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Fuelless Flight with Air Submarine?
An anonymous reader writes "Using the same physics principles as submarines, a new company is planning a fuelless air ship. Recent advances in ultra light and strong materials are making this concept a practical reality." There's no question that changes in buoyancy can be used to propel a vehicle, but "fuelless" is going to be tricky.
already happened: see the gimli glider story
Nope.
Much older.
Carl Sagan, Robert Heinlein, Ray Bradbury, and a number of other scientists and writers were inspired by "The Martian Tales of Edgar Rice Burroughs". The first one, "A Princess of Mars" was published in 1912. (And it's on Project Gutenberg!).
In these books, John Carter was mysteriously transported to Mars, which was called Barsoom by the inhabitants. He became the Prince of Helium (a city/city-state -- not the element). The Barsoomian navies had huge airships that were held in the air by use of the 9th (or 8th?) light ray, so they needed no power to stay aloft. (According to Burroughs, we only know of 7 rays of sunlight, as seen in a rainbow, from red to violet, but Barsoomian scientists had isolated 2 other colors, never seen on Earth, and one of these colors is what gave light a repulsive power so it was repulsed from objects and reflected to our eyes, and it was used to keep the Barsoom airships in the air.)
The Martian Tales are far-fetched, but a ripping good time to read (at least the 1st 10 are -- skip the last one).
When I first read the story, all I could think about were E.R.B.'s descriptions of the huge naval vessels floating through the air of a dead planet (there were no sea going navies, since there were no seas, except one at the south pole).
Too bad these stories seem all but forgotten now.
The remaining engines will have to push harder to maintain speed but this makes the entire aircraft want to turn constantly. Very few runways come in corners.
IMAP (I am a pilot), losing an engine on a commercial plane is no big deal. Any asymmetric thrust is easily countered by the auto-pilot or the pilot by use of the rudders. Landing on one engine is also no big deal. The only issue is holding altitude while flying high, the plane might need to descend to 20,000 or so, then it can hold altitude (required to by the regs). Even loosing an engine on take-off is not a big deal. The plane must have enough speed before rotating (Vr) to maintain flight if one engine goes out.
The structural requirements of a vacuum are much greater than helium. The entire structure goes into compression and bending when in a vacuum, meaning it will need to be extremely strong in order to resist bending. This is a bit like sucking the air out of a 2 liter pop bottle, it will collapse easily, and the pop bottle will need to be substituted with a steel canteen in order to keep its form. Unfortunately, this kind of structure is heavy, and in terms of air ships are extremely inneficient.
A regular blimp inflates, so the forces on the skin are entirely in tension, the only bending forces are caused by loads the ship is carrying and more importantly, sudden wind gusts which could tear a weak ship apart. Structurally speaking, this is vastly more efficient and completely eliminates bending due to a vacuum, and the tensile force alone in the skin is often enough to provide a stiff but flexible frame, just like a ballon once inflated keeps its shape even under tremendous strain. It is a very resiliant structure.
There are two huge problems that have always existed with airships, and fuel is not one of them. The first problem is landing the craft. They have a tendency to blow around with even slight gusts of wind, and if anything happens like a downdraft, they can get smashed into the ground. The second problem is weather related. In violent weather, the thin skin on these ships can get torn easily. The larger the craft, generally speaking, the bigger the problems. This is not to say these problems are inherently unsolvable, but why bother using zero fuel when fuel already will cost next to nothing if it uses solar power or fuel cells.
Isn't that what the sci-fi writers of the 1940s/1950s thought the future would be like? After all, the Empire State Building has a blimp port at the top.
You're off by at least a few decades. The Empire State Building was built in 1930-31. The Hindenburg disaster in 1937 gave lighter-than-air travel a very bad reputation for the next few decades. Watch "Bright Eyes" (with Shirley Temple) and you'll see that heavier-than-air aviation was already glamorous. And by the 1950s, commercial transatlantic flight had become very routine (though expensive).
Incidently, the airport in the Empire State Building was not really well planned. One of the main selling points of zepplins was the ability to travel in comfort. To enter the Empire State Building from the top, airship passengers would have had to go down a gangplank in very high winds. It was an interesting idea, but the actual implementation was basically a scam.
Not that anyone ever actually follows a link and reads what is there, but I recommend that all the "non-believers" here take a look at Seaglider.
Or follow this google search for even more.
Seaglider applies much the same principles as this vehicle but to an underwater environment. It has a small onboard power supply, but it alternately uses gravity and bouyancy to propel itself.
I may not be an Aerospace Engineer but I am an Ocean Engineer and Fluid Dynamics in air is the same as Fluid Dynamics in water. Just change your value for rho.
The blimp thing. Blimps are basically oval balloons. They hold their shape because they are pressurized. (blown up!) as such the gas inside is under pressure, I imagine quite a bit ~5 lbs/square inch at least. This is in direct conflict with the goal of being bouyant, as pressurized gas is more dense.
On the other hand, this plane would be a rigid airship. It would hold it's shape regardless of pressure inside (within limits, too much or too little, pop or squish.) My point here is that comparing rigid airships to blimps in lifting volume is not that simple. Also, rigid airships can have much better areodynamics than blimps. Oh, and they do not constantly change shape. If you want to go higher, either have the gas bags inside only partly full at the fround (limits lift, does not waste gas) or add valves and vent it (limits range, cause you will not have enough lift when you decend again, unless you use ballast . . .)
I take this article with a large bucket of salt too, but not for any of the reasons you listed.
Laws are horrible moral guides, moral guides make even worse laws.