The Raspberry Pi has been enthusiastically picked up by a dedicated modding community, and the cheap Linux computer has been used in projects ranging from drones to speech-controlled robots. Now its creators want to take Raspberry Pi to a new frontier: space.
The credit card-sized, ARM-based computers could easily be integrated into satellites, according to the device's designer, Eben Upton, who envisages them also being used for research in test rockets and high-altitude balloons.
Upton, a space fan since he was a child, sees a role for Raspberry Pi in sounding rockets, which are used in astronomy, aeronomy and microgravity research. These rockets are launched a couple of hundred of kilometres into space, stay there for a few minutes, then fall back to Earth; they carry scientific equipment to take measurements during the journey.
Upton believes the Raspberry Pi could be used as a lightweight device for controlling the avionics in such sub-orbital rockets; for example, it could designate the direction, navigation and thrust.
With avionics there is a need to react very fast, he said. "Often [with] avionics platforms, there are hard real-time constraints," said Upton. "You get a signal from a sensor, from a gyro, and you run some actuator in order to correct, so if the rocket starts to go left, you want to bend it right a little bit. You want to do that over very short time scales."
In addition, one advantage of the Raspberry Pi is that it connects easily to a video camera, he noted. This means it could be used as a programmable platform for imaging — recording video — during a suborbital shot.
Real-time operating system
The device comes with a standard Debian Linux operating system, which may not be ideal for dealing with the speed of changes that need to be made in real-time rocket launches, Upton said. Rocket users may have to install a real-time operating system (RTOS), which could be Linux or proprietary.
However, there could be a conflict if the computer is being used for video recording.
"[An RTOS] potentially screws up the multimedia, because our multimedia set-up is very dependent on having Linux," Upton said. "There's a tension between those two."
"It could probably be resolved, but there's probably a chunk of engineering before you have a single chip which is doing both the engine control and taking pretty pictures as you're zooming around."
The Raspberry Pi chief noted that its use in rockets is still speculative; no one has done it yet, and established platforms already have lightweight avionics integrated. However, people building sounding rockets from scratch may be attracted to the sub-£30 computer for its open system design.
"You're not going to save that much by rolling up your Raspberry Pi with the rest of your avionics," Upton said. "But if you were doing a clean-slate design — if I was going to sit down today and build a sounding rocket — then I might well think about using a Raspberry Pi for a control system. Because it's there, and it's cheap, and I understand it."
Using Raspberry Pi for sounding rocket software design could be attractive because of the transparency of the open-source development process, too.
"You can understand what's running right down to the metal on the ARM side," said Upton. "There's no hidden stuff. You know what every instruction is doing.
"So if you need to know that your device is going to need some real-time constraint, you can know what's going on. You can know that lots of people looked at the code. Many eyes make bugs shallow — that's the phrase," he added.
Satellite of RasPi
More likely is that the Raspberry Pi will be used with satellites first. Upton has been talking to a team from the University of Leicester about putting the device's processing power to work with CubeSats, which are 10cm-cubed mini-satellites.
CubeSats, like the Raspberry Pi, tap into off-the-shelf components to put devices within reach of more people. As well as being a way to give undergraduates experience in building space-tolerant hardware, Upton sees the mini-satellites as having a role in educating kids and getting them enthusiastic about technology.
"This thing's in orbit. When it comes over you, you can upload a message onto it. Then somebody else somewhere around the world can downlink the messages off it," he said. "So it's got that kind of fun thing that kids like."
The Raspberry Pi's most likely role in CubeSats is "simply running the systems on the device", according to Upton.
"A CubeSat typically has got a bunch of solar cells and batteries and some radio hardware, maybe a heater to keep it warm in the Earth's shadow," he said. "There's a variety of bits and pieces of hardware in there, and you need some processing element to control those. Now, Raspberry Pi is a little bit overcooked for that. But once you've got it there, you could potentially think about doing imaging as well."
Beyond that, there could be a role for the device in ground stations. Upton also thinks people doing home-brew, ham radio-like communications with satellites could use a Raspberry Pi to receive signals from satellites.
For organisations working with kids, though, the most achievable way to head into the atmosphere are high-altitude balloons, according to Upton. Schools could send up a balloon to take pictures of the curve of the Earth, he suggests.
"You can get to 10 to 20 kilometres up, which, functionally, from a lot of points of view, is space," he said. "From a child's point of view, it's got almost all of the cool stuff of being in space, with a millionth of the cost of actually going into orbit."
"I will eat my hat if we don't see Raspberry Pi-based high-altitude ballooning in the next year, because it's such an obvious science-fair project," he said.
Upton acknowledges that we have yet to see any space-based projects with Raspberry Pi. However, though the device only went on sale in February, people have already come up with a huge range of uses and projects for it — and the Raspberry Pi's multimedia capabilities could give it a boost.
"This is all incredibly speculative, because none of this has been done," Upton said. "The proof of the pudding will be when it's done, that's when we'll find out what people use it for. I suspect that the biggest asset with all of these on day one will be the fact that we can drive a camera."