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I have been told that if you could create a perfect vacuum you could achieve lift much like a helium filled balloon. Assuming this is correct or at least partly do you have to have a perfect vacuum?
Sure, a vacuum is even lighter than helium gas. There's no reason it
would have to be a perfect vacuum, or even a very good one. The last 1%
of the gas molecules only have 1% of the total weight. The reason that
vacuum balloons aren't used is that the outside pressure would make
them collapse unless they have very sturdy walls. Sturdy walls are not
practical for something you want to have be lighter than air.
(republished on 07/31/06)
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