[GCARC] Test balloon

[Jon Pearce]

Thanks to Jeff for the ongoing updates. We had an exciting day doing the final prep and launch of the balloon. Our pre-launch success criterion was that we’d be happy if we could track the balloon up to 10,000 feet. It reached twice that altitude before starting to drop. At that point our “revised” criterion was that it would reach international waters before dropping into the ocean, which it also did.

A critical decision in the design of this launch was that we’d leave open a small soda-straw port on the bottom of the balloon to allow gas expansion as the balloon rose. We did this because the balloon was Mylar and wouldn’t stretch; instead it would burst. Our assumption now is that the balloon reached a height at which much of the helium was forced out of the balloon - too much to sustain constant lift - and that it slowly sank until it hit water. We had unintentionally overinflated the balloon, injecting more gas than was needed to raise the payload, but decided to leave it that way to assist in the lift.

We may do another test sometime this week with the vent on the ballon sealed. This will increase the likelihood of the balloon bursting so we’ll be more careful in filling it. We’ll also be using a battery for power again because of lower cost but also because it provides consistent power to the radios and allows updates every 10 minutes according to the WSPR protocol schedule. Using solar cells might limit transmissions if the balloon isn’t in direct sunlight, and we want prompt telemetry results. We expect this balloon to fail but are interested in seeing its altitude and how far it gets before failing.

The launch that we hope will go much further will use a different type of balloon that’s more costly but also more durable. That’s what we’ll be using for the August 3 launch, weather permitting.

But we had an excited group of hams and visitors in the clubhouse for the three hours of the flight and we hope to repeat that experience many more times as we try different configurations of lift and payload approaches. Jeff is holding space in Crosstalk for some pictures and graphs, and we’ll have more at the next General Membership meeting so stay tuned if you’re interested in this very cool extension of ham radio.

73 de Jon WB2MNF along with Mike KG4JYA and Doug KD2VQA

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________________________________
From: gcarc-bounces at mailman.qth.net <gcarc-bounces at mailman.qth.net> on behalf of Jeffrey Garth <djgrath1 at gmail.com>
Sent: Saturday, July 20, 2024 2:26:50 PM
To: GCARC Members <gcarc at mailman.qth.net>
Subject: [GCARC] Test balloon

All,
It looks like the balloon has dropped in the ocean. Good job for our first
test!
Now we learn from this and launch another one, maybe next week!

Jeff WB2ZBN
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