Fuelless Flight with Air Submarine? 428
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.
Holy *hit BatMan (Score:2, Redundant)
Re:Holy *hit BatMan (Score:2, Interesting)
Yep... (Score:5, Funny)
Actually it is safer (Score:5, Interesting)
Loosing power on only one side is not a picnic even. 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.
Gliders on the other hand are designed to ehm well glide. This thing would never suffer an engine failure. Power system (it does have one) fail? Simply glide gently down giving you a far wider range in wich to find a suitable landing splot.
There are many reasons this can fail but worries about safety because of a lack of engines ain't one of them . Note that it isn't a balloon. With wings that size it could exchange hight for speed and with that control over its direction.
Re:Actually it is safer (Score:5, Informative)
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.
Best. Typo. Ever. (Score:5, Funny)
Another Huntism... (Score:3, Funny)
"A conventional glider is towed to fairly high altitude by an airplane or is launched by a tow wench."
That must be one really big mama. The "Attack of the Forty Foot Woman" comes to mind.
Oh, maybe he meant "winch".
Re:Actually it is safer (Score:5, Funny)
If Kurt Russel and Harrison Ford can land a 747 with one engine dead and one burning, then so can I. How hard can it be?
Re:Actually it is safer (Score:4, Insightful)
I rember a story about a Canadian 767 that ran out of gas and was lucky enough and had a very talented crew that managed to glide to an old airfield and made a dead stick landing.
Re:Holy *hit BatMan (Score:5, Insightful)
Of course that is the intent. Their perpetual motion is a complete farce. If you listen to the explanation (I know, it's ludicrous) they're basically saying you can get more air going down then you can going up.
Some other fallacies is the "lighter than air" effect. If you've ever seen a blimp, then you realize the size this craft would have to be in order to carry even the lightest loads. Helium is only "lighter than air" when it's density is lower. This is the whole "which weighs more, a pound of lead or a pound of feathers" argument.
Along those lines, you'd also need to take into account the expansion effect. Let's use weather balloons as an example. The higher they go, the bigger they get. Air pressure drops as you go up, therefore the greater air pressure in the balloon expands it outward. If it didn't, then the balloon would reach an equilibrium and go no higher. This craft would need to also take this into consideration. This could be quite a technical hurdle, gliding an aircraft that is constantly changing dimensions.
Regardless, the craft would at least need to carry some onboard power source.
I take this "article" with a big salt lick.
~X
Random Quote:"If it's too good to be true, then somebody is getting rich and it isn't you."
Re:Holy *hit BatMan (Score:5, Informative)
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.
You're right about the size (Score:3, Insightful)
It's also a rigid ship, the gas bags are inside a rigid frame. The frame used to be aluminium but they'd use carbon fibre these days. Buoyancy bladders are not a particularly big hurdle.
It's all technically possible but I'm not convinced it'd be what you could call quick.
1940s vision of the future coming to life? (Score:5, Interesting)
Re:1940s vision of the future coming to life? (Score:5, Funny)
The B-25 bomber [withthecommand.com] valet parking didn't work too well either.
Re:1940s vision -- Try 1912 vision by Burroughs! (Score:5, Informative)
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.
Re:1940s vision -- Try 1912 vision by Burroughs! (Score:4, Informative)
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 [lastexiledvd.com] 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...
Re:1940s vision -- Try 1912 vision by Burroughs! (Score:3, Funny)
Funny once, Mike.
Re:1940s vision of the future coming to life? (Score:4, Informative)
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.
Uh, Submarine? (Score:5, Funny)
Re:Uh, Submarine? (Score:3, Funny)
I don't think we really have to worry about naming this thing though. It's pretty obvious vaporware.
Re:Uh, Submarine? (Score:5, Interesting)
Note one line from the presentation: "gliders have glide ratios of up to 60 to one, and aerostatic balloons have been known to reach altitudes of up to ten miles" (don't know if I got the figures right). That's like saying, "Sports cars have been known to reach speeds of 200+ mph, and bicycles don't require power. Therefore, my hybrid has both qualities."
