Static helps satellites swarm in formation
(New Scientist Via Thomson Dialog NewsEdge) STATIC electricity, the phenomenon that makes your hair stick to a woolly hat or a balloon cling to a wall, could be used to control satellites in space.
Groups of small satellites can perform like a single, much bigger craft. The European Space Agency's Darwin mission scheduled for 2015, for example, will combine four satellites to look for signs of extraterrestrial life. Telescopes on three of the craft will direct light to a central hub, to work like a single, much bigger telescope. Larger swarms could combine to function as giant communications antenna.
But maintaining or altering a swarm's formation consumes a lot of fuel. Now researchers at ESA have shown that static electricity can be used to make satellites attract and repel each other, allowing them to be controlled using much less fuel.
The charge could be generated using modified versions of conventional ion thrusters, which produce thrust by firing beams of positive ions. Normally these beams are neutralised with an electron gun after they leave the engine so that the craft's net charge stays the same. "By altering that feature we could purposely change a satellite's charge," says team leader Dario Izzo. And because only limited power less than 1 watt would be needed to generate a charge, the engine would use less fuel, saving weight.
The team simulated swarms of up to six satellites, which were made to change from a tetrahedron to a square formation with and without the electrostatic technique. They found that for four satellites flying in formation, spaced around 20 metres apart, the technique reduced fuel consumption by 98 per cent.
Satellites could be spaced further apart depending on their orbit, says Izzo. "In geostationary orbit it would be possible [to control the satellites] over around 200 metres," says Izzo. In interstellar space control would only extend about 20 metres as the electric field decays faster in space plasma.
Using the technique could make satellite swarms last longer, says Hanspeter Shaub, who researches spacecraft formation flying at Virginia Polytechnic Institute and State University in Blacksburg. "Fuel is a big problem because we want to maintain formation for years and years. Using electrostatic forces can solve it."
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