Vacuum Zeppelin

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Vacuum Zeppelin

Postby Master Gunner » Mon Oct 15, 2007 11:29 pm UTC

Okay, I'm going to guess that this is either completely inane or discussed before, either way, I apologize.
So, earlier today I was thinking about Zeppelins (not uncommon for me) and how they are built. Now, my understanding is that in a Zeppelin, we fill the insides of the massive "balloon" with a lighter-than-air gas (such as Helium or Hydrogen) in order to reduce the average density of the whole Zeppelin to less than that of air. This is what causes it to rise and become buoyant. So this brings me to my question: would it be (theoretically) possible to, instead of filling it with helium or hydrogen, completely empty it and turn the insides into a vacuum to lower the average density? Could this actually work to allow a zeppelin to fly?

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Re: Vacuum Zeppelin

Postby Geekthras » Mon Oct 15, 2007 11:37 pm UTC

I've wondered about this myself and done the following thought experiment:

Imagine a 5 cm radius sphere, not hollow, of a light metal that has a density of say 2 g/cm^3. This would sink in water. Now hollow out the center until you have an empty 4 cm radius sphere
v=4/3*125 or about 170 cm^3 and mass=(4/3*125-4/3*64)*2 or (170-90)*2 or 160 grams.
160/170 < 1/1 so it would float. Now do that with a big thing, with lighter materials and a thinner crust.


The math is just to back it up.
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Re: Vacuum Zeppelin

Postby hyperion » Mon Oct 15, 2007 11:46 pm UTC

I've thought about this, and I came to the conclusion that anything strong enough to support a vacuum would be too heavy to fly.
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Re: Vacuum Zeppelin

Postby Solt » Tue Oct 16, 2007 12:02 am UTC

Yes it would technically work but it is unfeasible.

With hydrogen or helium sacks, you can still maintain a relatively high pressure inside the vessel- if not at, then close to atmospheric pressure. This means the membranes do not have to be very strong at all to contain the gas- net pressure 0 Pascals. If you have heaters you can carry even less and be even lighter- just heat the smaller quantity of gas until it expands and develops 1 atm internal pressure. This is assuming rigid membranes. If you had a flexible membranes, this wouldn't even be a problem because the pressures would automatically equalize as the membrane deforms. Of course, a flexible membrane containing a vacuum would be 'crushed' into nothingness so you need a rigid shell to actually contain the vacuum.

If you had a vacuum inside, it would be like putting a pressure of 1 atm or 100 kPa on the membrane (since atmospheric pressure is not balanced from the inside). For 1 m^2 of surface area, that's 100,000 Newtons or 10,000 Kilograms of force. This is like piling 7 cars (compacts) on an area the size of an average work desk. Would it stand up? Fuck no, it would be crushed by just 1 car. You'd need some serious steel supports running through the vacuumed space and a skin of steel a half-inch or more thick. Long story short, the weight of the materials needed to maintain a vacuum space under 1 atm external pressure without imploding would likely far exceed the buoyant force you would create and it would not rise.

Modern composites might give you better numbers. I'd have to do some calculations to see if a carbon fiber shell could contain a vacuum under these conditions and still float. I'm still guessing no, though.
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Re: Vacuum Zeppelin

Postby Avram » Tue Oct 16, 2007 12:23 am UTC

I propose we experiment with this concept on a smaller scale:

1 - obtain party balloon
2 - suck air out of said balloon to create vacuum
3 - release balloon
4 - check for signs of floating

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Re: Vacuum Zeppelin

Postby Master Gunner » Tue Oct 16, 2007 12:23 am UTC

I figured that any material that could withstand a vacuum would be too heavy, but I just wanted to see if it would be possible using unobtainium, and I guess it is from what you've said.

Edit: Fonkey, that wouldn't work as the balloon would instantly collapse in on itself, you need supports to keep it expanded and thus lower the density, but maybe some thin metal wire would work on that scale, but it's doubtful.

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Re: Vacuum Zeppelin

Postby Solt » Tue Oct 16, 2007 1:02 am UTC

Yes, if you had unobtainium it would be possible.