I'll ask around, but for now I'd call this an interesting way to part an investor from his money. Con artistry is the only truly perpetual motion I've ever heard of.
Re:Uh, Submarine? (Score:5, Interesting)
During flight it will probably regain a percentage of that power from decents, and use that energy to try and create the vacuum again to rise again. This won't be a perfect process, energy will be lost/wasted, so without external input it would eventually need to land. However, It will be receiving external input, mainly solar power. Not directly mind you, but the air currents created by the sun that will work to raise the plane (same way birds can glide for an extended period without flapping their wings). This external input disqualifies it from being a perpetual motion machine, but could allow it to fly for unseemly amounts of time.
Re:Uh, Submarine? (Score:4, Informative)
The wind is thus input, and it isn't perpetual motion.
Re:Uh, Submarine? (Score:3, Interesting)
I am taking this with a big grain of salt, but I would love to see a carbon fiber ball that is lighter than air due to the vacuum inside.
I say this is the acid test.
Also, Mylar is a great helium holder but I don't think it is good enough to hold u
Re:Uh, Submarine? (Score:5, Funny)
The answer's obvious. Why of course it'll have oars - manned by passengers flying coach. They're just omitted from the initial artist's conception.
Re:Uh, Submarine? (Score:3, Informative)
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 transpor
Devices that are wind powered. (Score:5, Interesting)
But what I don't understand is why he doesn't just create a giant inflatable airplane hybrid, that would probably work better. It could get 90% lift from helium and 10% from forward movement from a turbo fans powered by solar power. The helium ballon aspect of it could be the structural system as well, it would be an active system (inflatable), rather than a very heavy and expensive rigid frame.
Re:Uh, Submarine? (Score:4, Funny)
KFG
Re:Uh, Submarine? (Score:3, Interesting)
Supermarine History [shanaberger.com]
KFG
Re:Uh, Submarine? (Score:3, Informative)
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.
Re:Uh, Submarine? (Score:3, Funny)
odd, when I think "buoyancy", I think BOAT.
You know, that thing that every country or civilization that has ever come across water invented?
Oh, and FYI--Submarines have a lot to do with buoyancy. It's how they ascend and descend.
Re:Uh, Submarine? (Score:3, Interesting)
That is part of why I think "buoyant airship" would be apropos
Coming Soon! (Score:5, Funny)
Re:Coming Soon! (Score:5, Informative)
OT: Read it. Full of lessons. (Score:5, Insightful)
Lessons: a triple-check doesn't help you if there's a systematic error. Standardized measurements are a Good Thing.
>the EICAS issued a sharp bong--indicating the complete and total loss of both engines. Says Quintal "It's a sound that Bob and I had never heard before. It's not in the simulator."
Lesson: in a safety-critical system, train the users for "impossible" situations.
>Hydraulic pressure was falling fast and the plane's controls were quickly becoming inoperative. But the engineers at Boeing had foreseen even this most unlikely of scenarios and provided one last failsafethe RAT.
Lesson: when your engineers go paranoid, if there are lives at stake then for God's sake listen to them. "Belt and suspenders" engineering saved lives in this incident.
>Quintal "got busy" in the manuals looking for procedures for dealing with the loss of both engines. There were none..
Lesson: learn from experience. There have been incidents, like volcanic ash injection, that have forced shutdowns of all engines on a jetliner. If your statistics say the engines can't fail at the same time, and the graybeards say they can, then you left something out of the statistics.
>The avoidance of disaster was credited to Capt. Pearson's "Knowledge of gliding which he applied in an emergency situation to the landing of one of the most sophisticated aircraft ever built."
Lesson: there is no substitute for a wealth of experience. Downsize your 20-year veterans to save money, watch things go wrong.
