How I sent a Raspberry Pi into near space
Last summer was a busy one for me. Contrary to popular thought, for many school teachers the summer holidays aren’t an eight-week jolly but a time for refilling knowledge banks and looking at new ideas.
My new ideas revolved around the Raspberry Pi, and I found myself in the privileged position of taking part in two major training opportunities. The first was to become a Raspberry Pi Certified Educator, a feat I achieved mid-July, and one I thoroughly recommend to any teacher thinking about doing any work with this brilliant little powerhouse of a computer.
A day or so after the course had finished I was in the doldrums. The days had been so full-on, so exciting and so enriching that I was at a real low. I retreated to my den, where I surrounded myself with jumper leads, add-on boards and the brilliant book Adventures in Raspberry Pi by Carrie Anne Philbin (education lead at the Raspberry Pi Foundation) and proceeded to embark on a veritable orgy of, how shall I describe it… I know, fun! Because that’s what learning should be.
“I was about to learn how to take my knowledge of what could be done with the Raspberry Pi to new heights. Roughly 20 miles high, in fact.”
Glancing at the forums a few days later, I saw that James Robinson (education developer, Raspberry Pi Foundation) was offering a place on an upcoming course. I leapt at the chance and, following an amazing sequence of lucky events, was the final person given a place on the first ever Skycademy. Excited didn’t quite cover it. I bounced everywhere like an overactive Tigger until the day finally dawned that I could leap in my car and head for Pi Towers, that haven of brilliance and geekdom located in Cambridge.
So, why the excitement, you ask? I was about to learn how to take my knowledge of what could be done with the Raspberry Pi to new heights. Roughly 20 miles high, in fact. We were heading for near space, and what’s not exciting about that?
The idea was sumptuously simple. Tie a Raspberry Pi with a camera to a weather balloon, add some GPS bits and an antenna or two, include a rather brilliant add-on board for near space, make serious use of polystyrene, sticky-backed plastic and some unsuspecting Lego figures, and then launch the whole shebang into space!
That was the easy bit. The hard bit was learning how to do it so that we had some chance of recovering the payload when it finally came back to Earth. How to track it, how to set it up so that all the different bits worked, and how to inflate it.
Teaching the teachers
You might think that teaching other teachers is a scary prospect, but I’ve never found that to be the case. We teach because we enjoy the learning process, so as long as you know what you’re talking about, you’re not going to have any issues. When your name is Dave Akerman and you’re the UK’s leading protagonist of all things associated with high-altitude ballooning (HAB), and you’re an engineer who can create most of the electronic add-ons needed to support the flights – oh, and you’re a standout programmer too – you tend to find people hanging off your every word.
And hang we did. We needed to. Let’s get one thing quite clear. Launching something into near space is trivial: fill a weather balloon with helium, attach a payload and let go. Getting it back in one piece, however, is quite another matter.
“The Civil Aviation Authority (CAA) takes a dim view of people randomly lobbing devices 100,000 feet into the sky”
For a start, the Civil Aviation Authority (CAA) takes a dim view of people randomly lobbing devices 100,000 feet into the sky. For instance, you have to consider where to launch from: launching isn’t allowed around major airports, and you really shouldn’t launch at all if you’re unsure whether your payload will end up landing on a motorway, say, or crowded residential area.
The first day of the course therefore covered more science than I usually care to think about as we delved into the arcane world of the Pi In The Sky (PITS) board, where the PITS software logs telemetry for the LoRaWAN (long-range wide-area network) as well as other sensor data. We studied payload weights, burst altitudes, predicted flight paths, radio telemetry, RTTY, GPS and a fair few other members of the land of the TLA. Oh, and code. Lots of lovely Python code.
But don’t be fooled into thinking this is only about science and tech. Just off the top of my head, some of the disciplines we looked at included physics, chemistry, meteorology, aerology, radio, electronics, aerodynamics, space exploration, geography, marine biology (the payload falls into the sea) and dendrology (payload stuck up a tree).