Fonkey wrote:I propose we experiment with this concept on a smaller scale:

1 - obtain party balloon
2 - suck air out of said balloon to create vacuum
3 - release balloon
4 - check for signs of floating


An un-inflated balloon is the same thing as a balloon that contains a vacuum :P
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Re: Vacuum Zeppelin

Postby Gelsamel » Tue Oct 16, 2007 5:06 am UTC

Even if it could survive the force of the atmosphere it would probably float too high.
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Re: Vacuum Zeppelin

Postby po2141 » Tue Oct 16, 2007 8:00 am UTC

For a container to be strong enough to enclose a vacuum in a 1atm environment, it needs the same strength as if it were to survive being submerged in 10m of water with 1atm inside. Submarines do this all the time. Now you just have to make them muchmuchmuchmuchmuch lighter....
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Re: Vacuum Zeppelin

Postby evilbeanfiend » Tue Oct 16, 2007 8:16 am UTC

Gelsamel wrote:Even if it could survive the force of the atmosphere it would probably float too high.


that's what ballast is for. but yes floating with a vacuum while possible would require a very strong very light material to hold the vacuum it's certainly not possible with current materials.
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Re: Vacuum Zeppelin

Postby Solt » Tue Oct 16, 2007 9:51 am UTC

po2141 wrote:For a container to be strong enough to enclose a vacuum in a 1atm environment, it needs the same strength as if it were to survive being submerged in 10m of water with 1atm inside. Submarines do this all the time. Now you just have to make them muchmuchmuchmuchmuch lighter....



Except water provides about 1000 times the buoyant force of air. Bearing the forces isn't a problem, bearing them and being light is. Specifically, you'd have to be 1,000 times lighter than a submarine but with the same structural strength. Well, less since subs dive much deeper than 10m.
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Re: Vacuum Zeppelin

Postby evilbeanfiend » Tue Oct 16, 2007 10:00 am UTC

incidentally a vacuum balloon would presumably be much more dangerous than a helium balloon in the event of a puncture.
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Re: Vacuum Zeppelin

Postby po2141 » Tue Oct 16, 2007 12:56 pm UTC

They have "vacuum dirigibles" in the Iain M Banks books. They use a rigid balloon but instead of the balloon being evacuated they fill it with lot and lots of small, light, thin walled evacuated spheres. That way they can shift the balls en-masse and "pump vacuum" from place to place. Apparently, in his universe, it provides only marginally more lift than other gases but they do it cos its cool.
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Re: Vacuum Zeppelin

Postby Cosmologicon » Tue Oct 16, 2007 2:35 pm UTC

If you charged the hull, could you use electrostatic repulsion to keep it inflated?

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Re: Vacuum Zeppelin

Postby MotorToad » Tue Oct 16, 2007 3:18 pm UTC

I like the idea of the carbon fiber vacuum sphere. I'm sure it wouldn't be too difficult to construct it to be lighter than the air it displaces and more than strong enough to cope with the pressure. Cost, however, is another can of bean counters. :)

The math is simple, though. The weight of the object just needs to be slightly less than the weight of its volume in air.(I know that's superobvious, but no one has clearly spelled out buoyancy here.)

The best part of the idea of the vacuum balloon, though, is how easy buoyancy can be controlled with a bladder at its center of mass and a vacuum pump to evacuate it. Vent air in to go down, suck it out to go up. It may not be crash-proof, but at least you won't float off into near-space. :)


Edit: the more I think about this, the more I like it. I've been bothered recently by the fuel consumption of commercial air traffic, and the (seemingly) universally ignored fact that they deposit CO2 in the part of the atmosphere that lacks trees.

For one thing, compare the cost of this to the cost of, say, a 747-400. I don't think the difference would be all that great.

Compare fuel consumption of this on a transatlantic flight to a 747 at Mach 0.9. Sure, it'd take 3-4 days, but imagine all the mile-high fun you could have. People lock themselves on boats for weeks at a time, wtf not a balloon. And you can't bungee jump off of a boat.
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Re: Vacuum Zeppelin

Postby evilbeanfiend » Tue Oct 16, 2007 3:21 pm UTC

Cosmologicon wrote:If you charged the hull, could you use electrostatic repulsion to keep it inflated?


i guess - sounds rather like running an energy saving bulb off a jet engine though
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Re: Vacuum Zeppelin

Postby Gelsamel » Tue Oct 16, 2007 6:14 pm UTC

Spheres are spatially inefficient (though structurally strong). Also vacuums aren't exactly cheap to produce. The matinence would be ridiculous. And there would be air/other gasses in between the spherical gaps. And you have to have spheres if you want to pump them places.
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Re: Vacuum Zeppelin

Postby Master Gunner » Tue Oct 16, 2007 8:31 pm UTC

While it would be completely unfeasible, a vacuum zeppelin would get around both the problems of helium shortages and hydrogen going boom. As for the internal structure, I'm thinking it would be a small number of fixed spherical "vacuum bladders" on the inside, and you wouldn't have to pump the vacuum around, but rather use normal air as ballast and pump that around to keep it balanced.
Now I'm wondering, since a vacuum would be impossible/impractical, how low an internal pressure could we achieve with modern materials and still have a reasonable mass?

