Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Viking on January 02, 2008, 03:27:54 AM
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http://www.youtube.com/watch?v=tPbu5UeW4uk&feature=related
Interesting concept, but would it be practical?
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The plane would have to be built very lightly in order for helium to provide most of the lift.
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Let's see:
1. Compressed air exists in the plane before it takes off the first time.
2. Helium (which was produced somehow) exists in the a/c before liftoff.
3. The a/c rises on the buoyancy of helium, and compressed air is used to power thrust turbines.
4. When max buoyancy altitude is reached, compressed air is let into the gas bag area to contract the gas bags.
5. Wings (which i guess have yet to be used) are swept back and the a/c glides.
6. During the gliding phase, fans on the outside power air compressors to recharge the compressed air.
7. Once the minimum altitude is reached, the cycle begins anew.
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A few questions:
A. In order for me to get from a to b, I must use energy, and for this a/c to get from a to b it must use energy. Yet they say the a/c uses no fuel. Are they saying the production of helium and the production of compressed air are somehow outside their energy balance?
B. why are the wings variable sweep if they are not used except for one flight regimen?
C. In the old dirigible days, ground handling, especially putting the airships in the hanger was extremely difficult. How are you s’posed to handle a hybrid dirigible in the wind?
I am a big fan of dirigibles, and would like to see a helium Hindenburg cruise line. You could see the wildebeest drive across the Serengeti or watch the Porcupine herd travel across the arctic plain while seated in the observation deck.
But I think this machine as explained is a pipe dream which violates the second law. There is always a fuel cost unless you are just blowing in the wind, and even then you must pay for the helium.
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A: Yes. The helium is part of the plane; it is not released. The compressed air is resupplied for every cycle of flight. In the video they say the plane uses compressed air driven turbines to produce forward thrust, but in reality they don't actually need to. When the aircraft is positively buoyant it can glide forward using the force of the buoyancy just like it uses gravity on the downward leg. The compressed air is used to compress the helium balloons and make the aircraft negatively buoyant. It should work ... I think.
B & C: No idea.
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If designed right the energy needed could come from solar.
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sounds like a slow 163 minus the guns and roket moter
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Originally posted by Ghosth
If designed right the energy needed could come from solar.
That would add more weight unless they could come up with a lightweight film solar panel. I don't think they need it, as they claim energy is produced by the turbines.
Holden McGroin
2. Helium (which was produced somehow) exists in the a/c before liftoff.
I don't think the helium is used as a fuel but rather as a buoyancy method. I don't think it's released during flight so it doesn't have to be refilled.
If it will work or not I have no clue as I'm not an engineer, but I do agree it would like have issues in high wind or storm conditions. Still it's kinda cool though.
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The plane is supposed to have a constant amount of helium which is initially compressed with compressed air. When the ac takes off the compressed air is released which will move the ac and lift it off. When the compressed air reservoir depletes it releases helium which replaces eventually enough air to make the ac buoyant. Using this buoyancy the ac uses it's wings to glide upwards. Once max altitude is reached and plane starts to slow down, it's turned into a dive by compressing a part of the helium again (using a smaller reservoir of compressed air remaining). During the glide propellers are activated which will compress necessary air to repeat the cycle.
Helium = steady, compression and thrust generated from gravity.
Of course it will have a very hard time in stormy weathers and/or with supermorbidly obese passengers. :D
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Sounds too heavy to me for the lifting volume. Look at the volume of gas required to lift a blimp with a simple gondola.
Charon
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Interesting concept.
Now all they need to do is transform the concept into a 4-man vehicle and make us the first flying car, fuel-free. Woot!
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http://www.jpaerospace.com
IMO the puncture problem will be the biggest obstacle to this sort of vehicle.
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ewps didnt see that link moot put in there. nm
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Great idea; I bet they will get Miss Teen South Carolina to fly it...
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Originally posted by Charon
Sounds too heavy to me for the lifting volume. Look at the volume of gas required to lift a blimp with a simple gondola.
Charon
And this is where my question comes in. For helium to have any buoyancy, it must be in full expanded mode, i.e. no compression. A tank of compressed helium has no buoyancy.
The volume needed to be able to lift off an aircraft like that would be a lot more than they think it is.
Unless I'm completely wrong.