While that was taking place, we set about designing our payloads. I was part of Team Nimbus, which basically meant I was put in a group full of people with infinitely larger brains than I, so I settled down to choosing the colours for our gaffer tape and drinking straws, as well as choosing the bee (fear not, a fluffy toy one, not a real buzzing insect) we intended to place on the outside of the package.
Why drinking straws, you sensibly ask? Because these protect the payload antennas and help them to point straight down when the antenna module is attached to the base of the payload container.
“Some of the disciplines we looked at included physics, chemistry, meteorology, aerology, radio, electronics, aerodynamics, space exploration, geography, marine biology (the payload falls into the sea) and dendrology (payload stuck up a tree).”
Then we come to testing. It’s vital, for example, that your tracking equipment is able to detect the payload before you launch. You’re then free to leap into the chase car and follow the flight path. So we tested. I’m not quite sure what the residents of Cambridge made of the sight of grown men and women running around the streets outside Pi Towers waving polystyrene boxes in the air, as they checked if they could be detected by the ground station (at Pi Towers) and the car systems. Nobody got arrested, though, so it must have been okay.
The day drew to a close with heads spinning with newly gathered knowledge, as we all headed off for a group meal, and a chance to discuss what we had been doing all day with other team members. Tomorrow was launch day and the weather wasn’t favourable, so we headed to bed in a state of trepidation.
The big day dawned and we headed off to our top-secret launch site at Elsworth, just west of Cambridge. Ground sheets were spread and the gas bottles handed out. Two teams chose hydrogen and three chose helium.
Some careful weighing now followed. Every gram makes a difference. Fortunately, there are a brilliant set of online tools that tell you all you need to know about how much gas is needed for a payload using a specific balloon that you wish to burst at a specific altitude, or to ascend at a particular rate.
Predictions had already been run to work out where the payloads would land, again using the superb online software on habhub.org. Our biggest concern was the wind, which looked likely to make the payloads land in the North Sea. On the day, while it was breezy, the wind had abated enough for us to launch and expect our payloads to come down on the dry side of the Norfolk coast.
Balloons were inflated, the tracking software was tested again and then the first balloon was released (after a short pause to enable a Spitfire to reach Duxford unmolested – wimps). Some team members started to leg it to the chase cars, while the remainder made their way back to Pi Towers to monitor the data flow and go “oooh” and “ahh” as each fantastic image made its way back to Earth.
“Our bee survived to tell the tale, as did Lego’s Darth Vader and many others. It had been a phenomenal success.”
One payload ended up in the sea, the rest were recovered. This was the first time so many balloons had been launched at the same time and it generated a great deal of excitement in the HAB community. The day ended with the payloads opened up and various space persons were extracted from inside. Our bee survived to tell the tale, as did Lego’s Darth Vader and many others. It had been a phenomenal success.
The really brilliant thing about all this, though, is not the balloons, not the Raspberry Pi, not the add-on boards, not even the photos. It’s the people. The people who made it possible. The people who took part. The Raspberry Pi community as a whole and the Raspberry Pi Foundation especially.
Tim Peake, the first official UK astronaut, will take the Raspberry Pi higher than it’s ever been, and the brilliant thing is that we’ll all be able to share in the experience, all be able to learn from it. Fly safe Tim, but above all, have fun! He’ll be in space with a Raspberry Pi – how could he not have fun?
If you’re stuck on Earth like the rest of us, find a local Raspberry Jam and go there. Free your inner geek. You know you want to.
I would like to finish by thanking the Raspberry Pi Foundation for letting me anywhere near Pi Towers in the first place, and my school (Stoke College, Suffolk) in wholeheartedly embracing the Raspberry Pi. This enabled me to send five very excited pupils home last night with five of my Pis and the first five CamJam EduKit 3 Robotics Kits that had just arrived from PiHut. I didn’t give them any instructions, just asked them to build me a robot. I can’t wait to see what arrives.