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[aprssig] Balloon warmth

Robert Bruninga bruninga at usna.edu
Wed Mar 24 00:20:47 UTC 2010


> but it looks like the payload froze 
> before it got very high.

In most cases, this can be easily avoided.  Once a balloon
payload clears the clouds (if any), there is more sun up there
than one will ever feel on the hottest July day.  The mistake
frequently made is insulating it in white styrofoam and
completely BLOCKING the sun, reflecting most heat gain, and
insulating the package from any heat gain on the skin.  Thus,
THREE things being done to make sure it gets COLD. (Only the AIR
is cold, not the 100 Watts of heat falling on every square foot
of the package from the sun...)

There is no reason for cold balloon payloads.  My only flight
more than 15  years ago was in a shell of two clear plastic coke
bottles and then all one has to worry about is overheating it!
We launched at about 70F and the temperature only went up as it
flew.  Problem was, we had listened to too many other
balloonists and calibrated our thermister to only go DOWN from
70F, and so the temeprature data was saturated above about 100F.
We just know it never got colder than when it launched.  And it
went to 100,000 feet.

There is PLENTY of heat up there, just let it in!
At least paint it black...

No reason to get cold in bright sunlight!

Bob, WB4APR





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