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Dreaming of clean green flying machines

Dreaming of clean green flying machines

In common with many other corporate lobby groups, the International Air Transport Association publicly proclaims their commitment to achieving net-zero carbon emissions by 2050.1

Yet the evidence that such an achievement is likely, or even possible, is thin … to put it charitably. Unless, that is, major airlines simply shut down.

As a 2021 Nova documentary put it, aviation “is the high-hanging fruit – one of the hardest climate challenges of all.”2 That difficulty is due to the very essence of the airline business.

What has made aviation so attractive to the relatively affluent people who buy most tickets is that commercial flights maintain great speed over long distances. Aviation would have little appeal if airplanes were no faster than other means of transportation, or if they could be used only for relatively short distances. These characteristics come with rigorous energy demands.

A basic challenge for high-speed transportation – whether that’s pedaling a bike fast, powering a car fast, or propelling an airplane fast – is that the resistance from the air goes up with speed, not linearly but exponentially. As speed doubles, air resistance quadruples; as speed triples, air resistance increases by a factor of nine; and so forth.

That is one fundamental reason why no high-speed means of transportation came into use until the fossil fuel era. The physics of wind resistance become particularly important when a vehicle accelerates up to several hundred kilometers per hour or more.

Contemporary long-haul aircraft accommodate the physics in part by flying at “cruising altitude” – typically about 10,000 meters above sea level. At that elevation the atmosphere is thin enough to cause significantly less friction, while still rich enough in oxygen for combustion of the fuel. Climbing to that altitude, of course, means first fighting gravity to lift a huge machine and its passengers a very long way off the ground.

…click on the above link to read the rest…

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