Sorry for the diversion, but these are things I'm passionate about.
Prior art? (Score:5, Funny)
Isn't a fuelless air submarine usually called a "balloon"?
Re:Prior art? (Score:3, Insightful)
site design (Score:5, Funny)
Re:site design (Score:3, Funny)
Does this mean a sequal to down periscope? (Score:2)
Ugh.
U-571, will now be A-571.
Hmm.
No fuel? You still need power. (Score:5, Insightful)
All the same, it's still a cool idea. I want a small one to fly to work in (maybe add pedals for all the compression-> decompression stuff and you'll have a human powered plane ;)
Re:No fuel? You still need power. (Score:2, Insightful)
Re:No fuel? You still need power. (Score:3, Interesting)
Practically? I am really skeptic. Gut-feeling tells me that the turbine-battery-compressor cycle is not efficient enough for self-sustained propulsion.
Disclaimer: IAAEP (I am an experimental physicist)
IAAME & this violates the laws of TD pure & (Score:3, Interesting)
In order to recover all of that energy you must transfer ALL of it back into the compression of the hydrogen. This is impossible as there are NO 100% efficient "wind turbines" to recover that energy.
Forget about the fact that the plane glides forward - that's just smoke and mirrors. Look at the simpler case where the
This idea has problems (Score:5, Informative)
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.
Lightning (Score:3, Interesting)
I've heard that there's a really bad problem from lightning strikes if you plane isn't made from an excellent conductor like metal. Various attempts have been made to make non-metal composites that don't get badly damaged by a strike. If this plan goes really high then this will be a problem.
Can some engineer tell me, have they solved this problem or is this idea just hot air?
tanstaafl - you got to start somewhere... (Score:5, Insightful)
However, just because it may not use fuel to continue on it's journey doesn't mean it didn't need some power to get it started...
Physics 101. Law of thermodymanics. Etcetera.
Actually (Score:4, Insightful)
That would be the helium in this case. You could argues that it takes energy to build the thing, during which contained energy would be loaded via fuel powered vihicals, but thats a little overly semantical.
I mean, I can fill a ballon with helium, and it will rise without power.
Re:Actually (Score:5, Interesting)
But you can't come back down again unless you compress the helium (which takes work). You could jettison it, but then you'd have to do work to get more helium.
This scheme sounds a bit too much like a perpetual-motion machine. He talks about using energy generated by a wind turbine driven during the glide to alter the buoyancy... IF he'd talked about using, say, solar power to do so, I might believe this was something that at least didn't violate the 2nd law of thermodynamics. But he appears to be claiming he needs no external energy input. That's total crap, and I'm surprised more /. people haven't jumped all over that point.
I mean seriously, didn't anybody take intro phyics in school? If you learned nothing else, you should have learned that you can't get something for nothing. Anybody who says otherwise is selling something worth nothing.
Re:Actually (Score:4, Insightful)
Re:Actually (Score:3, Insightful)
So does sailing. But you are at the mercy of the winds.
remember conservative fields? there is no net loss/gain of energy. in this case gravity is the conservative field.
Yes, I know that you can move perpendicular to the gravity vector without doing any work, but that isn't really what he's proposing. He is going up and
This sounds to me (Score:2, Funny)
Impossible? (Score:3, Funny)
Well, in any case, you might want to get an Immortality Device [alexchiu.com] before you board one of these things.
Re:Impossible? (Score:3, Insightful)
Re:Impossible? (Score:3, Insightful)
Re:Impossible? (Score:3, Funny)
They store that increase in entropy down at the hydro/solar plant
Another improvement (Score:4, Funny)
Another name... (Score:5, Funny)
The only thing necessary for Micro$oft to triumph is for a few good programmers to do nothing". North County Computers [nccomp.com]
Hmm... (Score:5, Insightful)
"We humans can rarely invent any process that nature does not already use. Most of the science we know today merely copies nature. Our thermodynamic laws were formed by observation of nature. They are not proven, merely not disproved. Within this section of our website you will be taught a new science that mimics the earth's weather, by harnessing the dual forces of gravity -- buoyancy and gravity acceleration. Harnessing gravity may be more technically described as the science of harnessing mass differentials. High density mass falls within a low density lifting fluid, like rain falls from the sky, and low density mass rises in a high density lifting fluid, like a bubble rises in water or helium rises in air."
