The High altitude ballooning group launched 2 small balloons,ICSPACE6 and 7 today, 9 March 2019 from Wormwood Scrubs, London with trackers on board. We successfully tracked them all the way to Belgium but they mysteriously disappeared over what I now call the “BelgiuMuda Triangle”. This was the highest flights we have flow with these small balloons, reaching a max altitude of 8697m and the coldest temperature reached, -22°C. Due to the terrible cold we saw some spectacular frequency drift on the telemetry frequency. Next time, we need to put a TCXO on.
It’s also the first flight to overfly 3 countries: UK, France, Belgium. The top speed was over 230km/h due to the incredible winds blowing from the west, and the balloons covered the distance in around 3 hours.

On further analysis, it is likely that local weather conditions caused the trackers to stop transmitting. According to Chris Stubbs, in his tests with the RFM22B which uses the Si4432 which is from the same stable as the Si4463 which we use on the HC-12 module, he notes that while cycling between temperatures between 20°C and -50°C the chip stopped transmitting “as the temperature passed about -10°C”. He suspects it could be condensation that could be messing around with the chip. In future launches we will conformal coat the electronics.

Key information:
balloon: Qualatex 36 inch
payload weight: 17.7g
net lift: 4.5g

balloon: Qualatex 36 inch
payload weight: 17.7g
net lift: 4.5g

Here is a video of ICSPACE7 at launch. It nearly got stuck in the tree behind us right after launch. At the 28s mark it did a Loop de loop. 

Here are some photos of the trackers.

Flight path of ICSPACE6 and 7

close up of GPS module and antenna

close up of telemetry antenna

Before embedding the components in the polystyrene

getting an idea of how big the components are

The internals of the trakcer. Note the GPS antenna on the left and telemetry antenna on the right of the image.

The tracker suspended in air

Total weight of the tracker fully packaged is 17.7 grams

A pair of trackers, ICSPACE6 and 7, ready to launch.