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Engineering a vacuum zepelin?

It's not SF, it's just not any better (and significantly harder) than using a simple helium balloon.
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it has a slight advantage, if it were possible, in that there is no expansion as the vacuum "bottle" rises into an atmosphere unlike a balloon where the gradient shifts as the outer atmosphere thins - but basically dumb idea. The difference in weight of the gas versus vacuum is so miniscule compared to the structural problem.
 
I suppose the situation is even worse in the case of a torus of toruses; i.e., a large ring of small toruses, slightly tapered to fit side by side, completeing a ring of toruses; with interior space evacuated. I suspect the sphere of spheres is better, but as Zig points out, not good enough.

If scaling offers no advantage (possibly disadvantage) then I remain stumped.
But it's been fun, and I thank you all for playing.
 
Wait!

One last thought on the matter from me...and I must confess to being a bit 'pickled' at the moment:

Looking at this issue from the top-side; i.e., assembling a geo-desic framework from orbit, and giving it a wraper of membrane...

And then 'nudging' it out of orbit...

Could it be a practical device from that side?
Would it stabilize at a certain altitude; one that could handle the pressure on the outside?

Or, is it the exact same problem we encounter, attempting to get lift-off from the surface of the planet?

I shouldn't ask this question. In the morning, more brain cells will function, and I will likely see the folly of my query.

But for now, I am curiously stupid.

(Hopefully, my question is understandable.)

If so, might this be the zone of the practical use of the elusive structure?

(Don't go easy on me; I can handle it. Even as I ask, I sense that I'm missing the obvious here.)
 
quarky said:
(Don't go easy on me; I can handle it. Even as I ask, I sense that I'm missing the obvious here.)
Click to expand...

OK, you asked for it....

Altitude doesn't help. The pressure is lower, but so is the boyant force. Your structure can be only a fraction of the strength, but it must also be that fraction of the weight. Your required strength to weight ratio doesn't change.
 
Can you fill a reflective ballon with enough photons to produce 1 atmosphere of internal pressure? What is the energy or mass of those photons?
 
I know that materials sufficient to make an evacuated sphere with a shell light enough to self-lift don't exist yet.

But can anyone give me an estimate of how far off existing materials are? By what factors do, say, steel, titanium, glass, and composite carbon fiber fall short of the mark?

Respectfully,
Myriad
 
macdoc said:
it has a slight advantage, if it were possible, in that there is no expansion as the vacuum "bottle" rises into an atmosphere unlike a balloon where the gradient shifts as the outer atmosphere thins - but basically dumb idea. The difference in weight of the gas versus vacuum is so miniscule compared to the structural problem.
Click to expand...
There'd also be the problem of descent, unless you can release some of the LTA material.

no one in particular said:
Of course it will. A thing filled with helium will float. And nothing is lighter than helium.
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Not by much; at RTP a cubic metre of air masses ~1.2kg, a cubic metre of helium 0.17kg (and hydrogen half that), so a vacuum would only be ~14% lighter.
The materials I've linked to mass around 0.9kg/m3.
 
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SPIN the bastard!
Centrifugal force balances the inward pressure.

Attach gondola to a frictionless bearing on the bottom.
Attach a skyhook to a similar bearing on the top.

Problem solved.
 
Skyhooks have solved many a problem over the years. Most architecture students have relied on them heavily at some stage.......

If you have a skyhook, why do you need to be lighter than air?

Mike
 
Soapy Sam said:
SPIN the bastard!
Centrifugal force balances the inward pressure.

Attach gondola to a frictionless bearing on the bottom.
Attach a skyhook to a similar bearing on the top.

Problem solved.
Click to expand...

Can we eliminate the skyhook?

Inside the vacuum vessile you have a rotating structure that provides the radial force to counter the outside air pressure. The outer skin can be held away frictionlessly by magnetic levitation. You still need vertical support to keep everything from pancaking.

For a tall cylindrical object of radius r and length l, the vertical component of the air pressure is proportional to r2. To resist this force, the cross section of the support structure will also need to have a cross section proportional to r2 and needs a length l. Therefore the mass of the vertical support will scale with displaced volume giving no advantage for large or small scaling.

The rotation could eliminate a large fraction of the necessary structural support so the dynamic structure may be possible where the static structure is not due to material constraints.

ETA: there may be a solution for an infinitely tall stepped cylinder that is wider at the top than at the bottom. The air pressure under each step is sufficient to support that step and the rotation counters the pressure from the sides. There is no top to be supported and therefore no vertical support structure.
 
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Cool.

In early efforts to float a permanent magnet, gyroscopic effect was essential to prevent flipping. In the case of the vacuum balloon, wouldn't there need to be some atmosphere contained, to get any advantage from rotation?
 
Dan O. said:
Can you fill a reflective ballon with enough photons to produce 1 atmosphere of internal pressure? What is the energy or mass of those photons?
Click to expand...

Radiation pressure from the Sun at 1AU is 9.15 microPascals. Atmospheric pressure is 101325 Pa. To be viable, you would need a light source roughly 10 orders of magnitude brighter than the Sun.
 
Evilgiraffe said:
Radiation pressure from the Sun at 1AU is 9.15 microPascals. Atmospheric pressure is 101325 Pa. To be viable, you would need a light source roughly 10 orders of magnitude brighter than the Sun.
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I'm thinking Project Orion...
 
Well, if you exploded a nuclear weapon inside an evacuated vessel there would probably be a period of time where the radiation pressure would equal the atmospheric pressure, and the entire assembly would start to float. However, that period might be quite brief. I don't think it'll catch on as a method of transport....
 
Evilgiraffe said:
Dan O. said:
Can you fill a reflective ballon with enough photons to produce 1 atmosphere of internal pressure? What is the energy or mass of those photons?
Click to expand...

Radiation pressure from the Sun at 1AU is 9.15 microPascals. Atmospheric pressure is 101325 Pa. To be viable, you would need a light source roughly 10 orders of magnitude brighter than the Sun.
Click to expand...


It's going to be a bit on the bright side so I would suggest wearing shades :)

The question is: how much weight does this amount to?


Solar energy flux density at 1AU: 1370 W/m2
Radiation pressure from the Sun at 1AU: 9.15 microPascals
Atmospheric pressure: 101325 Pa

Required solar energy density to achieve 1 atmosphere pressure:
1370 W/m2 * (1.01e5 Pa /9.15e-3 Pa) = 1.52 × 1010 W/m2
multiplied by the surface area of a sphere multiplied by the travel time for light to bounce from one side of a sphere to the other and divided by the speed of light squared to get the mass of the trapped energy per cubic meter of the enclosed sphere ...

1.77× 10-15 kg / m3

Now that is what I call light weight.
 
It's a goer. Just as soon as we can find a perfectly reflective material that can withstand 15.2 jiggaWatts* per metre squared. Somebody get Emmett Brown on the phone!

*Apologies, Back to the Future was on TV this afternoon.
 
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