I think I understand the technology he is proposing (I'm confident it still requires input energy, beyond the environment), but he really should tone down the quack-o-meter. I think we can rest easily that the thermodynamic laws are intact.
-Sean
Re:Hmm... (Score:4, Insightful)
Lets start with the wheel.
Tumbleweed. (Score:5, Funny)
next!
Re:Hmm... (Score:4, Interesting)
Seriously!
No PhD here, but when someone's rambling on for paragraph after long repetitive paragraph about how buoyancy is related to gravity, and never really gets around to a precise description of what the heck this technology is, and keeps referring to "my invention", and alternately refers to himself in the first and third person, this registers pretty high on my BS-o-meter.
I couldn't stand to read too much of it, so maybe I missed something, but this really comes off (to me) as someone who's living in his own little "I know better than all those scientists!" kind of world.
He also talks about building a "cheap" $200k model that works in water in order to prove the airship technology, because it's somehow impossible to build a small-scale model that works in air. I don't think he's thinking too clearly abou this; you can certainly build a cheap model -- just don't expect it to carry people!
Fundamentally, it's still a good idea -- along the lines of the Mars Balloon, and the underwater gliders. But unless he's drawing energy from temperature differences at different altitude, solar heating, or some such, I don't see it working. Trying to get all the energy you need from turbines on the wings is definitely perpetual-motion-machine thinking.
Aaaaarghhhhhhh! (Score:3, Interesting)
This thing is supposed to fly because of a combination of reduced bouyancy (by way of creating multiple vacuum's inside it) and stored energy (by way of a turbine invented by the apparent author).
The turbine is for compressing air, to be used as power storage. I think.
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?
Even if you made it and got it up, what would it be like to try to control a zero-weight plane with mass? I picture it flipping around in the wind like a feather...
Re:Aaaaarghhhhhhh! (Score:4, Informative)
WTF!? (Score:3, Interesting)
Stephen J. Mraz, "Senior Editor," is in need of a severe beating. Since when is buoyancy "a form of gravity?"
I stopped reading there. Nothing bothers me more than shitty pseudoscience.
Someone wasn't paying attention in Physics (Score:4, Informative)
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.
RTFA (Score:3, Interesting)
Practicality of the design? (Score:5, Interesting)
The gravityplane must be very large in order to be lifted by a lighter-than-air lifting gas such as helium that provides a very low amount of lift, thus a small gravityplane can never be built and models of the craft will always be very large. However, a scale model of the gravityplane can be built as a sea glider that is less than 30 foot long that will be capable of holding four passengers. The sea glider can work in water at this small size, because water has a lifting capacity 821 times greater than the lifting capacity of air (62 pounds per cubic foot lifting capacity for water and
If at 30 feet a gravityplane can hold 4 passengers, could this design ever provide a viable means of transport for larger groups of people?
30 feet/4 people = 7.5 feet/person
Thats approx 75 feet per group of 10. Makes for quite a large plane for even medium sized groups.
For cargo I suppose this could be cost effective depending on the maintenance costs and its lifetime. Lets assume that an average person weighs 200lbs (I know it may be too large, but to allow for an optimistic view of the plane's carying capacity).
7.5feet/200lbs ~= 1foot/26lbs
May be good for cargo because shape, size and conditions don't really matter.
