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2185Re: [GPSL] The mystery of the near constant ascent speed

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    Apr 1, 2006
      I tried looking at the drag equation and seeing if I could show the
      balloon's speed should be constant. But I kept coming up with a speed
      that was not constant. I'll see if I can find my notes and show my


      >>> manes@... 3/24/2006 9:57:24 pm >>>
      Hi Hank,

      Well, like so much other technology that's been once well-understood
      and slowly forgotten (like the MIT Series), I'd be not surprised if
      somewhere lurking out there is a paper which precisely describes
      latex balloon ascent behavior.

      Sounds like a great topic for an aero engineer's master's thesis!

      Any takers?

      73 de Mike W5VSI

      Hank Riley wrote:
      >>We were deep in to Reynolds and
      >>Grashof numbers and finally decided that the only way that this
      >>phenomenon can be explained is to allow the shape of the balloon
      >>to deviate from a sphere over the ascent course.
      > Mike,
      > I guess that it just has to remain a mystery with a plausible
      > but not rock solid explanation if you guys didn't solve it.
      > Also my derivation that had the balloon either speeding up
      > or slowing down with increasing height (guessing it was the
      > former) was okay as far as it went, making the usual
      > assumptions. It's just that the basic model is missing
      > something, like the variable shape factor you mention.
      > It still amazes me that the ascent speed seems to adhere as
      > well as it does to a constant. There are a good number of
      > anomalous amateur flight logs, but I believe the vast majority
      > are really pretty steady from liftoff until burst.
      > Hank
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      Mike Manes manes@... Tel: 303-979-4899
      "Things should be made as simple as possible, but not more so." A.

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