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Weather Ballons, APRS, and Simplex for JOTA

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  • Phil Sohn
    This year we did something a little different. We launched and chased a weather balloon with an OpenTracker for JOTA this year. It travelled from Woodinville,
    Message 1 of 1 , Oct 18, 2011
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      This year we did something a little different. We launched and chased a weather balloon with an OpenTracker for JOTA this year. It travelled from Woodinville, WA to Bridgeport and was in the air for 2hrs and 10 minutes. By the time it was over Duvall 25 minutes after launch, it was 17,168 ft high. It reach 115mph at 38k ft. The highest recorded point is 65,138 ft which is in the stratosphere and the ozone layer. That is almost 20km up. It was about -55 degrees C when the balloon burst. It didn't make it any higher because I underestimated the weight of our payload by a fair amount. We only had a 350gram balloon. We needed to fill it past the recommended point because of our payload.

      The first attempt had a small hole in the balloon. It didn't get enough lift. So we just let it go without a payload and watched it disappear into the clouds. The boys also went through 81 cubic feet of helium to fill 40 cubic feet in the balloon. Not sure how much escape through the whole and how much escaped because the boys didn't have a tight enough fit between the balloon and the tank. You always need a fudge factor when dealing with 14 year olds. We went and got another tank of helium for the second balloon, and tied the balloon to the tank to prevent leakage.
       
      I've posted some photos here including the flight path and the predicted flight path. The predictions were based upon an ascent rate of 5 m/s, but we only averaged 3. That is why we went so much farther. The longest 2M radio path was Canada up by Ft Langley to Lake Chalan, WA 136 miles away.
       
      An edited video capture by the camera on the balloon is here:
      http://www.youtube.com/watch?v=QAxZhCrlyzg. It is posted by a boy who is an aspiring videographer. He is working on a more complete video which should be ready in about a week.
       
      You can see the track here for the rest of this week: http://aprs.fi/?call=K7APS-11&mt=roadmap&z=11&timerange=3600&_s=ss_call
       
      The kids had a great time tracking the balloon on APRS and the internet as well as talking to each other on simplex during the flight. We lost the direct signal from the balloon while we were on the road around Stephens Pass. It was nice to be able to see it on the internet once we got close to Leavenworth. But the last recorded signal was at 4,051 ft where the terrain is only 2,000 ft high. So we were a bit concerned about being able to find it. But once we got on top of the plateau where the last signal originated, we picked up the Argent Data Open Tracker signal and were able to drive within 1/4 mile of the parachute. We were able to see if from the road. The boys were ecstatic could barely wait until the rest of the patrol arrived before running to recover it.

      Phil
      K7APS
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