Space, the low-tech frontier

For more than a century, the idea of space tethers—lines tying satellites to the ground or to each other—has been popular, if not a little impractical.

Proposed and demonstrated missions have so far required deployment of pre-attached tethers. Until now nobody has devised methods for attaching them in space, but Australian Chris Blanksby, PhD student at the Department of Aerospace Engineering at the Royal Melbourne Institute of Technology, has devised a 3D computer model to simulate the dynamics involved.

Blanksby’s control schemes are being developed to enable the tether to rendezvous with incoming payloads and release them into the appropriate trajectory.

‘If the tethers work, which they are expected to in maybe 10 to 20 years, then you could have launches for about one-hundredth the cost of what they are at the moment,’ said Blanksby. ‘You can use them for lots of applications, anything from electrodynamics – which involves using the earth’s magnetic field to generate power or thrust – to capturing other satellites and tossing them up into higher orbits, or retrieving space junk.’

Several basic experiments in orbit have established the feasibility of space tethers, the first of which was during the Gemini missions of the 1960s.

But Blanksby has never had the chance to test his complex calculations outside a virtual simulation using Maple and Mat Lab to determine the behaviour of the tether.

‘The intention was to make it very high-speed because eventually you need to use it on board a satellite and it has to be a lot faster than real time in order to predict ahead,’ said Blanksby.

Blanksby believes prototype systems could be operating within several years. ‘Maybe in eight years time we would like to see a demonstration mission, technology for controlling the nets capturing sub-satellites, and lifting up to a higher orbit a small system, maybe total mass 100-200 kilos. Then maybe another 10-15 years, possibly 20 years, beyond that, we could see a light scale approach capable of 50 payloads of up to 2-5 tons in total, various orbits.’

Interest in his tether simulation software has so far come from Japan, the United States and Holland.