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Re: Vacuum Zeppelin

Postby LoopQuantumGravity » Wed Oct 17, 2007 2:17 am UTC

Cosmologicon wrote:If you charged the hull, could you use electrostatic repulsion to keep it inflated?


I wasn't going to comment on this thread, but this is quite possibly the worst idea I have ever heard.
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Re: Vacuum Zeppelin

Postby Hexadecimator » Wed Oct 17, 2007 2:55 am UTC

I have mass of 77kg, to lift myself, I would need to displace around 64m3 of air with vacuum or around 70m3 of air with helium. Sorry to burst your bubble (*cough*badpun*cough*), but it doesn't help that much.
However, the moment I get a hold of some unobtanium, this is exactly what I am building. Unless unobtanium turns out to also be a superconductor at room temperature, in which case I would do slightly cooler things. Hmmm... superconducting zeppelins = awesome?
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Re: Vacuum Zeppelin

Postby Cosmologicon » Wed Oct 17, 2007 3:31 am UTC

LoopQuantumGravity wrote:
Cosmologicon wrote:If you charged the hull, could you use electrostatic repulsion to keep it inflated?


I wasn't going to comment on this thread, but this is quite possibly the worst idea I have ever heard.

Aw come on, I've got much worse ideas than that. Seriously, is there no way it could be made to work? Obviously you'd have to shield it within an equal and opposite charge, but I think that's the only major hurdle. It sounds ridiculously infeasible, but not fundamentally impossible, no? Is there something else I'm overlooking?

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Re: Vacuum Zeppelin

Postby LoopQuantumGravity » Wed Oct 17, 2007 4:16 am UTC

Cosmologicon wrote:
LoopQuantumGravity wrote:
Cosmologicon wrote:If you charged the hull, could you use electrostatic repulsion to keep it inflated?


I wasn't going to comment on this thread, but this is quite possibly the worst idea I have ever heard.

Aw come on, I've got much worse ideas than that. Seriously, is there no way it could be made to work? Obviously you'd have to shield it within an equal and opposite charge, but I think that's the only major hurdle. It sounds ridiculously infeasible, but not fundamentally impossible, no? Is there something else I'm overlooking?


Well, everyone on the balloon would die from massive lightning bolts when the air was ionized by the gigantic electrical fields. Also, I'm sure that would mean trouble for the huge generator you'd need to make that kind of potential... Or, hey, maybe you could just beam the power there with Tesla's "wireless power" ideas?

But other than that, it's a fantastic idea.
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Re: Vacuum Zeppelin

Postby Cosmologicon » Wed Oct 17, 2007 2:27 pm UTC

I think you're trying to trick me. I think that you see something I don't, and 10 posts down, after an exacting series of one-step-at-a-time posts, you'll finally say, "What? You didn't know that from the very beginning? What a buffoon!" and let out a hearty guffaw. I'm going to take the bait, but I wish you'd just cut to the chase.

Can't you just cancel out the external electric field with an equal and opposite charge around the outside? If not, why not, and if so, what's then the problem?

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Re: Vacuum Zeppelin

Postby LoopQuantumGravity » Thu Oct 18, 2007 12:40 am UTC

Cosmologicon wrote:I think you're trying to trick me. I think that you see something I don't, and 10 posts down, after an exacting series of one-step-at-a-time posts, you'll finally say, "What? You didn't know that from the very beginning? What a buffoon!" and let out a hearty guffaw. I'm going to take the bait, but I wish you'd just cut to the chase.

Can't you just cancel out the external electric field with an equal and opposite charge around the outside? If not, why not, and if so, what's then the problem?


With conductors, that's only going to work if you surround the charged area by a grounded conductor. Another charged one won't work. See: http://falstad.com/emstatic/ if you don't believe me! (Draw a circle out of + conductors and put it inside one of - conductors).

With non-conductors, it's only going to be zero field over large distances. Right next to it, there will still be a large field. Also, you'd have to make the blimp out of something non-conductive, which would be a problem. There would be larger technical problems in trying to do this, too.

And the blimp would have a nonzero magnetic moment, too!

