Saturday, April 14, 2007

Recap of 15 March 2007 zero pressure flight

On 15 March 2007 we launched a small balloon carrying an APRS tracker and 10 meter beacon (beacon built by Pierre Thomson) from the grounds of the Academy to kick-off the fifth grade balloon project.

This unnamed balloon (not part of the Sky Diamond series) was a tetroon made from .35 mil high density polyethylene with a trailing appendix used for both inflation and as a vent. The envelope was small - only about 300 cubic feet and reefed down to about 250 cubic feet - and was designed for a jet stream level float. Helium was used to partly inflate the balloon and it was launched with help from the Academy maintenance department (thanks to Chris, Kevin, Norm and Jon!) into a windy sky.

Designed to float in the jet stream at around 28,000 feet, the balloon was launched with a dribble ballast device to avoid overshoot and early flight termination. It also carried a timer-activated ballasting system designed to drop liquid ballast around sunset, but this device failed due to a faulty electrical connection.

It was clear immediately after launch that the APRS tracker was not working - no position updates were available via Findu or other sites. Bill Brown later discovered that APRS packets were, in fact, being relayed into the tracking network, but no valid position was being reported from the onboard GPS. By watching which digis were relaying the packets to the network, however, a general estimate of the balloon location could be made.

The last packets were received by stations in St. John, New Brunswick and southern Prince Edward Island, Canada, and it was determined that the balloon was clearly descending by mid-evening. A search was then on in the most likely landing zone as determined by Bill Brown - south of Moncton, New Brunswick.

A couple of days passed without any reception reports and we became quite convinced that the balloon had actually landed in the water (perhaps the Atlantic). Then, on 20 March, news was relayed to Pierre Thomson that Reed Park, VE1NU in New Brunswick, had heard the 10 meter beacon! Reed later searched the area along with Mike MacDonald and found the intact payload and shredded balloon (photo links to follow). It was recovered and returned to us at the Academy a week or so later.

Many thanks to Pierre Thomson, Bill Brown, Reed Park, Mike MacDonald and the many, many others who helped to make the tracking and recovery of this flight possible!


Zero pressure helium tetroon
250 cubic foot envelope capacity
APRS and 10 meter beacon payload (~1.5 kg)
500 g dribble ballast
500 g timer-controlled ballast (not dropped)
Launched from the grounds of the Grosse Pointe Academy, Grosse Pointe Farms, Michigan
Recovered near Moncton, New Brunswick, Canada by Mr. Reed Park

Satellite image of recovery location and pictures from recovery, including Reed Park and Mike MacDonald. No pictures of the launch are extant.