Re:Practicality of the design? (Score:3, Interesting)
Simple, scale the plane differently. Making the lifting bodies wider/taller to make up for the length. But secondly, what's wrong with a long plane? This thing's gonna be a pretty slow mover (glider; no forward propulsion), so it
you're forgetting (Score:4, Insightful)
I'm too lazy to do the math, but a longer body would have a far larger volume in the lifting body than liner.
7.5 ft per person on a 30ft version != 75ft for 10 ppl.
Re:Practicality of the design? (Score:3, Insightful)
Perpetual motion machines don't work (Score:3, Funny)
Old Navy joke? (Score:5, Funny)
That reminds me of the old joke back in the Navy... I think it went: There are more airplanes in the oceans than submarines in the sky.
I guess that's no longer true. :-)
Uhhh, hmmm... (Score:5, Funny)
What's scarrier, flying without an engine, or that the general public won't think twice about this sentence?
ObSimpsons (Score:3, Funny)
Perpetual motion machine alert! (Score:5, Insightful)
So far so good.
The new hybrid "gravity-powered aircraft"
Starting to get bogus.
is formed by merging the capabilities of the following devices into a single new aircraft apparatus:
(1) an aircraft capable of aerostatic (lighter-than-air) lift to gain altitude; and,
Still OK.
(2) a glider aircraft capable of aerodynamic lift, having a high glide ratio to accomplish long range gliding; and,
Starting to get bogus.
("Glider"? Using diving planes to add a significant forward component to upward/downward motion is well understood. But a "glider" is something else - a high-speed device with significant aerodynamic lift - initially powered by atmospheric thermal energy in the form of updrafts storing energy by raising a NON-bouyant craft against gravity, then trading this stored energy for momentum as necessary by gliding downward. Raising a neutrally-bouyant object stores no energy.)
(3) a (patented, new design of Robert D Hunt) wind turbine that is capable of harnessing the force of wind to generate power as the aircraft glides downward. This cycle can be repeated indefinitely to allow the craft to stay aloft virtually forever.
Bingo! Perpetual motion.
You CAN get a lot of forward motion out of lift-driven vertical motion. But it takes ENERGY to adjust the lift. The submarines described in the original Slashdot posting are one example. Zepplins with diving planes that achieved speeds in excess of 200 MPH by this mechanism also existed in the mid 20th century.
But the Zepplins BURNED FUEL to change their bouyancy (by heating some of their bouyancy gas), just as the submarines use energy to compress or expand gas in their bouyancy tanks. This makes them a heat engine (though a slowly cycling one) and subject to the carnot cycle limit.
This craft proposes to use a turbine to collect energy from the wind of its passage and use that to adjust its bouyancy, use the bouyancy to produce forward motion, creating the wind to drive the turbine. Like a generator with its shaft connected to a motor which is also wired to its output, the energy goes around and around, with some being lost in every pass.
This is not to say it won't fly at all. But to the extent that it DOES fly it's getting its basic power from vertical air currents, just like any other glider. By being nearly neutrally bouyant it sacrificed the ability to store energy in the gravitational potential of its own weight at altitude, and it's replacing that by being able to convert the wind of its passage to stored electricity, then feed that back into forward motion via bouyancy adjustments rather than propulsive fans.
But I expect this to be more expensive and less efficient than other alternatives - such as an equivalent modification to the original 200-MPH zepplins WITHOUT the fixed wings.
Re:Perpetual motion machine alert! (Score:4, Informative)
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.
Re:Counterargument (Score:4, Insightful)
The followup poster has exposed an error in the above, (though not the one he thought.)
Actually, as long as you compress and expand gas adiabatically, then the Carnot cycle is irrelevant.
Actually, adiabatic expansion and compression are two of the four cycles of a carnot engine. (The others are adding heat to the compressed gas at constant volume and removing it at constant volume.)
My carnot cycle argument applies to the case of the mid-20th-century airships where the bouyancy was adjusted by heating the gas. It IS irrelivant when you're adjusting the bouyancy by, say, using an electric motor to compress it into a tank. (Though other heat engine arguments do apply. See below.)