Either way, it won't work, due to the crazy high fields you'd need to have to do this.
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Re: Vacuum Zeppelin

Postby Minerva » Thu Oct 18, 2007 12:38 pm UTC

po2141 wrote:They have "vacuum dirigibles" in the Iain M Banks books.


The other fictional reference that first came to my mind is of course Neal Stephenson's The Diamond Age.

As we've already largely discussed in the thread, it's all about having strong enough, light enough materials.

Nanomaterials could, in theory, do it.
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Re: Vacuum Zeppelin

Postby Cosmologicon » Thu Oct 18, 2007 6:12 pm UTC

LoopQuantumGravity wrote:
Cosmologicon wrote:Can't you just cancel out the external electric field with an equal and opposite charge around the outside? If not, why not, and if so, what's then the problem?


With conductors, that's only going to work if you surround the charged area by a grounded conductor. Another charged one won't work. See: http://falstad.com/emstatic/ if you don't believe me! (Draw a circle out of + conductors and put it inside one of - conductors).

With non-conductors, it's only going to be zero field over large distances. Right next to it, there will still be a large field.

By Gauss's Law, if you have a spherical shell within a larger spherical shell of equal and opposite charge, there will be zero E-field outside them, even close to the surface. It doesn't work with circles like it does with spheres. Is there some reason Gauss's Law doesn't apply here?

I believe you that the field within would make it infeasible. I get that it would require a field of about 50 MV/m. High voltage power-lines have a field strength of what? 100 kV/m?

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Re: Vacuum Zeppelin

Postby McHell » Thu Oct 18, 2007 8:21 pm UTC

Gelsamel wrote:Spheres are spatially inefficient (though structurally strong).

What? Care to name one more efficient shape? Or do I misunderstand you.

To save you time, consider the fact that spheres have a minimal surface/volume ratio, and the bigger they get the better the ratio (as it scales linearly with the radius).

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Re: Vacuum Zeppelin

Postby oxoiron » Thu Oct 18, 2007 9:06 pm UTC

From: http://en.wikipedia.org/wiki/Aerogel
The world's lowest-density solid is a silica nanofoam at 1 mg/cm3, which is the evacuated version of the record-aerogel of 1.9 mg/cm3. The density of air is 1.2 mg/cm3.

If it is possible to reintroduce gas into and then reevacuate this substance, then it should be possible to cover a large chunk with foil and hook it up to a vacuum pump to regulate the level of reduced pressure inside the foam. The foil would prevent air from entering the foam and the foam would prevent the foil from collapsing under atmospheric pressure. Hang a gondola off the bottom, and problem solved.

Unfortunately, I suspect that it is not possible to move gas in and out of the foam, or it wouldn't be much of an anti-convective insulator. My guess is that the evacuation takes place during synthesis and is permanent and irreversible.

EDIT: from the same article..."They are good convective inhibitors because air cannot circulate throughout the lattice."

I guess that screws that idea, but it still might be possible to create a nanoporous material that allows air to move through it, is less dense than air when evacuated, and strong enough to not collapse under atmospheric pressure.
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Re: Vacuum Zeppelin

Postby LoopQuantumGravity » Fri Oct 19, 2007 3:10 am UTC

Cosmologicon wrote:
LoopQuantumGravity wrote:
Cosmologicon wrote:Can't you just cancel out the external electric field with an equal and opposite charge around the outside? If not, why not, and if so, what's then the problem?


With conductors, that's only going to work if you surround the charged area by a grounded conductor. Another charged one won't work. See: http://falstad.com/emstatic/ if you don't believe me! (Draw a circle out of + conductors and put it inside one of - conductors).

With non-conductors, it's only going to be zero field over large distances. Right next to it, there will still be a large field.

By Gauss's Law, if you have a spherical shell within a larger spherical shell of equal and opposite charge, there will be zero E-field outside them, even close to the surface. It doesn't work with circles like it does with spheres. Is there some reason Gauss's Law doesn't apply here?

I believe you that the field within would make it infeasible. I get that it would require a field of about 50 MV/m. High voltage power-lines have a field strength of what? 100 kV/m?


