Sub-systems for small satellites: so simple a teen can build them

03 Sep, 2019

We like to say that our goal is simplifying satellite technology and making it accessible, but is it so easy that even a teenager could build one? Thanks to a bold seventeen-year-old, we know that the answer is yes (mostly).

With the help of the Open Cosmos beeKit small-sat frame and his homemade 3D printer, A-level student Joe Iddon built his own Attitude Determination and Control System, a mechanism meant to change the orientation of a satellite once it’s in orbit. It’s made of both new and old parts, some salvaged from drones, school supplies, and Arduino boards he bought in bulk. Overall he achieved the project having spent roughly £20 on the whole thing. While not every teen will have access to their own 3D printer and the various bits and bobs needed to build satellite components, from scratch the parts would still cost less than £50.

Joe’s DIY Attitude Determination and Control System is controlled by light, moving itself to always face a light source. Joe demonstrated this with both a mini torch and a phone torch. In space this would allow the satellite to position itself towards the sun at all times. The system contains what satellite engineers call a reaction wheel. A fast-spinning wheel, or in Joe’s case an old computer hard disk, accelerates or decelerates with the resulting change in angular momentum causing the system to rotate clockwise or anticlockwise. Satellites normally have three of these reaction wheels on board to be able to rotate the satellite around all of its three main axes, allowing it to point its instruments in any possible direction.

Tech Talk

Joe’s instrument uses two Light Dependent Resistors (LDRs), that are used as the input to a Proportional Integral Derivative (PID) control system that uses the LDR’s relative intensities to provide an error function. This feedback loop then modulates the pulsing of the electric motor coils of the reaction wheel via three transistors (MOSFETs) which determines the speed of the wheel, which then changes the attitude of the satellite.

Last year Reading School took their computer science students to the Festival of Digital Disruption, where Joe approached our Customer Success Lead Dani Sors after the Open Cosmos presentation. Leaving with his business card, Joe was keen to be involved and wrote Dani asking how and sent links to projects he was already working on. Impressed by Joe’s initiative and talent, Dani challenged him to build his own Attitude Determination and Control System. The components would be easy and affordable to source and luckily Joe had a spare hard drive to use for it. Dani invited Joe to visit Open Cosmos after seeing the first stage of his functional ADCS. At that point his reaction wheel hung by a piece of string, so we provided him with a space-ready beeKit frame. With this, he could test his system inside a proper satellite body.

Joe came back a few weeks later with his completed project, now secured inside the satellite frame. He machined new 3D printed components, to make the system fit the beeKit. Parts like the resistor used to cost pounds but today they can be found for mere pence, and the overall affordability of supplies is improving. 

Open Cosmos is no stranger to using ‘off the shelf’ parts, some components coming from automotive industries which are already put through strict validation protocols. We then only take a few more validation test steps to qualify these parts for use in space. This saves both time and money, proving that space doesn’t have to be complex or expensive.

For Open Cosmos this project is the perfect proof that space is no longer the exclusive domain of governments with big pockets and dozens of rocket scientists. Space technology is within easy reach of anyone, being simpler, cheaper and more easily available. Where ADCS systems used to be complex and large, Joe’s project proves that these subsystems can now be built much cheaper and with only basic knowledge of programming simple mini computers like Arduino.

Open Cosmos will use Joe’s ADCS for demonstration purposes to other school kids, university students, and indeed our satellite customers. It is a great instrument to explain the principle of satellite subsystems and how standard components make space technology accessible to anyone.

While Joe may not yet know what he wants to do in the future, he is thinking about studying physics or natural sciences at university. In the meantime, you can find him on GitHub where he posts about his other cool projects such as a robotic arm that plays chess and a quadrupod inspired by the the walking movements of newts.