The conservation of energy argument also applies. I'll show you where the detailed physics of the process make it show up when we get a little further along.
Obviously you cannot make an engine that works in this way [losslessly], because the point of an engine is (1) to do net work or (2) to cause a heat transfer. So the efficiency of any engine cycle has a Carnot limit.
Right.
But the process you have described need not be an engine. In fact, this should be completely obvious. Since there is no net work being done, and no heat transfer, how on earth can you even define an thermodynamic efficiency for the cycle?
Even the process of compressing and expanding the gas makes this into a heat engine. Compressing the gas heats it. The heat must be dumped. Expanding the gas cools it, and heat must be applied from an external source to bring it back to temperature.
This doesn't make carnot apply, though. But it DOES lead to additional losses if you don't do your compression and expansion adiabatically.
You must compress slowly, and dump the resulting heat without forcing it across a significant temparature difference. Similarly you must scavange the energy when it expands by running it through an airmotor to extract the energy and recharge your energy storage. (Otherwise the energy gets dumped.)
But the temperature change takes place in the compressor/airmotor. This makes it very hard to add or dump the heat across negligible temperature gradient in order to perform the operation adibatically.
(You also get losses in the generator/motor/battery system, or whatever you're using to store the energy for reuse. The total of these losses is so high you're probably ahead to do the bouyancy adjustments with heat in the first place. But then you ARE a carnot cycle heat engine.)
All of the above are efficiency issues, however. They represent precentage losses of useful energy as it it transferred from one form to another (gas pressure, temperature, height of mass in gravity field, momentum, etc.)
You ARE an engine, by the way, because you're doing work: Lifting and lowering the mass of the vehicle, driving the vehicle against air resistance.
And you don't even need to get this complicated. (Slow) compression and expansion of an isolated volume of a gas is reversible and adiabatic. Hence it is isentropic.
Right.
But that doesn't mean the total cycle is reversible.
In the airship case, the compression occurs when the ambient pressure is low, and the expansion when the ambient pressure is high. Even if your compressor/airmotor was perfect, the difference represents a loss of energy - specifically, the energy necessary to raise and lower the vehicle, which is lost to air friction from the vehicle's motion. (Thus conservation of energy is not violated.)
So why not just use a propeller?
If you're heating the gas to adjust the bouyancy, on the other hand, you ARE a heat engine. So you don't beat carnot, (and have to input maybe three or more times as
Segway-style hype.... (Score:5, Insightful)
Honestly, after reading this site, it smacks of all the hype around the Segway (and many similar, less-successful "revolutionary breakthrough" schemes).
Yes, it is possible to create a fuel-less aeroplane that can still maintain forward motion. Advanced glider technology certainly fits this description. However, there are a couple of things that are missing from the adware:
The physics of underwater motion are similar those of flight - basic fluid dynamics here. The problem is he's ignoring fundamental environmental differences between water and air. The density differences between the two make it possible to move large masses underwater, but only tiny masses in the air using the same principles. Not to mention that the fluid consistency and motion between air and water are radically different, which invalidates using the ocean as a model for the sky.
He's a fraud. Pure and simple.
-Erik
Re:Segway-style hype.... (Score:3, Informative)
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 o
Re:Segway-style hype.... (Score:3, Insightful)
Yes, he talks about a balloon-like structure. More specifically, a Zeppelin-like structure, with a rigid airframe holding the lighter-than-air gases. However, the design is of a plane-like glider. Take a look at a modern zeppelin. The radio of volume to surface area is many times greater than what he's proposing. Essentially, he's using lifting gases to enhance the performance of the craft. No matter what he's building the craft out of, it won't be able to hover on lift-gas alone, given his design.
The bot
Also for sale... (Score:3, Funny)
$500,000.00. neg.
I accept PayPal.
