A competition for space-bound students resulted in a tiny, can-sized, Raspberry Pi-powered satellite. Rob Zwetsloot boldly takes a look at it.

What would you do if you had to create a satellite the size of a drinks can? The yearly CanSat competition for students in their teens asks this question, and many teams have answered — including LittleBlueDot.

“The challenge for students is to fit all the major subsystems found in a satellite, such as power, sensors, and a communication system, into this minimal volume,” the team tell us. They came third in the country for their final build. As the competition instructions explain, “After building their CanSat, teams will be invited to launch events across the UK to launch their CanSats on small rockets, with their CanSats returning to Earth using a parachute designed by the students. Teams are set a primary mission of measuring air pressure and air temperature during the CanSat’s descent, with data being transmitted to the students’ ground station.”

They also needed to design a secondary mission, which in the case of LittleBlueDot included taking photos of the ground below to map it. “The idea of mapping large areas, including foreign bodies, came up when we were discussing potential asteroid mining in the future,” the team say. “And also improving efficiency in agriculture, both fields where large benefits could be seen from mapping land cheaply.”

Trial and error

For the project, Raspberry Pi was an obvious choice for the team — while a microcontroller would be able to handle the environmental recording and transmitting requirements, a Raspberry Pi computer allowed for on-board image processing. The team then got to work building and refining.

“Initially, a very basic CanSat was made to help visualise the size and space that was available to be worked with,” they explain. “Different ways to secure the Can’s inner electronics in an accessible way were explored. In V0, there were two bodies: a screw lid with an attached compartment behind, and the main module itself.”

The V1 build went from a vertical orientation to horizontal to accommodate a larger gap between the cameras. Across V1 and V2 builds, different ways of wiring up and loading the circuit were explored, and clear acrylic discs were added to protect the cameras from moisture and reduce their drag.

“In V1, the parachute was attached via four straight vertical holes,” the team continue. “V2 featured a more reliable solution, using four M5 nuts inset into the walls of the Can to secure the paracord in place and put the strain on the parachute rather than on the Can itself.”

After some issues at the regional launch, a V3 was created to better fit all the components they required.

“The Can was simplified by removing the inner module and trays [for the electronics], and a friction fit was used to directly mount components to the inside of the CanSat,” the team say. “During testing of the temperature readings, it was found that heat from the internal components was affecting the readings being taken. To mitigate this, fans were added for cooling, and vents were installed on both sides of the CanSat using a honeycomb grid to allow air flow. The strength of the vents were tested in Fusion 360 and they still passed the stress tests.”

With this, they were ready for the national launch, where they were part of the national finals.

Mapping with data

As well as cameras, the CanSat had temperature and pressure sensors, an IMU (inertial measurement unit), a magnetometer, and GPS. These were used to calculate altitude and orientation.

“The two on-board cameras took photos of the ground simultaneously,” the team explain. “This meant that an FFT [fast Fourier transform] taken of an image from the first camera would give a wave that was a translation of the wave an FFT would give for the second camera. This translation would vary based on the orientation of the Can, the distance between the two cameras, the altitude of the Can, and finally the actual altitude of points on the ground. Given values for the first three variables, the fourth could be calculated using trigonometry.”

The team came third overall in the competition. And the data? Sadly, due to a safety quick-release switch being released during launch, they were only able to get one set of images. Hopefully they can get it all working for another launch.

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A very rewarding thing about designing affordable hardware is watching young makers grow up with it, sometimes taking their interest in computing to university and beyond. We’ve seen kids who began playing around with Raspberry Pi go on to use our devices in their professional lives — in fact, that’s how a couple of our own engineers started out. In issue 149 of The MagPi, we spoke to the three siblings behind the GurgleApps YouTube channel. They’ve been sharing STEM projects for ten years now.

We’ve been covering projects from the team of siblings who make up GurgleApps for a long time — most recently their Colour Word Clock (image below) — and they themselves have been using a Raspberry Pi since the year it came out. In fact, it helped turn them into the makers they are today.

“Making became a part of our lives largely due to the influence of our parents, who filled our home with electronics, science, and coding projects,” the GurgleApps trio tell us. “Funnily enough, we weren’t hooked immediately — we had all this amazing equipment and knowledge at home, but took it for granted. The real spark came when Caleb received his first Raspberry Pi in 2012. Our dad playfully ‘forgot’ to tell us about the startx command, so we spent the first month working solely in the terminal, using simple commands like top and programming in Vi (a text editor) to create quiz and adventure games — without realising there was a graphical interface! It was rather frustrating for us at the time, but as our dad reminded us, it was nothing compared to his old ZX Spectrum.”

How did you start making videos together?

We started making videos together somewhat accidentally in 2015. It all kicked off with a prank on our dad where we used a Raspberry Pi to SSH into his computer and close the app he was working on. Amélie demonstrated the prank using simple shell commands, while Caleb handled the filming. Since we were too young for social media, we posted the video on our parents’ account. Unexpectedly, it went viral, gathering 1.4 million views! The overwhelming support inspired us to create more content, leading to the birth of our channel, GurgleApps.

During the COVID-19 pandemic, we noticed that many students — including us — were missing out on hands-on science experiments. We started recreating school physics experiments at home and sharing tutorials on our channel. This allowed others to keep learning and exploring STEM subjects despite the circumstances. We’re dedicated to making STEM education accessible and fun for everyone.

What was your first group maker project?

Our first significant group project was creating the Pico Piano (watch below). We built it using a Raspberry Pi Pico microcontroller and designed our own circuit board right at home. To make the circuit board, we used a DIY method: drawing the circuit design on a copper board with Sharpies and then etching it using ferric chloride. This hands-on process was both challenging and exciting, as it combined electronics, coding, and a bit of chemistry.

How has the channel affected your lives?

Running our YouTube channel has taught us a wide range of skills — from presenting and video editing to live-streaming and valuable maker and business skills. Live streaming helped us handle mistakes on the fly and build confidence. We’ve also been guests on podcasts and other live streams, which allowed us to meet lots of fun and interesting people in the maker community.

Our STEM knowledge has deepened significantly. Supportive viewers often share their expertise; for example, one viewer spent hours teaching us about PCB manufacturing, and another pointed out an inaccuracy in our light gate calculations, helping us learn and improve.

What’s your favourite thing you’ve made together?

Our favourite project we’ve made together is definitely the Word Clock! It’s special to us because it was inspired by our very first word clock project with a tiny 8×8 display over ten years ago. We’ve evolved it into a kit that you can now buy, and we’ve made everything open source — even the 3D print files for the case are available. We spent months perfecting it and putting everything we’ve learned into making it something we’re really proud of. What’s even more exciting is seeing people hack it to do things we never dreamed of. Watching others take our creation, build upon it, and share their own versions has been incredibly rewarding. We’ve recently updated our custom-made RGB LED matrix display — a key component of our word clock — and hopefully it will be ready for purchase from our shop very soon!

To see more of the trio’s projects and tutorials, subscribe to GurgleApps on YouTube.

The MagPi #150 out NOW!

You can grab the latest issue right now from Tesco, Sainsbury’s, Asda, WHSmith, and other newsagents, including the Raspberry Pi Store in Cambridge. It’s also available at our online store, which ships around the world. You can also get it via our app on Android or iOS.

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