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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.
Zero weight isn't quite the same as zero inertia. You don't see the Goodyear blimp flipping around at football games.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Fish, hot air balloons, blimps, even the float in my toilet relies on buoyancy. Do you even know what buoyancy is? While you're at it, look up submarine. Here's a hint: sub-marine.
It's a stupid name. Period.
No - it's not a scam nor perpetual motion machine. A company has already built submarines on this principle that are being used as autonomous research drones. Here's announcment about the Slocum Glider. Here's a couple of action shots of it being deployed. My advice would be to talk a couple of college physics courses to undertand how BUOYANCY works.
Granted it's more complicated in air (larger because air is so dilute when compared with water) however with advances in composite materials, it is certainly doable.
Thalasar
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
I really don't want to sound like an Anime Fanboy here, but you might like to check out Last Exile if you haven't already seen it. It's a decent little series with some really impressive graphics, built around exactly that kind of concept...
Yes, I remembered that book from years back, as soon as I saw the article. Interestingly, Aereon Corporation is still in business after all these years. Check it. . .
http://www.aereoncorp.com/
The page about the Aereon III is especially interesting.
These ships were based on the theory that a lighter-than-air craft could "glide" upwards, then vent some gas and glide downward, then drop some ballast and glide upward again, and continue in this manner until it ran out of gas or ballast. It's all about using aerodynamics to translate the up-and-down movements into horizontal motion. It's not a perpetual motion machine.
A nifty and clever idea, but one of dubious practicality.
Since buoyancy is caused by gravity pulling the fluid (air/water) around you toward the earth and you moving away from the earth to take its place. "Form of gravity" is probably a less accurate term than "effect of gravity." Still, Stephen J. Mraz was right, you're wrong. How about that severe beating?
Nothing bothers me more than shitty pseudoscience.
Be careful when you deride things you don't understand. This isn't new technology. It's been in use in autonomous submarines for years. Employing the same principles in the air hasn't been done yet because it's a bit more complicated: The speeds are a lot higher, the weather becomes a factor, and the margin for error is a lot smaller.
"With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea...."
RFC 1925
I sure hope you're joking. This design relies on a surrounding fluid that is more dense than the craft itself to keep it aloft - it floats in air as a balloon does. You can't *float* in vacuum.
The bouyancy pumps on a sub are one of the smallest power loads. Most WWII subs had hand pumps connected to the ballast pumps.
True.
But they also used their diving planes mostly to convert forward motion (from those BIG engines) to vertical motion, rather than the other way around. They did most of their diving that way, and used the bouyancy adjustment mostly to hold themselves at a particular depth or the surface.
Except for coming up suddenly, of course. In that case they discharged an ENORMOUS blast of energy in the form of compressed air into the bouyancy adjustment. (It takes a LOT of power to compress air.) They could make that up slowly over a significant period of time, so the load on the diesel was small compared to cruising friction.
But if they had propelled the boat by running it up and down repeatedly and converting that to forward motion via diving planes, like the "submarines" described in the original post, and intended to make significant progress that way, they'd have needed an amount of energy similar to that needed for the electric motor driving the prop when submerged to achieve the same speed.
Bouyancy adjustment drive has the advantage that it doesn't require external rotating parts, to leak, become fouled or corroded, etc. (You can even do away with diving plane adjustments by flipping the craft, accomplishing this by redistributing internal weight.) This is very handy for long-term, great-depth devices which aren't in a hurry to be somewhere else.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
As an aside, 1 cubic meter of helium provides about 1 kg of lift (bouyancy). Hydrogen is only slightly better at about 1.2 kg per cubic meter.
So, if you want to hover a modest size craft (say 1 metric ton or so, which is rather small), you need to use about 1000 cubic meters of helium. Which is a bag 10 meters per size. Not a chance in hell for his design.
For example: a modern 737-800 aircraft weighs roughly 40 MT empty, has a cabin size of 40m long by 3.5m in diameter, and has a maximum cargo weight of about 30MT. Given that you can reduce the craft weight by 75% with advanced materials (very optomistically), you still need a gas volume of 40,000 cubic meters to lift the craft and cargo. This occupies a space 104 times the main cabin volume.
So, who is he trying to bullshit?
-Erik
There are always four sides to every story: your side, their side, the truth, and what really happened.
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.
I didn't see any references to the efficiency of the turbine, but I doubt he's claiming they are 100% efficient. In fact, in one paragraph, he points out that if the turbines didn't manage to regain enough energy to compress the gas, the plane could be landed and pointed into the wind, and thus recharge itself.
The wind is thus input, and it isn't perpetual motion.
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.
WWII subs are not a good example because they didn't dive very deep, and they were diesel powered, meaning they couldn't stay submerged very long on battery before they were forced to surface to run their engines.
