Tuesday, October 17, 2006

Space elevators to heave themselves skyward

20:07 16 October 2006
NewScientist.com news service
Kelly Young

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 1 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

In 2005, teams had to use a spotlight that was provided for the competition. This year, they can bring their own 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," admits 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.

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.