Author Topic: Air-gravity powered aircraft? (Read 862 times)

texasmom · « **Reply #15 on:** January 02, 2008, 07:49:08 PM »

helium/solar

sounds like kiddie b-day parties & calculators. Won't ever catch me in a plane powered by that.

eskimo2 · « **Reply #16 on:** January 02, 2008, 08:05:51 PM »

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.

AquaShrimp · « **Reply #17 on:** January 02, 2008, 10:20:10 PM »

Just run conventional airliners on biofuel or renewable hydrogen. 100 times more efficient, faster, and safer.

BaDkaRmA158Th · « **Reply #18 on:** January 02, 2008, 10:43:22 PM »

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.

Tac · « **Reply #19 on:** January 02, 2008, 11:09:22 PM »

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.

zmeg · « **Reply #20 on:** January 02, 2008, 11:50:31 PM »

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.

Viking · « **Reply #21 on:** January 02, 2008, 11:54:54 PM »

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.

Holden McGroin · « **Reply #22 on:** January 03, 2008, 12:00:08 AM »

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.

zmeg · « **Reply #23 on:** January 03, 2008, 12:21:50 AM »

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.

Holden McGroin · « **Reply #24 on:** January 03, 2008, 12:34:54 AM »

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.

Coshy · « **Reply #25 on:** January 03, 2008, 05:53:21 AM »

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.