9/14/2019 Balloon Post-Flight Review


  On September 14, 2019, the West Georgia Amateur Radio Society launched a high altitude weather balloon from the VFW Fairgrounds in Carrollton, GA. This was our second weather balloon launch this summer. 



  Because we wanted to have a camera facing down we had to use a new payload container. This one seemed to be a good bit thicker, which added to the weight. Read on to see how that became a factor. This payload also included the APRS tracker and crossband repeater, both designed and built by WX4BK. It also included sensors to measure and log internal and external temperature, humidity, barometric pressure, UV, and G forces. 

Flight and Performance

  This is where it gets interesting. Even though the helium tank was the same physical size as before, we were told that it held 250 cubic feet of helium. We'd used it on the last flight. Assuming that it really held 250 cubic feet, we should have had enough for this flight. I should have gone with my gut instinct that it held 219 cubic feet. We inflated the balloon, tied it off...and discovered that we did not have enough helium to lift off. KM4UPX came to the rescue by getting a tank of helium from the First Christian Church in Carrollton. I continued with inflation until I got 5 pounds of weight neutrally buoyant, assuring that we would have an ascent rate around 1,000 feet per minute. 

  Once again, things inside the payload got really hot. When I picked up one of the cameras at the landing site, it was too hot to hold. We had some problems with sensors dropping out or reporting incorrect data. I'm wondering if heat was the cause. The crossband repeater was another mystery. It worked on the ground, but was sporadic in the air. Brian thinks one side may be desensing the other, but it's interesting that the problem doesn't always happen. The APRS functionality worked perfectly through the flight.

  You can see two flight predictions (800 feet per minute in blue and 1,000 feet per minute in red) as well as the actual flight path in green. It appears that I inflated to slightly more than 1,000 feet per minute, which turned out well. It kept us out of the Talladega National Forest, but still landed us in a remote area. 


  Once again, recovery was an interesting experience. Referring to Alabama county roads as "roads" is a bit of a stretch.

  You know it's an interesting "road" when you have to get out of the truck to plan your route through that section and see if it's even possible. At one point, KK4OHF and I had to stop and wait for goats to cross the road.

  At the landing site, I stayed with the truck and monitored the radio as the teams set out through the scrub and thorn bushes. I had planned to take my drone up to survey the site and potentially spot the payload. I did get it up in the air, but had a moment of panic when my tablet, which I was using to control the drone, had a thermal shutdown while the drone was in the air. Fortunately, the drone descended, and I hand caught it. Shortly thereafter, I heard cheering in the distance and confirmed on the radio that they had located the payload and were in the process of trying to recover it. It had landed across a creek in some scrub brush. The guys watched as a member the self proclaimed "girls team" waded across the creek and pulled the payload down. Upon examining the footage from both cameras, I discovered that we had apparently bumped the record button on the downward facing camera and turned it off just as we were putting it into place. It's an easy mistake to make. We'll just need to cut more of a slot in the payload to leave room near that button. All in all, I think it was a completely successful flight. The APRS worked flawlessly, everyone had a blast, and we recovered the payload soon after landing. Not only that, but we once again caught burst on video.

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