[aprssig] Coast-to-Coast Balloon Flight (non-burst?)

[Jason KG4WSV]

On Thu, Dec 15, 2011 at 7:21 AM, Bob Bruninga <bruninga at usna.edu> wrote:
> Or was it oversized simply so that it would not burst?  I'd like more info
> on what prevented bursting...

A latex balloon normally bursts due to pressure differential, but you
can reach equilibrium if you don't stress it too much.  This is
usually accomplished with a combination of an oversized balloon, light
payload, and low fill/slow ascent rate.

For example, our flights are typically ~10 to 12 lb payloads, 1200g or
1500g balloons, and ~1000 ft/min ascent rate.  This generally gives us
a burst of well under 100k'.  The burst is due to the pressure of the
lift gas on the balloon envelope exceeding the balloon's strength.

If we used a 2000g or 3000g balloon, an 8oz payload, and a 300 ft/min
ascent rate we'd get a higher burst altitude and a good chance of
reaching that equilibrium pressure that results in a "floater",
because the lift gas pressure reaches equilibrium with atmospheric
pressure before the lift gas pressure exceeds the envelope's strength.

UV also damages the latex, reducing the maximum pressure it can
contain.  These guys launched late and avoided several hours of UV
exposure.

-Jason
kg4wsv