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If you've seen Gravity you'll know what an out-of-control cloud of space debris travelling
at thousands of miles an hour can do to a Hollywood actor.
And our presence in orbit. Also that. But whilst the film may have been a work of fiction,
the basic premise, of a chain reaction of satellite destruction in which debris from
one spacecraft hits and destroys another, creating more debris and destroying more craft,
is a very real possibility.
It's called the Kessler Syndrome, and many scientists reckon it's only a matter of time
before it happens - there are hundreds of thousands of potentially deadly pieces of
debris whipping round our planet within satellite orbits, which themselves are close to capacity.
And now a group of students at Britain's Leicester University have identified the satellite they
believe could kick start the whole process. It's called Envisat. It weights 3.1 tonnes,
orbits at 490 miles above the Earth, and as of April 2012, it's been dead and tumbling
out of control. Envisat is already a problem - it's passed within 200 metres of other objects
twice since it shut down, and another spacecraft has already had to steer out of its path.
And it'll be up there causing trouble for 150 years before re-entering the atmosphere.
Envisat is just the most pressing problem though, in the coming decades hundreds of
large satellites will join it in spinning aimlessly around in space. One of them is
almost certain to eventually collide with something, potentially propelling Earth back
to the 1950s.
The Leicester students are proposing using Nasa's Robotic Refuelling Mission, a satellite
repairing and refuelling craft currently in early testing, to slow dangerous satellites
and steer them in towards the Earth, one of several solutions currently being mooted for
the inevitable task of clearing up our cluttered cosmos.