----- Original Message -----
Sent: Saturday, September 13, 2003 12:57
PM
Subject: The cheap way to the stars - by
elevator
The cheap way to the stars - by escalator
David Adam, science correspondent
Friday September 12 2003
The Guardian
If climbing a stairway to heaven sounds like too
much hard work, then a conference of 70 scientists and engineers opening in
Santa Fe today may offer hope of a more leisurely way into space.
In
two days of discussions, the scientists aim to turn into a reality an ambition
that has been around for at least a century: the creation of a space elevator
that would deliver satellites, spacecraft and even people thousands of
kilometres into space along a vertical track.
Engineers say that
recent advances in materials science - particularly in the development of
carbon nanotubes - mean that such a system, which first gained widespread
attention when the science fiction writer Arthur C Clarke described it in his
1979 novel Fountains of Paradise, is no longer pure science fiction.
Mr Clarke - who once said a space elevator would only be built "about
50 years after everyone stops laughing" - was due to address the scientists at
the Santa Fe conference today by satellite link from his home in Sri
Lanka.
The American space agency Nasa is no longer laughing. It
is putting several million dollars into the project under its advanced
concepts programme.
At the heart of a space elevator would be a
cable reaching up as far as 100,000km from the surface of the Earth. The
earthbound end would be tethered to a base station, probably somewhere in the
middle of the Pacific ocean. The other end would be attached to an orbiting
object in space acting as a counterweight, the momentum of which would keep
the cable taut and allow vehicles to climb up and down it.
A
space elevator would make rockets redundant by granting cheaper access to
space. At about a third of the way along the cable - 36,000km from Earth -
objects take a year to complete a full orbit. If the cable's centre of gravity
remained at this height, the cable would remain vertical, as satellites placed
at this height are geostationary, effectively hovering over the same spot on
the ground.
To build a space elevator such a geostationary
satellite would be placed into orbit carrying the coiled-up cable. One
weighted end of the cable would then be dropped back towards Earth, while the
other would be unreeled off into space. Mechanical lifters could then climb up
the cable from the ground, ferrying up satellites, space probes and eventually
tourists.
The biggest technical obstacle is finding a material
strong but light enough to make the cable; this is where the carbon nanotubes
come in. These are microscopically thin tubes of carbon that are as strong as
diamonds but flexible enough to turn into fibre. In theory, a nanotube ribbon
about one metre wide and as thin as paper could support a space
elevator.
No scientist has yet succeeded in making such a fibre,
but Rodney Andrews, a carbon nanotube expert from the University of Kentucky
will tell the conference: "Until some of the basic science concerning how to
connect nanotubes together and transfer load between them in a composite is
understood it will remain elusive, but a lot of progress is being made."
Brad Edwards, a space scientist who has been developing the space
elevator concept for several years, said there was still a lot of scepticism
to overcome. "Initially, people look at me like they're trying to work out
whether or not I'm pulling their leg," he said.
Dr Edwards says
the original satellite used to send up the cable should provide enough tension
in the cable for the first vehicles to climb into space, each of which would
then be added in turn to the counterweight. These lifters would clamp
caterpillar tracks to either side of the cable and would be powered by
converting laser light beamed up from the ground into electricity.
"None of it is really extravagant," said Dr Edwards, who estimates it
would take about $7bn (£4.4bn) to turn the concept into reality. He
hopes to have a final elevator design hammered out by next year.
He said the floating base platform would be placed hundreds of miles
from aircraft routes and shipping lanes and would be in a region of the sea
where storms, lightning and high waves are rare.
The biggest
hazard could be space junk, but Dr Edwards said the floating platform would be
moved around to steer the cable out of the way. He says it would slash the
price of access to space 400-fold, and could allow cheaper, faster travel to
other planets.
One unlikely problem could be capturing the
public's imagination. "When we actually start launching this it's going to be
kind of boring," Dr Edwards said. "There's no smoke, there's no pillars of
fire and there's no loud rumbling noises. There's just this thing that slowly
ascends the ribbon into space."
