LoRa Balloon flights to Austria and Slovakia

The High Altitude Ballooning Group launched two trackers on 31 January 2020 from Fryent Country Park. ICSPACE16 was last seen over Austria while ICSPACE17 landed on a hill in Slovakia and was transmitting until it ran out of battery.

Flight path of both balloons

ICSPACE16 was our first pure solar tracker, with 6 solar cells generating a voltage of ~3.6V. We launched under cloudy conditions and thus it did not have power at launch. ICSPACE16 first appeared the next morning when the sun came up at an altitude of 9300m, the highest we have reached. However, it transmitted its position twice at sunrise and was silent for the rest of the day. During sunset, due to a reset caused by the low incidence angle of the sun(and thus lower solar voltage), the tracker came to life and transmitted 5 more fixes. It was just about to enter Hungary. It is likely that a software issue was behind the low performance of tracker. The software was not very robust in handling unexpected resets of the GPS and microcontroller. Sadly, this was the last time we heard from ICSPACE16.

ICSPACE17 was battery powered, with an Energizer AAA battery+ boost converter. The transmissions were picked up by 100s of gateways connected to The Things Network here in the UK and in the Netherlands and over Europe. It flew overnight to Slovakia. However, in the morning, when the sun came up, due to heat from the Sun, the balloon shot up by 2000m before bursting and coming down. It was still transmitting for the rest of the day and was picked up by a gateway mounted on a radio tower. For a while, our tracker became a weather station, reporting back temperature and pressure on that hill in Slovakia. How cool is that!

Flight profile for ICSPACE17 shows rapid altitude rise at the end before bursting and coming down quickly!

Like our last flight, the tracker used LoRa radio transmissions that were picked up by the 100s of gateways connected to the Things Network. On board our tracker was a custom 0.6mm PCB integrating the CMWX1ZZABZ-078 LoRa radio module, U-blox MAX M8Q GPS, TE Connectivity MS5607 temperature/pressure sensor and boost converter. All the design files and software can be found on Github.

We are thankful to everyone who setup their LoRa gateway and connected it to The Things Network. In our code, we have implemented Geofencing to switch radio parameters, depending on local restrictions.

All our circuits are designed on Kicad, which is very flexible.

We then make a PCB design with Kicad as well.

Assembly of the trackers were done either in the Undergrad electronics lab at Imperial College London or the well equipped Imperial College Advanced Hackspace.

The Aliexpress party balloon was prestretched by filling it up with a vacuum cleaner. The tube was attached to the outlet where air came out. Our vacuum cleaner had two ports to connect the tube to. One was the suction end while the other was the blower end.

ICSPACE16
balloon: Aliexpress party balloon
payload weight: 6.0g
net lift: 5.5g
float altitude: 9300m
max altitude: 9345m
distance traveled: 1287 km
flight duration: ~23hours
Lifting Gas: Party balloon helium(not very pure)

ICSPACE17
balloon: Qualatex 36 inch
payload weight: 12.0
net lift: 6.5g
float altitude: 7400 m
max altitude: 9391m
distance traveled: 1481 km
flight duration: ~18 hours
Lifting Gas: Party balloon helium(not very pure)

Photos of trackers and launch

Just before launching ICSPACE17

Plenty of gateways picking up packets

Landing site of ICSPACE17

Solar cells in the sun