:). In particular "hover mode" cycles a shitload of water per second (that's the highly specific non-classified term for you). The purpose is to create a very stable platform for launching weapons, missiles, whatever, with no forward motion.
Modern nuclear subs actually do put a lot of power into buoyancy adjustments, and yes that's the correct spelling
Without either forward motion, or hover tanks, standard buoyancy adjustments would not keep the ship stable and it would tend to tilt one way or another, especially after launching its payload.
Standard buoyancy adjustments aren't nearly as power intensive, but they are used more often than in WWII, since subs now dive very deep and may have to adjust for thermal layers and other ocean / weather events.
The plane adjustments are used differently depending on the desired effect. The stern planes adjust the orientation of the ship, while the bow planes allow you to move up and down without tilting much. This is important with subs nowadays because of their sheer length. One degree of tilt could put you at 7-10 feet of difference from bow to stern, which is a big deal when you're at periscope depth and don't want to breach.
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.
I totally agree. I'm not an aerospace engineer, but this seems like a complicated perpetual motion machine to me.
In much the same way that moon oribting the earth is a perpetual motion machine. In theory, this could work if the energy needed to fill/evacuate the air bladders is lower than the energy that the turbines can create during descent. Working much like regenerative braking, the idea is to turn the change in potential energy states, into usable energy.
My question is how much mass can it transport while still maintaining some level of that efficiency? It has to descend fast enough to power the turbine, overcoming the 'fixed' startup energy costs and the inherent conversion inefficiencies, and then use that to run the pumps.
Any takers on the Math? I've slept since then...
The real danger of this is not crashing, it is that if it runs out of energy to compress air, it will float up out of the atmosphere and vanish into outer space, with everything and everybody aboard!
Laugh while you can, monkey-boy!
The inherent problem with airships is that the huge surface area combined with low weight means they get blown around easily and handle badly. Adding wings doesn't help. It's been tried. Adding power does help. Adding steerable power helps even more.
For an idea of what a successful modern lighter-than-air craft looks like, see Zeppelin Luftschifftechnik GmbH, which has built several large rigid airships in the last few years. But even with carbon fibre and Kevlar, the load capacity is small.
i do not believe that the claim is being made that this is a perpetual motion machine - only that it would require vastly less energy than current technology based upon fossil fuels.
remember conservative fields? there is no net loss/gain of energy. in this case gravity is the conservative field.
now TRUE, there should be some small loss of energy due to friction, BUT the idea is to use some of that to restore the buyancy. if there is an additional wind present relative to it's trajectory then it might make up for this frictional loss of energy, and infact then the net consumption of energy would be zero (altho there would be other things like onboard electronics, and so forth that would consume energy also).
If your craft is dependant on creating a vacuum inside for easy lift, but your power supply is compressed air, don't the two kinda cancel eachother out?
Not at all. The craft rises when its average density is lower than the air around it. When the compressed air is in its compressed form, it takes up little space. When it is used to blow up the balloon, the mass stays the same but the volume increases by a *lot. Hence, the average density is much lower.
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.
I'm sure some of you are breaking out your ideal gas law to see if this is a perpetual motion machine. However, please take this into account: buoyant acceleration is actually = g*(m-md)/(m+md) where m is the mass of the buoyant object and md is the mass of the diplaced gas.
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.
Sounds a little like Tom Swift's Paraplane (which used an external gasbag) from Tom Swift and His Electronic Retroscope, Grossett & Dunlap, 1959.
Aside from perpmo in general, using stored compressed air to power the compressors to gather more compressed air? That was iterated at least twice. The Engineer in me would not tolerate a second audition for an exact count of banal pseudo-scientific nuggets...that one is a deal killer all by itself.
"If no one tilts at windmills, the damn things will take over the world!"- christian simpleman
On the 10th of February 1972, in New Scientist magazine, Daedalus proposed a similar scheme, using ammonia as the working fluid:
"... one might think, a balloon filled with ammonia would rise rapidly to 25,000 feet, and then lose lift by the liquefaction of its gas."
"... overcome this by putting his ammonia in a somewhat elastic balloon which will always squeeze it to about 0.1 atmospheres greater pressure than the atmosphere outside. This will raise its condensation-point sufficiently for the ammonia to liquefy at about 34,000 feet."
It seems that someone has been taking Daedalus seriously, but when they did the math, they found that the ammonia was a bit troublesome, and they now seek to do without it.
You can read a copy of the original Daedalus column in "The Inventions of Daedalus: A Compendium of Plausible Schemes" by David E.H. Jones, W.H. Freeman & Co 1982. ISBN 0-7167-1412-4.
Regards.
Six boxes to use in the defense of liberty: letter, soap, ballot, witness, jury, ammo.