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Ascension rate of balloon

  1. Jun 12, 2010 #1
    How do I find the accelerating ascension rate of my helium balloon?
    Ignore factors such as the increase of volume as it ascends, temperature, wind etc.
    I just want the basic ascension rate of ideal non changing conditions.

    rho_f Outside air density - I think typical air density is this - 1.2 kg/m^3

    v Volume - 179.59438 m^3

    m Mass - 90.7184 kg

    g Earth's gravity - 9.80665 m/s^2

    Through some research I have been given this formula but am not sure if its the correct one or how to compute it.

    a = g*(rho_f * V - m)/(rho_f*V + m)

    And also this link

    http://en.wikipedia.org/wiki/Buoyancy#Beyond_Archimedes_Principle
     
    Last edited: Jun 12, 2010
  2. jcsd
  3. Jun 12, 2010 #2
    For a non-accelerating ascent, the upward force of buoyancy will be balanced by a downward force due to air friction.
     
  4. Jun 12, 2010 #3
    (edited) I meant the accelerating rate, sorry
     
  5. Jun 12, 2010 #4
    OK. Use the T=ρfVg-mg equation from your Wikipedia article to find the initial upward force.

    The initial acceleration is then, ai=T/m.
     
  6. Jun 12, 2010 #5
    So if I did this correctly the answer is: 13.490311 m/s^2 ?
     
  7. Jun 12, 2010 #6
    That's the answer I get.
     
  8. Jun 12, 2010 #7
    Giga-thanks!
     
  9. Jun 12, 2010 #8
    How would I find the constant non accelerating ascent due to air friction? haha
     
  10. Jun 13, 2010 #9
    Under Mechanical Engineering there's a Aerospace Engineering subfolder. I take it this balloon would take the shape of a teardrop, flattened on the nose, with a lot of wrinkles. I'm not touching that one.
     
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