In just under two years, 50 spacecraft will purposefully destroy themselves in the Earth’s atmosphere, and a South African team is helping them do it.
Nanosatellites – also known as cube satellites or “CubeSats” – are small in the world of satellites, but are gaining traction globally as a comparatively cheap way to get a foot in the space-race door. These tiny satellites are 10cm cubes, weighing no more than 1.3kg, and can be stacked together to create larger satellites.
Robert van Zyl, director of satellite engineering systems at the Cape Peninsula University of Technology, says: “Since 2000, more than 300 CubeSats have been launched … It is expected that 3 000 nano- and microsatellites will be launched over the next five years. The cost of a big satellite can run into hundreds of millions of dollars, whereas a CubeSat can be built for about $100 000 and launched for much the same, depending on the complexity of the mission.
“For this reason, Cube-Sats were initially used to train students for the aerospace industry. But now these small spacecraft can be used to track and trace aircraft and vessels at sea,” he says. South Africa, through the university’s French South African Institute of Technology, launched its first CubeSat, TshepisoSat, in 2013.
Built, launched and annihilated
As part of the European Commission-funded QB50 project to facilitate access to space, 50 CubeSats will be built, launched and annihilated. The mission brings together 27 countries from around the world, including South Africa, to co-ordinate the launch of CubeSats for space research. A Stellenbosch University spin-off company, CubeSpace, will be building control systems for some of the satellites.
“They will be launched in early 2017 into an orbit below the International Space Station,” says Professor Herman Steyn, head of satellite engineering in the electronic engineering department at Stellenbosch University. The nanosatellites will be equipped with sensors that will “measure all the essential elements in the lower part of the ionosphere, [the charged upper part] of our atmosphere”, Steyn says.
“[This allows researchers] to get better models for satellites when they re-enter and burn out in the atmosphere. You can predict, if any parts of the satellite are left, where they will fall to Earth,” he says.
This is becoming an increasingly important research question because, in order to acquire a licence to put a satellite into space, the object has to destroy itself or fall out of orbit within 25 years – and people need to know where this debris will land if it survives the atmosphere in its fall back to Earth.
This necessity is driven by the sheer quantity of “space junk” – objects the size of a marble, or bigger, that orbit the planet.
“More than 500 000 pieces of debris, or space junk, are tracked as they orbit the Earth,” according to Nasa. They travel at speeds of up to 28 000km/h, which means they could travel the length of the African continent in less than 20 minutes, “fast enough for a relatively small piece of orbital debris to damage a satellite or a spacecraft”, the space agency says.
The rising population of space debris increases the potential danger to all space vehicles, but especially to the International Space Station, space shuttles and other spacecraft with humans aboard, Nasa says.
Steyn says the danger is that every time there is a collision, more space junk is created. “If there are more collisions due to previous collisions, it could make it impossible to make use of satellites and space for communications,” he says.
However, for CubeSpace, the QB50 project offers an opportunity to build the country’s capacity in space technologies. The company, which was spun out of Steyn’s research group at Stellenbosch University, will be building the control systems for some of the CubeSats.
“Up to now, most CubeSats have been uncontrolled, randomly tumbling in orbit,” Steyn says. “It makes it difficult to orientate your antennas to a ground station, a solar panel to the sun or a camera to Earth. There are not many companies, fortunately for us, that supply control systems for CubeSats.”
Mike-Alec Kearney, cofounder of CubeSpace and a graduate of Steyn’s research group, says the control boards use sensors to determine the CubeSats’ orientation in relation to the Earth and the sun. The boards then use magnetic torquers, a collection of wires conducting electricity that creates magnetic fields, to control the way that satellites spin.
The company, in conjunction with Stellenbosch University, will supply control units for 15 satellites that will be launched as part of the QB50 initiative. It will also supply its own CubeSat, ZA-AeroSat, to the project, he says.
High-tech manufacturing niche
This has exciting consequences for South Africa’s small space industry. Satellite production has been touted by the science and technology department, as well as the trade and industry department, as a high-technology manufacturing niche that South Africa could exploit.
However, the industry has not been particularly kind to our homegrown satellite companies. The best-known example is SunSpace, which was started by a group of Stellenbosch University graduates. Although the company was responsible for South Africa’s pathfinder satellite, Sumbandila, it did not have enough contracts to sustain its business.
This is where experts believe that CubeSats offer a different avenue for research and industry. “CubeSats are winning over the youth to the space sector,” says Van Zyl. “By being cheaper to build and launch into space, they provide a cost-effective platform for training and research, especially for countries where a heavy investment in a space industry has to be weighed against more immediate needs such as health and welfare.”
Steyn, who was involved in SunSpace, says: “Stellenbosch University … [is] helping us to establish the company [CubeSpace]. I still have a couple years left as a lecturer [before my retirement], I’m now also in this company with the engineers.”
They use the research output the university unit develops “to come up with new sensors and actuators … controlling a satellite’s attitude”, he says. “We want to be ahead of the rest of the world, so that our parts are always wanted. We want to stay unique in what we are doing.”