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Lighter Than Air
To change oh so slightly the topic from the doom and gloom of previous posts, here’s a bit of good news, unless you are DeAnander:
The Flying Taxi:
This was brought to my attention via an article in Le Monde, which is quite upbeat in the article.
Initially developed by NASA, the technology has recently been validated by detailed studies conducted by City University of London, which conclude that the "plane" could take off and land with only 125 meters of runway.
The concept is a low-altitude, low speed flyer (thus requiring no pressurization) which could be used on specific point to point lines (airport to city center, for instance). With a USD 1 million price tag, the "commute" could be affordable to a number of people, although it will never become a mass system of transportation…
Of course, the manufacturer, Avcen of the UK, has prepared a military version which is likely to be developed first…
Oh, well, the little boy in me can dream…
If I understand the linked page correctly, this is really quite a fascinating device. It doesn’t use gasoline, or any other fossil fuel. (Really!) It is possibly ecologically revolutionary, along the lines of “if there is still substantial public flight another century from now, this is what it will probably look like.” And no, it is not a perpetual motion machine. The concept behind a perpetual motion machine is that once you set it running, it will continue to run forever without any additional power. (Which is impossible.) This is a device for capturing free energy (in the form of heat) and converting it to motion. (Actually, to be more accurate, the device captures heat, converts it to gravitational potential energy, and then converts the potential energy into kinetic energy—motion.)
The key to the idea is that air temperatures are higher near the ground than they are at high altitudes. (Which is true.) Now, suppose you had a sealed balloon, inside of which you had some liquid with a boiling point of around, say, 75° F (~24° C) and whose gas form had a substantially lower density than air. On a day when the ground air temperature was higher than 75° F, the liquid would boil and change to a gas. Since the gas would have a lower density than air, the balloon would rise until the air temperature was lower than 75° F, at which point the balloon would lose its heat, the gas would condense back to liquid, and the balloon would fall.
This idea works like that, only with the added fillips that (1) you attach the balloon to a glider, so that once the gas condenses back into a liquid, you can control the direction of descent, and (2) you attach turbines to the glider, to convert some of the velocity into electrical energy. No gasoline actually required at all, during the flight! The tradeoff is that your flight path is not a smooth, fast curve, but rather a long, relatively slow, more-or-less vertical rise, followed by a long, relatively slow descent (possibly with additional rises and descents). You would still move much more quickly than you would on the ground, but at a lower speed than a jet airplane. (No more sonic booms—a definite selling point for me!)
The ecological price tag, as with a bicycle, is in the manufacture and maintenance of the device; at some point, energy is used to create the glider and the balloon, which has to be quite large to lift a bunch of people and/or luggage, and the liquid with the convenient physical properties. (The liquid is worrisome; it has to have a pretty esoteric makeup, and on the “no such thing as a free lunch” principle is probably heavily toxic, both in itself and in manufacture.) Still, from the basic description, I would suspect that the ecological cost of manufacturing the device couldn’t be more than that of manufacturing a normal small airplane, and the elimination of fuel would make it drastically better than a conventional airplane. (Plus there is probably a much lower maintenance requirement, although I may be mistaken on that.) Make no mistake: this is a technology to watch, and to suspend skepticism about until we know more—except for the bit about the military version coming first. (Grrrr!) Still, the idea is a genuinely clever and wonderful one, and my hat is off to the inventor!
Posted by: Blind Misery | Mar 3 2005 5:37 utc | 17
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