NewScientist.com news service - Max-Born-Berufskolleg

Space elevators to heave themselves skyward
20:07 16 October 2006
NewScientist.com news service
Kelly Young
Enlarge image
A crane-mounted ‘racetrack’ was used for NASA's 2005 climber competition (Image: Spaceward Foundation)
A few early prototypes for space elevators will try to get off the ground at a competition at the Wirefly X
Prize Cup in Las Cruces, New Mexico, US, on 20 and 21 October.
The hope is that one day a space elevator, comprised of a robot that will climb a strong tether about
100,000 kilometres (60,000 miles) long, will be able to send humans or other cargo cheaply into space.
To spur the development of that technology, NASA set up two annual competitions, called the Power
Beaming and Tether Challenges. The first competitions were held in 2005 – but no one won either of
them (see Space elevators stuck on the first floor).
In the Beam Power Challenge, teams have to send a robotic climber up a crane-mounted tether at a
minimum speed of one metre per second. The climbers will be judged by their speed and weight, with
the top three teams taking home $150,000, $40,000 and $10,000, respectively.
The catch is they cannot be powered by fuel, batteries or an electrical extension cord because a real
space elevator could not carry these things on a trip into space. So the robotic climbers must use solar
arrays powered by light sent from the Sun, solar reflectors, a spotlight, lasers or microwaves.
A dozen teams will compete in the climber challenge. About six to eight teams may have hardware that
could climb all the way to the top, says Ben Shelef, co-founder of the Spaceward Foundation, a space
advocacy group in Mountain View, California, US, which administers the competition. Two to three of
those could nab the prize money.
Laser source
New scientist from 16. october 2006

In 2005, teams had to use a spotlight that was provided for the competition. This year, they can bring
their power source.
A Canadian team from the University of Saskatchewan, which climbed to a record 12 metres (40 feet)
in last year's competition, says it is developing a laser power source for its climber.
The laser will probably not be ready in time for the competition, so the team will rely on a powerful
search light instead. The spotlight may be cheaper in the short term, but in the long term, using energy
beamed from a laser may be a more efficient way to move a space elevator, it says.
If they had been able to use a laser this year, they had planned to climb 61 metres (200 feet), to the top
of the tether. Now, they believe they may only reach half that height. "We're kind of thinking we might
not be ready this year," says team president Clayton Ruszkowski. "I'm hoping for 100 feet."
Steve Jones, captain of a team from the University of British Columbia in Canada, says his team's
climber is light enough that it does not need a concentrated beam source, like a laser. Instead, it can
run on either the Sun or a spotlight.
"We're pretty sure we can win with either," Jones told New Scientist. Indeed, his team was voted most
likely to win in 2006.
Breaking point
The related Tether Challenge aims to spark the development of lightweight materials strong enough to
stretch 100,000 kilometres into space without breaking. Space elevator proponents believe a thin rope
of carbon nanotubes will ultimately be needed for the task.
For the challenge, 2-metre-long tethers are wrapped in loops and stretched to the breaking point. The
tether cannot weigh more than 2 grams and must carry 50% more weight before breaking than the best
tether from the previous year.
Three teams will test their tethers' strength this year, including a group from the University of British
Columbia. This year, they are using a tether made of Zylon fibres, which were once used in bulletproof
vests. To maximise the material's strength, the team experimented with fabrication methods such as
whether to tie the ends of the fibres or loop them.
The competitions will be held annually until 2010, so even if no one wins them this year, either, the
competitors can try again: "We're definitely just going to keep going and see what we can do for next
year," Jones says.
New scientist from 16. october 2006