Column One: Mir gets a lead so it can go walkies in space

Column One
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The Independent Online
IT HAS survived collisions, blow-outs, fire and computer failure. Now the Russian Mir space station faces the prospect of being hung in its orbit by a single copper thread.

A group of space engineers has applied for permission to attach a "space tether", seven miles long but less than half-an-inch thick, to Mir. In theory, this would prevent it from plunging to Earth sometime next year and keep it in orbit as a privatised alternative to the International Space Station (ISS).

The plan is not as crazy as it seems. Space tethers are well-established in theory but have not been fully tested. By pumping an electric current through the tether, the scientists hope to boost Mir's orbit without the enormous cost of launching a fresh fuel supply.

A private consortium of space engineers and venture capitalists has applied for an export licence from the US so the tether can be launched by Russian rockets early next year. "Mir is not pretty and new, but it's functional. So having this facility available makes sense," said Joe Carroll, head of Tether Applications in San Diego, one of the companies involved in the scheme.Chances of receiving the export licences were good, he said.

Although Mir is 13 years old and has suffered just about every mishap that can happen in space, the group of Americans and Russians believe its continued survival could be commercially viable. They have struck a deal with Energia, the Russian space agency, and formed a company called MirCorp to renovate and operate Mir as an alternative to the ISS.

However, time is running out. As Mir glances through the Earth's upper atmosphere, its orbit gets lower each day. A decision has be made soon on whether to bring Mir down in a controlled descent or to boost it higher in order to free it of the Earth's atmospheric drag.

If the plan goes ahead, Russian cosmonauts will attach the tether during a space walk so that Mir's solar panels can energise the copper wire with electricity, with the Earth's electrically charged ionosphere completing the circuit.

The tether will be travelling through the Earth's magnetic field at thousands of miles per hour and so its current will generate an electromagnetic force that will slowly accelerate the spacecraft and gradually lift it into a higher orbit.

"Basically, the electromagnetic tether acts as a very unusual electric motor. It's exactly the same principle worked out by Michael Faraday in 1831," Dr Carroll said. The project also has the support of Arthur C Clarke, the science-fiction author and space guru, who was one of the first people to propose the practical uses of cosmic tethers.

Nasa has also put its weight behind the concept of space tethers, saying it offers the prospect of "propellant-free propulsion" that will reduce the cost of placing and keeping satellites in orbit. "When properly controlled, the forces generated by this electrodynamic tether can be used to pull or push a spacecraft to act as a brake or a booster," said a Nasa spokesman.

Leading article, Review, page 3

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