humanists, and social scientists elaborates comprehensive future scenarios and models for the European aviation industry. In this, it cooperates closely with industry and science—albeit independently and in the public interest. Bauhaus Luftfahrt is sponsored by the Bavarian Ministry for Economic Affairs and the Media, Energy and Technology, as well as by the Airbus Group, IABG, Liebherr Aerospace and MTU Aero Engines.