- Details
- Written by: Blake Raab (N4BWR)
- Category: Balloons
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.
Payload
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.
Recovery
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.
- Details
- Written by: Blake Raab (N4BWR)
- Category: Balloons
Launch day is upon us!
Launch day predictions are 40 miles with an ascent rate of 800 feet per minute, and 30.5 with an ascent rate of 1,000 feet per minute. I strongly encourage you to take a look at the map here and familiarize yourself with both predictions and how ascent rate changes those predictions.
- Details
- Written by: Blake Raab (N4BWR)
- Category: Balloons
On July 13, 2019, the West Georgia Amateur Radio Society launched a high altitude weather balloon from the VFW Fairgrounds in Carrollton, GA.
Payload
This was a 1200 gram weather balloon, and we used helium. The payload, which weighed 2.5 pounds, consisted of a crossband repeater and an APRS tracker, both custom designed and built by WX4BK. It also included two cameras. They were a Lightdow LD4000 that would point up at the balloon to catch burst on video, and a GeeKam that would point out the side to catch video of the flight.
Flight and Performance
We arrived at 9 AM and began preparations shortly thereafter. Balloon inflation was very easy and quick, thanks to the trusty inflation kit consisting of a hose with a CGA-580 brass fitting on one end, and a plastic piece on the other that fits nicely into the neck of the balloon. I'm still going to need to find a reliable and accurate way to measure neck lift. I needed an amount just under the maximum for the lift scale I was using, and the breezes made it difficult to judge that by providing artificial lift. We ended up with an ascent rate that reached just over 1000 feet per minute at times, which actually worked out well.
We had planned to connect the cameras to external power through the charging port so they could last the whole flight. The camera pointing up turned out to have a bad connection on the charging port, but somehow managed to survive long enough to catch burst and 20 minutes of freefall. I'm still not sure how that happened. The other camera, which did get to be connected to external power, covered the whole flight (and an hour of watching ants and bugs crawl on the leaves and branches that we landed on).
Leading up to launch, we had several minutes of panic, because nobody, even those on-site with equipment, was picking up any APRS telemetry from our payload. We reset the system and it started working. After that, the APRS unit worked flawlessly in flight. WX4BK was able to receive data from his home IGate from right after launch to near landing, while the payload was only transmitting at half a watt. Upon launch, we discovered that the crossband repeater seemed to have a faulty VHF module, so it was quickly decided to stop trying to use it to conserve battery for the cameras.
The balloon burst at 109,872 feet (which we caught on video) and descended rapidly. In the high altitude environment, there is almost no air, and therefore, very little aerodynamic drag to deploy the parachute. Because of this, the payload can tumble and spin wildly, all the way down to 50,000 feet. We had already lost a payload two years ago when it is believed that the antenna ripped off during this tumbling and spinning. We had another moment of panic on this flight when we lost telemetry for three minutes. We believe that the rapid spinning made the GPS briefly lose satellite lock.
Because I had slightly overfilled the balloon, we ascended more quickly, resulting in a lower burst altitude and a shorter flight distance than predicted (Play with the numbers in the CUSF Landing Site Predictor to see how those factors change things). We descended toward rural Alabama and an area where the only roads are county roads. That turned out to be quite an experience.
Some people seem to think that we failed somehow or that we encountered something unexpected when the payload stopped being received by IGates. In fact, this did not even happen until it was around 3000 feet above sea level, which was 1500 feet or less above ground level. This is to be expected. It was only transmitting on half a watt through a wire hanging below the payload. Once we got below the trees, it was not going to be received. This is why we run flight predictions and go to the anticipated landing site. Once we were near the last beacon point, we were within 1000 feet of the payload and could pick up the signal directly. The shape of the flight path stayed the same as the prediction. The only adjustment was to the ascent leg, since we had a higher ascent rate. Here is the predicted flight path compared to the actual flight path. The speed upon landing was within four feet per minute of what I wanted it to be.
Overall, it was a completely successful flight. There were lessons learned, and getting the full flight video and telemetry data certainly helped with that.
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- Details
- Written by: Blake Raab (N4BWR)
- Category: Balloons
APRS tracking is available here.
ICS-205 Incident Radio Communications Plan
The West Georgia Amateur Radio Society will be hosting another weather balloon launch this Saturday July 13, 2019. We will plan to meet at 9 AM at the VFW Fairgrounds in Carrollton. The address is 1625 Bankhead Hwy, Carrollton, GA 30116. Obviously, this event will be dependent on weather, so we will have to wait and see as the week progresses.
We will meet at 9 AM and begin preparations and inflation. Launch will happen whenever it's ready. We can't really narrow it to a specific time, but it will probably be between 10 and 11. After that, we will begin chasing the balloon, which will be carrying an APRS payload to transmit its location and altitude in real time. It will also carry a crossband repeater so we can communicate with each other through the balloon. The balloon will be a 1200 gram weather balloon this time. We have used 800 gram before. Using the larger size, along with hydrogen, we anticipate reaching an altitude near 113,000 feet. Predictions have the balloon going west into Alabama. Distances depend on exact conditions at the time.
I will update this article after 7:45 on the 13th with a map of the prediction as well as predicted landing coordinates. I will also give a briefing on that information at the launch site. If you plan to chase the balloon, please stay in contact with the other chase teams through either the W4FWD repeater or the balloon's crossband repeater, wherever you can reach us. I may update predictions on the fly based on variations observed in our ascent rate, and I don't want anyone to still be heading for the other predicted landing site if there is a change.