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Thread: Contained Vacuum Question.

  1. #1
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    Contained Vacuum Question.

    Now that we have graphene...

    What's the main engineering challenge to using evacuated cells as a "lifting gas" for lighter than air vehicles?

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  2. #2
    I think making enough cheaply right now it is about $400-1000 a gram and to build a big enough airship that a lot of graphene,
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  3. #3
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    I think it's a question of the ability of the balloon to maintain its size. If there's hydrogen or helium gas inside, the gas will put pressure on the balloon to expand, which is counterbalanced by the pressure of the atmosphere. But if there's a vacuum inside, the balloon will collapse unless you make it strong enough to withstand the pressure. I tried to look it up for confirmation, but my Googlefu wasn't up to par: I think that at the same pressure, hydrogen is about ten times lighter than air. So with a vacuum, you lose the pressure, and only get a 10% gain.
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  4. #4
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    What's the main engineering challenge to using evacuated cells as a "lifting gas" for lighter than air vehicles?
    I'd have https://en.wikipedia.org/wiki/Newcom...spheric_engine or rather what makes it work as the bigest problem

    Mark

  5. #5
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    Graphene is strong in tension, but that is not what is required for a vacuum balloon.

    A graphene balloon that you connected to a vacuum pump would simply suck down to nothing, just like a vacuum packing bag. It would be useless.

    On the other hand, if we are talking about something like a zeppelin, maybe graphene would make a suitable skin material. it would still need a strong internal bracing structure to take the large compressive load.

  6. #6
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    Yeah, the nice thing about balloons is that they need only to sustain tension. Poke them, and they'll bounce back into shape, within their elastic limits. But a vacuum container needs to be strong in compression, and will have a failure mode involving buckling - poke it, and it not only stays poked, it collapses.

    Grant Hutchison
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  7. #7
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    Carbon fibres are strong in both tansion and compression , graphene too, so a small sphere could hold a vacuum but as size increases you get the conditions for local collapse. You see the effect in underwater vehicles, its the same as an atmosphere sub at 10 m depth. Possible in several materials but then to be both large and light enough is tough. Hydrogen supplies pressure at a small mass penalty so that is easier to imagine.
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