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Thread: Helium and Hydrogen balloons

  1. #1 Helium and Hydrogen balloons 
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    Before helium, balloons filled with hydrogen were used. Now that helium balloons are in use, how is it that He, that has twice the density of H, provides the same lift as the same volume of H ?

    Can I have a proof ?


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  3. #2  
    Forum Senior silkworm's Avatar
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    Who told you it had the same lift? I never knew that, I thought the tradeoff was because of things like the Hindenberg.

    Helium's advantage is that it's pretty inert. and that's a bit of an understatement.


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  4. #3  
    Forum Professor Zwolver's Avatar
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    no, Hydrogen has more lift.. if compared it's a lot more lift.

    i don't know how much it differs anyway..
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

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    for silkworm's question - "who told you that ?", i found this in a book by a russian physicist - V. N. LANGE. there is a particular question in the book that demands for a proof, so.
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    Forum Senior silkworm's Avatar
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    Helium and hydrogen both provide about 1 kg of lift per cubic meter of gas at room temperature and sea level pressure. Although hydrogen is slightly more buoyant, helium is usually preferred because it is not flammable.
    http://en.wikipedia.org/wiki/Lighter_than_air


    Maybe it has something to do with the leakage vs. molar mass, or that while He is twice as dense as H2, you'd only use half as much, and it would still be much less dense than air.

    That's the best I can think of right now, but I'm pretty groggy.

    I've never heard of Lague, is it a textbook in spanish?
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  7. #6 Re: Helium and Hydrogen balloons 
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    Quote Originally Posted by eurekalert
    Before helium, balloons filled with hydrogen were used. Now that helium balloons are in use, how is it that He, that has twice the density of H, provides the same lift as the same volume of H ?

    Can I have a proof ?
    It’s not exactly the same lift, it’s just very close. The amount of lift is equal to the mass of air that the balloon displaces minus the mass of the gas that you’re displacing it with. The density of helium is 0.18 grams/liter while the density of hydrogen is 0.09 grams/liter. The density of air at sea level is 1.3 grams/liter. So although the relative difference in density between hydrogen and helium is large, they both have a very small density compared to the air that they are displacing.

    A helium balloon will give you a lift of 1.3-0.18= 1.12 grams/liter while a hydrogen balloon will give you a lift of 1.3-0.09= 1.21 grams/liter.
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