Balloon Launch - Friday Evening

This is the balloon project I mentioned at the Hack Space


JonFrom: James Coxon
Date: Monday, July 20, 2009
Subject: [london-hack-space] Balloon Launch - Friday Evening

Yes the launch went ahead, actually 2 launches went ahead. On friday
we launched a little late, unfortunately the balloon didn’t achieve
float as its ascent rate was too fast, it reached about 35km altitude
(not exactly sure due to a code issue - oops!) and then burst and
parachuted down. Managed to recover it from a field near Haverhill at
about 1am.
Managed to find another balloon, sort of fixed the code and so
launched on Saturday evening, this time with a much slower ascent
rate. Managed to get the balloon to float at 27km for 7hrs 15mins.
During this time the GPS got so cold it lost lock but through the
night we had a strong radio signal just no valid data. With the
sunrise it warmed up the payload and the GPS sorted itself out and
started sending valid data. The heat from the sun made the helium
expand and the balloon burst soon after sunrise, the payload
parachuting down just north of Stoke on Trent.
Overall it was a great success - the 2nd flight perhaps a little more
then the 1st!

Lots of info can be found here:
including some graphs and links to pictures.