ThunderStruck – Backup Preparations
Jason, our 12 year old pilot is no stranger to having to prepare for the worst and it is what we do every time we send up a payload. Our last flight of a balloon into the stratosphere was a case of just that. Two failures. One on launch and the second on decent. Each problem would be enough to cause most balloon payloads to be lost, but as part of our preparations, we carried two trackers for the one flight. This was a flight in preparation for our project and we are testing. We have had to cover our payload in the video. Our apologies.
Below: An artist’s view of the ThunderStruck aircraft under a zero pressure balloon (more on that another time) at 40km altitude. You may have guessed, I am the artist….. Note that on the ThunderStruck event, we will not be using weather balloons so there will be no unexpected explosions.
The first failure was totally invisible to us. A massive downdraft. The first that we have ever encountered. Uplift-1, our first flight, started in an updraft and it rose at an incredible rate for the first kilometre. In the video below, you can hear me make the comment that there did not appear to be the lift that we knew we had because we had used scales to measure the lift. We could not feel the downdraft pushing the balloon down 15 metres above our heads. I mistakenly thought my lack of “feel” was because of the others also holding the payload. We released the payload and balloon and then our hopes sank as the payload only lifted slowly and then sank back to the ground. We ran to catch it, but it rose again and caught on the edge of the eve of the roof of a nearby wheat silo. It stayed there for only 2 minutes, but it felt like an eternity before it released. It rose quickly as calculated, but one tracker had had its GPS unit disconnected and the other had its antenna twisted 90 degrees effectively lowering the power considerably. None the less we could still track the flight – mostly.
One tracker disabled, but still sending its ID at full power, The other effectively made to look low power. Those GoPro cameras are great. hundred of metres above the ground you can hear (faintly) people talking and a dog barking! They make great gear.
The weather balloons are meant to explode and disintegrate. This one did not. The entire balloon, well over 1Kg fell into the parachute and tangled itself in the chute, effectively making the mass look like more like a tangled flag than a parachute. It slowed the payload in the thick air, but the fall from its maximum height was rapid and the entire fall from 30km only took 15 minutes. This was an average speed of 120kph. Given that the payload probably hit the ground at 30 to 40kph, the initial speed was probably close to 400kph in the thin upper air.
With the tracker only giving us effectively a poor signal, the last track that we received in one of the vehicles headed to the landing site was 2 km above the ground making the landing site potentially one square kilometre. We also fond out later that the second tracker was never going to give us a signal, because the impact had caused a battery to eject from its holder. We only had one ID every 20 seconds and no GPS location! We used a directional antenna to lead us to the payload, but it was a slow and painful task.
The video below shows the impact and the wooden spars breaking. The camera continued to record! Nothing like a good wiring system to ensure that power kept flowing from the external battery. I did not mention that we use external batteries. The GoPro’s batteries, even with the additional power pack, just do not last for the entire flight if it goes over 2.5 hours and especially if it is taking both videos and stills – The new GoPros are amazing, but need more power for High Altitude Balloon (HAB) flights.
Initially the video above shows the incredible stability of our payload at 30km altitude. The Balloon explodes at the 30 second mark and then plummets and spins at a sickening rate of a couple of times a second with the disabled chute causing the spin. At 1 minute 45 seconds, we cut to an altitude of about 3km and it took 3 minutes to hit the ground at 60kph. At the 4:45 mark, the payload hits and spars shatter. The camera keeps recording. By the way, the big tree lined road is the Mid Western Highway. The payload was kind enough to land in a sheep paddock beside the main road. You can’t ask for better.
The lesson here is that if it can go wrong, it will go wrong. Yes, we have recovered every payload that we have sent up, but good preparations both in the payload design and build is important as are the preparations for recovery on the ground. We even carry poles to remove the payload from trees. We can manage 14 metre trees. After that we will have to look at other methods.
Our preparations will be backup, backup and more backup. Redundancy rules over weight considerations where possible. Systems will be over-engineered and more care will be taken than what appears necessary. Project ThunderStruck will fly while the world watches. Delays will be unacceptable. This was UpLift-20 and again we have 100% successful recovery rate. @0 flown and 20 recovered. As our flights become more aligned to the actual shape of the ThunderStruck aircraft, speeds will dramatically increase on decent and the videos will have way more interesting stuff to show, but these lessons were there to remind us not to get complacent.