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Green wing: can technology make flying more environmentally friendly?

By Paul Sussman for CNN
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(CNN) -- Next time you board a plane and jet off on holiday to somewhere hot, spare a thought for the fact that by flying there you are probably helping to make that somewhere even hotter.

The aviation industry has become a notable contributor to atmospheric carbon pollution -- pollution that is in turn helping to accelerate global warming and climate change.

Every day, according to the U.N.'s Intergovernmental Panel on Climate Change (IPCC), over 85,000 flights take off from airports around the world. Those flights burn 130 million tonnes of fuel annually, a figure that is projected to rise to 300 million tonnes by 2015, and 450 million tonnes by 2050.

To give a specific example, a single trans-Atlantic flight will consume a whopping 60,000 liters of fuel -- more than the average motorist uses in 50 years -- and add approximately 140 tonnes of carbon dioxide to the atmosphere.

Altogether it is calculated the aviation industry is responsible for 0.55 billion tonnes of CO2 pollution annually, some two percent of global carbon emissions.

While this is considerably less than the 18 percent contributed by the motor industry, the detrimental impact of even that small percentage is undeniable.

Nor is it simply carbon dioxide that is the problem. Air travel produces significant levels of other greenhouse gases such as Nitrogen Oxide -- 750 kilograms of it on the aforementioned trans-Atlantic flight -- while the damaging effects of those pollutants are amplified by the fact that they are being emitted at high-altitude.

Indeed IPCC scientists have estimated that greenhouse gas pollution from high-flying jets is up to four times more damaging to the environment than identical levels of pollution emitted at ground level.

Quantum shift

None of this is especially earth-shattering news. For over a decade the ecologically damaging aspects of flying have been acknowledged and publicized, and the airline industry -- partly of its own volition, partly under pressure from governments, green lobby groups and public opinion -- has taken significant steps to address the issue.

According to the International Air Transport Association (IATA) jet engines today are 40 percent more fuel-efficient than those designed in the 1960s, with pollutants such as soot and sulphur now almost completely eliminated from jet exhaust.

Carbon-emissions trading is becoming increasingly widespread within the industry, as is carbon off-setting, the latter involving passengers paying a voluntary surcharge to help finance the planting of trees or other green projects and so balance out the environmental damage caused by their journey.

Many airlines -- Virgin being one example -- are actively developing bio-fuel technologies in an attempt to reduce their reliance on carbon-emitting fossil fuels, while a great deal of work is being done in the area of improving air-traffic management.

In particular aviation planners are focusing on ways of cutting the amount of time planes spend queuing to take off and land, in the process burning large and unnecessary amounts of fuel (IATA estimates that airlines could cut their annual CO2 emissions by 12 percent if air-traffic control operations were more efficient).

While such initiatives are certainly helping to reduce aviation's environmental footprint, however, the rapid growth of the airline industry, with an ever-increasing number of flights catering to an ever-increasing demand for air travel, means that their impact is at best limited.

Many commentators are arguing that what is needed to tackle the problem are not simply measures such as those outlined above, but rather a quantum-shift in the technology of air travel, with a radical re-think not only in how planes are designed, but also what they are actually made of.

Only by re-configuring the technological basics, they argue, can the airline industry square the circle of meeting increased demand for air travel while at the same time reducing the environmental damage caused by such travel.

Laminar flow

What sort of technological innovations are being considered?

One area that is attracting an increasing amount of interest is "laminar flow control." This involves reducing the friction between the aircraft and the surrounding air, thereby lessening the plane's drag and making its fuel consumption more efficient.

For optimum flying performance the thin glove of air that hugs the surface of the aircraft should flow as smoothly as possible (something aeronautical engineers refer to as "laminar flow").

In practice, however, the air closest to the aircraft, especially around the wings, becomes extremely disturbed during flight. This in turn creates localized turbulence that accounts for up to 40 percent of the plane's drag.

To rectify this engineers have been investigating ways of improving laminar flow, with one idea being to install thousands of tiny holes along the aircraft's wings.

Fans within the wings would then suck the disturbed layer of air tight back against the wing surface, thereby restoring a smooth airflow and cutting drag by anything up to 20 percent.

A variation on this theme, first explored way back in the 1960s and pioneered more recently by U.S. commercial pilot David Birkenstock, is to combine a system of laminar flow control with modifications in the actual shape of the plane, specifically the substitution of the traditional tapered rear fuselage with one shaped like a cone.

Such a modification, combined with an effective laminar flow system, could, it has been estimated, reduce an aircraft's power requirement by anything up to 60 percent, with a concomitant reduction in fuel usage.

Flying wing

Revolutionary changes in fuselage shape are at the heart of another innovative technological option, the so-called "blended wing body" or "flying wing".

Here the alterations are more fundamental. Instead of the traditional cylindrical fuselage with wings extending off it to either side, the flying wing, as the name suggests, comprises two vast V-Shaped wings with engines, cockpit and cabin incorporated into them.

The design was actually mooted as early as the 1940s by U.S. aircraft manufacturer Northrup, and has already been realized in the field of military aviation in the form of the B-2 Spirit stealth bomber (Boeing are currently working with the US Air Force on a similarly shaped bomber, the X-48B).

Whereas military interest in the design has been driven by its radar-defying properties, it also has significant commercial possibilities due to its dramatic drag-reducing (and thus fuel reducing) potential.

Unfortunately the flying wing, as with a workable system of laminar flow control, is still a decade if not more away from achieving any sort of viable commercial application (not to mention billions of dollars of R & D investment).

A far more promising, short-term area of technological development, and one that is already bearing fruit, involves the materials from which aircraft are actually constructed. Specifically, the replacement of aluminum with lightweight composite materials such as plastic carbon fibre.

Composite materials

"Advanced materials are a huge issue in aviation at the moment, and have massive potential," Paul Everett, Director of Communications for the Society of British Aerospace Companies, told CNN.

"The advantage of such materials is that they are extremely light and thus substantially reduce fuel use."

Approximately 25 percent of the Airbus-380 is already made of composite materials, and it is estimated that percentage will rise to 50 percent for both the Airbus-350 and Boeing 787.

"This is a technology that is deliverable now and that will address a significant part of the polluting issue," says Everett.

"Within the next decade we could well see a 100 percent composite aircraft. It is a technology that will absolutely be the key differentiator for major aircraft programmes of the future, dividing those companies and countries that have the capability to employ it, and those that don't."

Technology clearly has a huge role to play in reducing the detrimental environmental impact of flying.

Despite that, there are many who argue that unless mechanisms are found to actually reduce the numbers of people who fly, no amount of high-tech innovation -- or, for that matter, carbon off-setting, carbon trading or air-management streamlining -- is going to genuinely improve the situation.

"We simply have to tackle the growth issue, "says Richard Dyer, aviation campaigner for Friends of the Earth.

"To its credit the aviation industry is making improvements in technology and efficiency. Unfortunately, however, those improvements are far outstripped by the increase in air traffic.

"Until we find a way of reducing demand, most of the environmental problems associated with flying are going to remain unresolved."


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