If what you have is a perfect sphere, yeah, but I don't think the field would cancel if it were a blimp-shape in general. And the higher voltage the more perfectly spherical you'd need the surface to be. I'm also thinking that you couldn't guarantee that the charge distribution would be uniform anyway, for something that large and moving in a magnetic field, which would give you a field that wasn't zero outside.
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Re: Vacuum Zeppelin

Postby akhmeteli » Fri Oct 19, 2007 8:17 am UTC

You may wish to look at our US patent application 20070001053 (11/517915). We propose an evacuated sandwich spherical shell with two thin face sheets and a light core between them. Finite element analysis confirmed that the structure using commercially available materials (e.g., boron carbide face sheets and aluminum honeycomb core) can be light enough to float in air and strong enough to withstand the atmospheric pressure with decent safety factors for strength, buckling, and intracell buckling. Actual manufacturing, while definitely possible, is not easy.

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Re: Vacuum Zeppelin

Postby hyperion » Fri Oct 19, 2007 8:32 am UTC

McHell wrote:
Gelsamel wrote:Spheres are spatially inefficient (though structurally strong).

What? Care to name one more efficient shape? Or do I misunderstand you.

He means you can't pack them together without massive gaps between them. [I think]
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Re: Vacuum Zeppelin

Postby evilbeanfiend » Fri Oct 19, 2007 8:48 am UTC

as long as there is literally nothing in between them the gaps pose no problem for a vacuum zeppelin, the main problem would be that having multiple compartments increases the weight
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Re: Vacuum Zeppelin

Postby Gelsamel » Fri Oct 19, 2007 9:54 am UTC

HYPERiON wrote:
McHell wrote:
Gelsamel wrote:Spheres are spatially inefficient (though structurally strong).

What? Care to name one more efficient shape? Or do I misunderstand you.

He means you can't pack them together without massive gaps between them. [I think]


Exactly, if the balls were static you could factor in the space in the gaps (which will obviously not be a vacuum) into the density and you still might have enough to float, however when pumping the balls around you'd me moving the spaces around as well, which would affect the weighting and density over the ship as well as the balls affecting it as well. I guess it could be possible to balance it...
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Re: Vacuum Zeppelin

Postby evilbeanfiend » Fri Oct 19, 2007 10:00 am UTC

another point - the shape of any internal compartments is irrelevant as there is equal pressure on both sides - the shape of the outer shell may be important as you have to hold back the atmosphere
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Re: Vacuum Zeppelin

Postby __Kit » Wed Nov 07, 2007 8:31 am UTC

Wait, you mean like a... Lead Zeppelin?
=]

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Re: Vacuum Zeppelin

Postby Geekthras » Sat Nov 10, 2007 5:19 pm UTC

If you got it to work right, it would be like an elevator to heaven.


Or space.
Wait. With a SPOON?!

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Re: Vacuum Zeppelin

Postby yy2bggggs » Sat Nov 10, 2007 6:51 pm UTC

To address a few problems here:
How to create the vacuum
Use an expanding framework.

If there is a leak...
...then, what, there will be an explosion? The insides of the structure simply slowly fill with air. There may very well be dangerous leak scenarios, but certainly not all leaks are catastrophic--they simply reduce the vacuum (ignoring the capabilities of pumps), possibly forcing you to land earlier.

Strength to weight issue
This is the one issue that I think may be significant. But at the very least, you can build the relative vacuum with various starting portions of helium (at the extreme, a trivial "vacuum zeppelin" would simply be a regular helium filled zeppelin, with the frame maintaining a slight bit of the pressure equalization).

Disclaimer: I make no claims as to the feasibility of such zeppelins.
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Re: Vacuum Zeppelin

Postby Zake » Sun Nov 11, 2007 2:36 am UTC

Its a concept which has interested me for awhile since I saw it in Diamond Age; alas, the math says its unlikely.

...At least near sea level. How about we fly our theoretical vacuum zeppelin really high up in the atmosphere- at this point, there is less atmospheric pressure to worry about, and (if my physics intuition serves me here) the benefit of using vacuum rather than hydrogen becomes that much greater. Near-orbital zeppelins would be around as awesome as normal ones, IMHO.

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Re: Vacuum Zeppelin

Postby grythyttan » Sun Nov 11, 2007 6:29 pm UTC

Yep, they would be awesome, but how do we get them up there? If they are built to survive only at those heights they would not survive construction at ground level.

We would have to build them in low orbit or something.
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Re: Vacuum Zeppelin

Postby Master Gunner » Sun Nov 11, 2007 7:25 pm UTC

What's wrong with with building stuff in orbit? I think that would be awesome.
On a more serious note, you could empty the gas chambers through use of a vacuum pump, not the most practical option maybe, but no reason you couldn't use it to lower internal pressure, and when you want to come down, just reverse the process.


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