Scottish engineers have developed a sail system that pulls small satellites out of orbit to avoid increasing the amount of space debris.
The technology, developed by Glasgow University and local firm Clyde Space, is designed to be installed as a module on satellites known as CubeSats and released when the craft reaches the end of its life in order to drag it back to Earth.
The system could enable CubeSat operators to put their craft into relatively high orbits from where they can take many years to naturally return to Earth and otherwise add to the substantial amount of old satellites and other space debris, creating an increasing hazard for operating craft.
Known as the Aerodynamic End Of Life Deorbit System (AEOLDOS), it comprises four thin membranes that are released via coiled struts that spring out from the craft to create sails with a total area of 3m2.
Glasgow University’s Dr Patrick Harkness, who designed AEOLDOS, told The Engineer that the technology was aimed at the CubeSat community, largely made up of students, academics and amateur enthusiasts.
‘You might want to look at the end-of-life disposal of your space craft because you’re dealing with requirements from your space agency, or you think it’s the right thing to do, or you want to fly in a slightly higher orbit and still meet the orbit requirements,’ he said.
The UN recommends that CubeSats stay in orbit no longer than 25 years, less than the time it takes for craft to return from higher orbits. But CubeSats at lower orbits can also remain in orbit far beyond the life of their mission and so add to the debris.
The main challenge for Harkness was simplifying the release mechanism as much as possible to reduce the chances of anything going wrong with it over the lifetime of the CubeSat’s mission, which would usually be up to around five years.
Each AEOLDOS device is made up of four cartridges, each containing a folded sail and a strut coiled around a central hub, which Harkness compared to a tape measure.
‘A tape measure will spring into a coil when you release it,’ he said. ‘We’ve turned that on its head so when you release the coil, the tape springs out.’
Each cartridge is designed to release its strut in the direction of the coil’s radius (rather than in a tangential direction of 90o to the radius).
‘That means each of the four sails in the cartridges are symmetrical,’ said Harkness. ‘That simplifies the fold pattern a lot and means you can use the modules interchangeably.
‘The hub is shaped like a flower instead of being round and that means that as the tape comes to the end of its deployment it has a soft stop rather than stopping suddenly.’
AEOLDOS has several different types of sail membrane for different purposes that can be installed as necessary, for example, a cheap version for ground testing and a reflective version that could be used for solar sailing.
Harkness has worked with Clyde Space to make the system compatible with the company’s CubeSats and hopes to make it commercially available by the end of 2012 following further development.
Surrey Space Centre is developing a similar technology in partnership with EADS Astrium. The researchers on this “CubeSail” project are conducting their final tests and are hoping for a first launch next year, according project leader Professor Vaios Lappas of Surrey University.