In article , Mike Coslo writes:
Does other odd things too. Bouncy, bouncy!
Space, or near space is a very strange place...
'Cause it's hot? ;-)
If it wasn't hot, we wouldn't have the ionization that allows us to
communicate all over the world on HF.
bouncy bouncy
You *don't* understand some *very* basic
things about the atmosphere, things that you should know as a Ham.
This whole thread got me thinking about how balloons work and how much
helium
costs and such. One thing I found out is that 1000 cu ft of helium can be
had
for about $200. A bit of $$ for an individual launch but not much if split
up amongst a group.
And of course you don't need that much per typical launch.
So the cost is even less.
Another thing was the lifting power at high altitudes and low pressures,
and
the concept and behavior of a balloon open at the bottom that's not filled
all the way with gas. Fascinating.
Those balloons get BIG before bursting. I've seen some video of it. I
haven't seen what happens to the form of the zero-pressure balloons,
though. Certainly the zero-pressure balloons are a fascinating example
of a self regulating system.
With a closed rigid balloon (like the Hindenberg), the lift gas is at constant
volume, so the lift decreases with higher altitude and lower barometric
pressure and the maximum altitude is relatively low.
With a closed elastic balloon (like a stretchy latex balloon), the lift gas can
expand to a certain degree at higher altitudes, but must be at somewhat higher
pressure than the gas outside (because the gas inside must exert pressure on
the balloon walls to stretch them). With a very stretchy balloon, the decrease
in lift will obviously be much less than with a rigid balloon.
With an open-at-the-bottom balloon (like a bag from the dry cleaners), the lift
gas need be only at a very slightly higher pressure than the gas outside
(because the gas inside must support the walls of the balloon/bag). With a bag
that is much larger than the volume of gas at launch, the decrease in lift will
obviously be much less than with a rigid balloon or a stretchy balloon.
73 de Jim, N2EY
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