Floating space?

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Floating space?

Postby Ideas sleep furiously. » Mon Nov 08, 2010 10:55 am UTC

Now, let me start by saying that I'm an idiot. And any ideas that I have are quite possibly on the same level as 'aliens on the moon'.

Anyhow, I had an idea, about a device that could contain nothing, space if you will, that is strong enough to not collapse in on itself under pressure.
Would this theoretical device float in air? (Assuming it was air-tight and that the device's mass was less then the buoyancy it created).

Edit: And, assuming it's possible, what could it's uses be?

Flying cars anyone?
Last edited by Ideas sleep furiously. on Mon Nov 08, 2010 2:03 pm UTC, edited 3 times in total.

tckthomas
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Re: Floating space?

Postby tckthomas » Mon Nov 08, 2010 1:12 pm UTC

I once thought about this, I am also interested in the answer...

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Re: Floating space?

Postby RonWessels » Mon Nov 08, 2010 1:22 pm UTC

That depends on the overall density (mass divided by volume) of your device. Just like something that is less dense than water will float in water, something that is less dense than air will float in air. This is why helium balloons float: the helium is lighter than air so it plus the weight of the balloon itself weigh less than the equal volume of (ground level) air.

Of course, complicating the issue is the fact that air density decreases as altitude increases, so your hypothetical device will rise until equilibrium is reached.

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Stacy S.
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Re: Floating space?

Postby Stacy S. » Mon Nov 08, 2010 1:44 pm UTC

Would a balloon filled with vacuum instead of helium float?
http://science.howstuffworks.com/scienc ... ion194.htm

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Re: Floating space?

Postby Izawwlgood » Mon Nov 08, 2010 1:50 pm UTC

Heh, a forcefield that lets air out but doesn't let air in, would float away. That's vaguely poetic.
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Re: Floating space?

Postby Tass » Mon Nov 08, 2010 2:05 pm UTC

We had a discussion a while ago whether it would actually be practically possible to make a vacuum balloon like this.

Theoretically - of course.

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Re: Floating space?

Postby Ideas sleep furiously. » Mon Nov 08, 2010 2:11 pm UTC

Yeah, I searched and found nothing, figures i would miss it.

Anyhow, I think the most structurally sound shape for holding a vaccum would be a sphere for even distribution of pressure.
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Re: Floating space?

Postby Korrente » Mon Nov 08, 2010 2:49 pm UTC

This was actually tried a very long time ago, around the time of the first hot air balloon flight. I'm not sure how far he got, but a monk tried to evacuate large copper spheres and attach them to a gondola. Obviously the copper was too dense, but at least he was thinking outside the box.

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Re: Floating space?

Postby Ideas sleep furiously. » Mon Nov 08, 2010 3:01 pm UTC

I think the 'easiest' way to do it would be to go into space and 'trap' the space there, I don't think a vaccum would be very easy to replicate on earth.
Or is it?
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Re: Floating space?

Postby Technical Ben » Mon Nov 08, 2010 3:03 pm UTC

Or outside the spherical copper chamber? :wink:
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Re: Floating space?

Postby kjsharke » Mon Nov 08, 2010 4:09 pm UTC

Ideas sleep furiously. wrote:I think the 'easiest' way to do it would be to go into space and 'trap' the space there, I don't think a vaccum would be very easy to replicate on earth.
Or is it?


Sure, everyone loves to work with vacuums! (a lot of 'hurry up and wait' in my limited experience, but I still liked it)

The problem: how much does a cubic meter of air weigh? Wikipedia says 1.2 kg, so by evacuating the air in that space, you lose 1.2kg. But to maintain that much negative pressure, you need a stiff structure. A cubic meter is pretty huge, and anything that can maintain a vacuum for that large a volume will likely weigh a lot more than 1.2 kg, so the total density is a great deal more than air, and it won't float.

If you instead replace the air with a lighter gas (helium/hydrogen/hot air), then your vessel can be equal pressure or positive pressure, so you don't need a lot of structure to contain it. You only save a fraction of that 1.2kg/m^3, but your container can be so much lighter, it is much easier to make it float.

Thoughts for building a vacuum-balloon: You could make an octohedron with three sticks (along x,y,z axes) and some wire (between the endpoints of the sticks), and cover it with an inelastic film (mylar?). Hey, they made a lead balloon..

edit: kinda ninja-ed by the howstuffworks link...

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Re: Floating space?

Postby Zamfir » Mon Nov 08, 2010 4:29 pm UTC

kjsharke wrote:
Ideas sleep furiously. wrote:I think the 'easiest' way to do it would be to go into space and 'trap' the space there, I don't think a vaccum would be very easy to replicate on earth.
Or is it?

You only save a fraction of that 1.2kg/m^3

Hydrogen has a density of about 0.1, Helium 0.2, giving you a buoyancy of at least 1.0 kg/m^3. Going to vacuum is clearly not worth the trouble.

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Re: Floating space?

Postby gmalivuk » Mon Nov 08, 2010 4:47 pm UTC

Ideas sleep furiously. wrote:Yeah, I searched and found nothing, figures i would miss it.
That's understandable, since the original thread was asking about vacuum zeppelins, rather than balloons (and just searching for "vacuum" probably gives too many results to be useful).

But in any case, since that thread does already exist, further discussion should take place over there.
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