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The question is can the plane compress enough air in it's descent to compress the helium sufficiently. Shouldn't be too dificult to simulate that.
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helium/solar
sounds like kiddie b-day parties & calculators. Won't ever catch me in a plane powered by that.
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Their problem is that these guys have little understanding of strength or efficiency.
For this thing to lift off it would have to be built very light which would make its strength borderline. Airships have trouble dealing with rough weather; this thing is two airships attached together and has some giant wings to boot; it should be even more fragile than any airship ever built. Its payload would also be lessened by the mass of the wings. Whatever the heck kind of tanks are going to hold all of this compressed air are certainly going to have some mass and there would have to be a lot of them. Then there are the compressors and/or turbines; that’s just got to work out to be a heavy power source due to its size and inefficiency (if they want any range).
Compressing the helium would also be an issue, especially at altitude: do you use the main bags and just compress them? If so they had better be super duper strong and what the heck is going to squish them? Try squeezing a helium balloon just a bit; that’s going to take a lot of force. Or, do you compress the helium and pump it into tanks? Great, more tanks just like the compressed air tanks. Once again it would need many of them; they would have to be strong, which is already going to bump the weight up even more. This thing already is too heavy and too weak.
Now let’s just suppose that this thing has risen to altitude, the stored compressed air has compressed the helium so that it’s significantly heavier than air and it’s doing the glider thing. It certainly would be possible to have a turbine or prop running a compressor that’s compressing air; the efficiency would be awful however. Either the thing has giant turbines or props that cause a huge amount of drag and kill the glide ratio, or they are small and produce little compressed air. It probably would be better to go with the latter because the system would be terribly inefficient anyway.
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Just run conventional airliners on biofuel or renewable hydrogen. 100 times more efficient, faster, and safer.
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If it can make itself lighter than air and never crash, awesome.
Ten miles? thats enough to use it to launch thing into space.
Take this platform and super size it, nasa's out of a job.
Terrorest cant use it to bomb, it uses no fule and makes no sound.
Wow, just wow.
And with the recent advancements in battery fuel cells, im sure they can add backup systems just in case anything did happen "power wise"
May not be a mach 3 bird, but at ten miles above the planet you can still cover a huge amount of land, and with crew quarters it could stay in the air...forever.
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well eskimo...
im not saying itd be easy or cheap but hey.. titanium is pretty darn strong and light and so are some of those new high tech material composites that have come out in the past decade.
I dont doubt they can build one strong enough.. i do doubt the thing's safety in a windy situation.
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The weight of the air and helium onboard the ship would be exactly the same reguardles of weather or not it's compressed, it won't fly.
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The weight is irrelevant. It is how much air it displaces that is important. Put a kilogram of helium into a small light container at high pressure and it will fall. Put one kilogram of helium into a balloon and it will fly.
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But the density and weight does change. When the helium is allowed to expand, the air that was displacing the helium envelope is tossed overboard, lightening the ship.
To compress the helium envelope, air from outside the ship is pumped in displacing and compressing the helium.
It kind of an intriging concept, but energy used to compress the air needs to come from outside the a/c system. Energy is not free. You can't get it all from the momentum of the decending ship.
The buoyancy system used here is similar to ballast tanks on a submarine.
Much energy is used to compress the air used to blow out seawater filled tanks.
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The weight of the compressed air needed to drive the pump to bring in outside air would be the same as the air it pumps in minis an effenciency
factor, it won't fly.
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That's right...
"Some of the stored compressed air is then expanded into the dirigible areas, decreasing the buoyancy effect of the helium and starting the aircraft's descent phase. " from the article I read is an incorrect thought. Total weight and total volume would be unchanged.
They would have to bring air from the atmosphere into the ship in order to compress the helium go down. Compressed air could not be the source for power for thes compressors. That would just be a loss leader.
But they could have the buoyancy to rise.
Trivia for today: The Hindenberg and other dirigibles used to rub up against clouds to get some water ballast to compensate for fuel burn.
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So, what happens if you put it on a conveyor belt moving at exactly the same speed as the wheels?
It looked like, to me at least, not so much as a "Hey lets do this" but rather a "What if/would this work" kind of thing.
Interesting, impractical, but I'm sure someone said that about the automobile.