The flight path of ICPACE5 that landed in the Netherlands.

On the 6 Feb 2019, the High altitude ballooning group launched 2 Pico balloons,ICSPACE4 and 5 from Wormwood Scrubs, London. ICSPACE5 travelled a total of 386.52 km and reached a max altitude of 6290m. However, ICSPACE4 travelled a grand total of 500m and the peak altitude of the top of the tree at the edge of Wormwood Scrubs.

The hardware was almost the same as in the launch 2 weeks earlier. A HC-12 module with the Silabs Si4463 radio chip, STM8 microcontroller, theGB1803 GPS module, AAA lithium battery and boost converter. This time we used a much lighter boost converter though.

We managed to bring down the weight of the trackers to 14 g, a good 9 gram reduction from the trackers we launched the last time. ICSPACE4 and 5 were launched with a net lift of 2g and 3g respectively. The key improvements were:

1. Using a lighter boost converter. The boost converter used in ICSPACE2 and 3 had retaining clips for the battery and was assembled on a PCB. This time, we used an off-the-shelf Boost Converter with exactly the same components but without the PCB backing. The form factor was much smaller.

2. We removed the 3D printed frame that was really very useful in testing the components. Richard Ibbotson designed an excellent 3D printed frame for all the components. It was really useful in testing because Richard also designed a clip with pogo pins that connected to the programming lines of the STM-8 chip on the HC-12 module. The clip was detachable. However, in flight where ever gram mattered, we had to remove the 3D printed frame and instead embedded the components in the Polystyrene instead. The polystyrene provided the structural support, saving 3-4 grams in weight. The weight of the 3D printed part was shaved off in these flights.

The wind was incredibly strong on Launch Day and unfortunately ICSPACE4 never got enough altitude to clear the trees at the end of the park and is to this day still stuck there. The wind had not really died down during the launch of ICSPACE5. However, there was a slight lull in the wind for a brief moment and we released it. ICSPACE5 quickly made it to the east coast of England in around 1 hour.

The flight was not without problems. I had set the GPS to transmit its position only when it got a good fix of a minimum of 6 satellites. However, in the air, it could not get 6 satellite fix so it did not transmit its position for long periods of time. Occasionally it came back to life, giving an update on its position. In retrospect, I should have set it to transmit as soon as it got a 3D fix.
This launch, we fixed the baudrate problem that was present in the previous flight .

After it made it over the Netherlands, all of a sudden, we saw the balloon rapidly losing altitude. The last fix was around 300m over ground. We thought that was the end of that balloon. However, Dutch radio amateur Joal PD3JO actually travelled the area it was expected to land at, managed to get a fix and FOUND THE BALLOON!
At this point, we are looking forward to seeing what happened to the balloon. He has told us that there must have been a tiny leak somewhere because the balloon was still inflated when he recovered it.

Key information:
balloon: Qualatex 36 inch
payload weight: 14g
net lift: 2.0g

balloon: Qualatex 36 inch
payload weight: 14g
net lift: 3.0g

Thanks to Ryan White of the Imperial College Advanced Hackspace for coming to the launch as well as filming the pre launch preparations.

All the components placed on top of the foam before carving out the cavities.

The GPS module and HC12 module in place. Note the Guitar wire antennas for the GPS.

The mass of the Empty polystyrene. An amazing 1.07g

Testing the GPS tracker outdoors.

Total weight of the sub-15g tracker

Components all embedded in the Polystyrene