Launch Day 9/14/2019

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.

We will mainly be using the W4FWD repeater until it is out of range. Then we will switch to the WB4GNA repeater on 147.090+ with a 131.8 hertz tone.
 
You can track the balloon online here.
 

Balloon Post-Flight Review

  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.

Weather Balloon Launch - 7-13-2019

 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.

Balloon Planning and Data Dump

This will just be a random assortment of data and thoughts for planning the next weather balloon launch

1200 gram balloon from Amazon (or this one) We've been using 800 gram, but can't achieve 100,000 feet with that  
CUSF says we can achieve 110,813 feet with a 3 lb payload, or 107,290 with 4 lb.    
Hand warmers, perfect size to put behind cameras    
Lightdow LD6000 camera ($42 with SD card)    

 Payload Mass = 1814 grams

Balloon Mass = 1200 grams

Target Ascent Rate = 4 m/s

Burst Alt. = 32808 meters (107,638 ft)

Time to Burst = 137 min

Neck Lift = 2514 grams (5.5 lbs)

Volume = 127.8 cubic ft

(Data from habhub burst calculator)