Um ... Perpetual Motion anyone? (Score:3, Interesting)
I'd be curious to hear if anyone in any of the fields of physics, materials sciences, or aviation would like to offer why this is bordering on revolutionary brilliance, or why this is a totally unmitigated crock of sh--.
Peace.
No Fuel means no go (Score:3, Insightful)
website looks like Heaven's Gate (Score:3, Insightful)
The Deltoid Pumpkin Seed (Score:3, Informative)
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 [zeppelin-nt.com], which has built several large rigid airships in the last few years. But even with carbon fibre and Kevlar, the load capacity is small.
It will never work (Score:3, Interesting)
2. It will be SLOW!!!
3. It will be huge and very dangerous in high winds. Super light and strong composits or not there are limits and this thing would be at the ragged edge.
4. For what? It will be super slow and trains, barges, and ships are very good at moving heavy loads over long distances at slow speeds.
5. No one will fund it. Not only would you have to build this thing but you would have to setup air fields for it. It will not mesh well at the current airports.
One of those great PopSci pipedreams like flying cars.
Seaglider (Score:4, Informative)
Or follow this google search [google.com] 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.
... Air submarine? (Score:4, Funny)
Just call it an airship and be done with it.
Important issue (Score:3, Informative)
The problem is with the physics textbooks (Score:3, Funny)
Perhaps first year physics texts should come with a shrink wrap EULA that states something along the lines of: "The scenarios presented in this book do not accurately represent reality."
Helium isn't renewable (Score:4, Interesting)
Drag, Weight , Size (Score:3, Insightful)
Slow (Score:3, Interesting)
In which case you'd be competing against trains, ships and airships.
Doesn't really matter tho. They're looking for stupid investors- take the money, make an "honest attempt", and walk away.
--
Heck a wind powered blimp would sound even more convincing - just hang an adjustable sail/keel/rotorsail (like gyrocopter) a few hundred feet down, and you could do some sailing, this assumes of course that the winds a few hundred feet down are different enough from the winds above.
Add a windmill or two to get power for miscellaneous stuff for the blimp - assuming different winds at windmill altitude from blimp altitude. Still solar power could be more effective.
Re:MOD PARENT +1 INTERESTING (Score:4, Funny)
Oh, the backup engine is there alright. We just neglected to carry fuel for it onboard :D
Re:MOD PARENT +1 INTERESTING (Score:5, Funny)
In the even of a water landing your seat cushions may be used as a floatation device.
Re:MOD PARENT +1 INTERESTING (Score:3, Interesting)
3 more engines.
This plane (if possable) would have a very high glide ratio, so even if it crashes, unless it's a catastrophic failure, it could be a very soft crash landing.
To me this sounds like some intresting scifi, from a wild imagination, but not very well thought out. I'm shure that there will be something like this eventually, but most likeley not too soon.
The vehicle is really just a durigable with wings, I think that lighter than air flight has a potential to be come a really big thing in the ne
Re:In this house we obey the laws of thermodynamic (Score:3, Insightful)
They don't plan on pumping the helium in and out. It looks like they plan on leaving the helium static in the tanks, and pumping air in and out of other tanks, making the plane weigh more and less. However, it's not really the weight of the plane that matters, it's the density. The goal is to get the average density of all the materials onboard i.e. the people,
Re:Perpetual Motion (Score:4, Insightful)
I think it can work if they can solve the "magical box that can hold a total vacuum that weighs less than the air its going to displace" part of the problem but thats been know about since the days of Boyl and Dalton.
This system uses the energy of the wather system to move around a device that wants to float at a n altitude above ground level. In that way its much like a sail boat. The reality is if anyone can build a large vacuum chamber, they can stick engines on it and get from LA to London much quicker than current jets if they can get up high enough. I figure this will happen about the time someone finds the right stuff to make a space elevator out of.
Re:UGH (Score:3, Interesting)