Will there be a return to elegance of flying?

The Demoiselle monoplane developed in Paris between 1898 and 1909 was called in its time the world’s most graceful, lightest and smallest flying machine. For its builder, the Brazilian-French Alberto Santos- Dumont, flying meant beauty and excitement, the absolute ideal. He is said to have become deeply dejected when he saw the First World War bombers and the destruction they caused. The collapse of his ideals drove him to depression and ultimately death.

No other form of travel has encompassed so many dreams and romanticism as the human aspiration to fly – it has turned up in dreams, ancient tales, religious myths and the psalms of the Bible. Finally it became a symbol of the technological revolution and illustrated humankind’s capacity to surpass its limits. A long-desired dream gradually became part of everyday life.

Then came the concern about climate change. Environmental organisations in particular have highlighted air transport as a symbol of a polluting way of life and as an accelerator of the greenhouse effect. Should we then draw back within our limits, give up our wings and the age-old dream to fly?

The world’s air traffic grows by 5–10 per cent every year, the strongest growth in air traffic being in the Far East. According to World Bank statistics, air transport passenger numbers increased by 28 per cent between 2003 and 2004. In the UK, passenger volume is forecast to double to around 475 million by 2030.

As traffic increases, the environmental effects of flying will also grow, as will pressure to limit them. Today air transport is responsible for around two per cent of carbon dioxide emissions caused by human activity and this figure is expected to rise to more than three per cent by the year 2050. In addition to carbon dioxide, air transport also generates other climate-warming emissions, such as nitrogen oxides, hydrocarbons and water vapour. It is also feared that in 2050 air transport will generate up to ten per cent of all climate-warming emissions of human origin. In the EU, aviation is the fastest growing emissions sector.

As air traffic has grown, specific emissions of aircraft, i.e. emissions per passenger and tonne kilometre, have fallen significantly – and this trend is expected to continue with the development of new technology. Despite this, the strong growth in air traffic will increase energy consumption and emissions worldwide. According to the basic scenario of the UN’s Intergovernmental Panel on Climate Change (IPCC), a six-fold increase in aviation by 2050 would caused a 2.7 times increase in fuel consumption.

But what will air transport be like at the end of this century, 85 years from now? Will there be less-polluting options available at that time? Will there be a return to elegance of flying? I believe so.

Air transport is, in principle, an extremely ecological way of moving around. It happens in the air, doesn’t take up land space, doesn’t weaken natural diversity, and doesn’t spoil valuable landscapes. And the worst aspect of land transport, moreover, is not necessary the emissions it produces. As the Finnish environmental commentator, fisherman and writer Pentti Linkola has stated: the worst thing is the asphalt that covers everything. In the air, on the other hand, there’s more than enough space.

Air traffic energy consumption and emissions can already be reduced in many ways using current technology. For example, with the aid of lighter materials it is possible to cut fuel consumption by up to 30 per cent from its present level. A foretaste of this is provided by the Airbus A350, which makes its maiden flight in 2012: a significant part of its load-bearing structures have been manufactured from composite materials, which make the aircraft lighter. As a result, the aircraft has lower emissions and is therefore more environmentally friendly than its predecessors.

In future, nanotechnology will present huge opportunities in the manufacturing of materials. Nanoparticles will make various surfaces extremely resistant to tearing and scratching, give long-lasting protection from corrosion, and improve the aerodynamic attributes of aircraft.

Computational flow modelling is already used very extensively in improving aircraft aerodynamics. As computing power grows, the utilisation of flow modelling will increase further, which should ensure that fuel consumption can be reduced by developing more streamlined aircraft.

In the aircraft of the future, wings will no longer be protruding appendages; they will be the most important component and will form the fuselage of the aircraft. An optimally bent wing frame maximises lift, reduces friction and significantly reduces the need for fuel.

Recyclable bio-based materials will be better suited to air transport fuel than in land transport, where enormous amounts would be needed to reduce emissions. For land transport there are better solutions to reduce emissions. It is entirely realistic to assume that at the end of this century, jet fuel (kerosene) will have been replaced with alternative fuels.

In future it will be possible to produce bio-derived fuels much more profitably and in a more environmentally friendly way, for example from bacteria or marine algae. Algae can double its biomass several times per day and it produces at least 15 times more vegetable oil per hectare than rapeseed, palm, soya or jatropha. Algae can be grown in seawater tanks, and no land or fresh water is needed to cultivate it.

In addition, it is possible to develop combinations of hydrogen and bio-based liquid fuels. One example of these is the H2CAR gasification process, in which biomass acts as the source of carbon in the biofuel and hydrogen is produced in a carbon-free way, for example by water, wind or nuclear power.

Qualitatively, bio-based fuels are, due to their clean combustion, better for engines than traditional fossil fuels. In gas turbine engines, fuel consumption can be reduced effectively by increasing the size of the fan, in which case air resistance can be utilised better in the combustion process. The US engine manufacturer Pratt & Whitney is currently developing largescale ‘turbo-fans’. By these an estimated direct fuel consumption saving of at least 15 per cent can be achieved – as well as an additional annual saving of one per cent when the fan model becomes widely used in the market.

It may be possible to discontinue using gas turbines completely. The options are, among other things, fuel cell technologies based on hydrogen, and solar- or nuclearpowered engines. Boeing is currently testing fuel cell technology in small aircraft, which it plans to introduce within 15–20 years. A plan exists to make a night-time, roundthe- world flight in 2009 with a manned aircraft, Solar Impulse, which is powered completely with solar energy. Nuclear-powered engines were actively tested during the Cold War, but their further development was restricted by the perceived accident risks. Development of safe nuclear engines has again been stimulated by the need to curb emissions.

Size is also a consideration. The size of aircraft can be increased to enable more people to be carried per flight, thus reducing the number of flights. On the other hand, it is possible to shift towards smaller aircraft which can use as an energy source lithium batteries or highly fuel-efficient turboprop engines. They consume considerably less fuel than jets.

The IPCC estimates that a worldwide rationalisation of air traffic control and routes could reduce carbon dioxide emissions by 73 million tonnes per year. According to the International Air Transport Association (IATA), saving one minute on flying times would reduce carbon dioxide emissions by 4.8 million tonnes per year.

The ways mentioned above present an opportunity to achieve significant reductions in air transport’s climate-warming emissions even in the near future. There is still a long way to go until zero-emission flying is achieved, however: the growth in popularity of air transport in particular presents a real challenge to emission-reduction measures, one that threatens to overwhelm the technical improvements. It is not realistic to assume, however, that the need to fly will be substantially reduced in the years to come. Virtual reality will scarcely replace face-to-face interaction – the human desire to see, feel and experience things personally. Fortunately enough.

I can imagine that, at the end of the century, aviation will begin to utilise more effectively the physical medium of flying – air itself. As the performance of computers improves, it will be possible to exploit more efficiently and in real time air streams and the winds that blow in the upper atmosphere. One of the most fascinating possibilities is the return of airships serving passenger traffic. Surrendering oneself to the air is the elegance of flying in its best.

The future of aviation may mean the abandonment of the Western concept of time: perhaps we will no longer fly according to the clock and timetables, but when it is favourable, inexpensive and sensible to do so.

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