6 | NewScientist | 14 November 2009

TODAY a cable dangling beneath a helicopter, tomorrow a climb to the stars. The far-out idea of space elevators has been brought a step closer by a robot whose climbing prowess has bagged its makers a previously unclaimed NASA prize .

To build a space elevator, one end of a cable thousands of kilometres long would be anchored on or near the equator, while the far end is deployed in space. Robots climbing the cable should provide a cheap route into space, the scheme’s advocates say, but huge technological hurdles remain.

One of the most pressing of these is finding a way to supply power to the robot. So in 2005 NASA inaugurated the Power

Beaming Challenge, an annual competition in which robotic climbers, powered wirelessly from the ground, attempt to ascend a cable. Prize money

NASA’s rope trick totalling $2 million has been on offer for successful challengers.

Now a robotic climber built by a team called LaserMotive, based in Seattle, Washington has won $900,000 for a 900-metre climb up a cable suspended from a helicopter hovering above Edwards Air Force Base in Mojave, California. The climber took its power from on-board photovoltaic cells that absorb energy from a ground-based infrared laser.

On 4 November, LaserMotive’s robot completed the climb in 4 minutes, an average climb rate of about 3.7 metres per second. The following day it did slightly better, climbing at 3.9 metres per second. Two other climbers stalled during their attempts and were unable to continue. NASA is holding the remaining prize money in reserve for climbs faster than 5 metres per second.

Though a space elevator is only a distant prospect, NASA is interested in wireless power transmission for other applications, such as beaming power to lunar rovers travelling in shadowed craters where no solar energy is available.

At last, it works

GENE therapy is coming in from the cold. Two boys treated three years ago with a gene therapy for X-linked ALD, the brain disease featured in the film Lorenzo’s oil, fared so well that doctors have treated a third and are now looking for adult volunteers.

“They have normal, family lives,” says Nathalie Cartier of the Descartes University in Paris, France, a member of the team that pioneered the ALD gene therapy.

ALD is caused by a faulty gene

that prompts the myelin sheath coating nerves in the brain to wear away, causing impaired speech, movement and eventually death.

Cartier and her colleagues took blood stem cells from two 7-year-old boys with ALD, infected the cells with a virus carrying a correct copy of the defective gene, then re-injected the stem cells. The boys’ symptoms stabilised within 14 months and have not worsened since (Science, DOI: 10.1126/science.1171242).

Early gene therapy trials were stopped after triggering cancer .

–Better than tropical trees–

Northern forests are cool CHAMPIONS of carbon offsetting may

have been barking up the wrong tree.

It is generally assumed that the tropics

are the best place to plant forests in

order to sequester carbon and cool

the planet, but a study of the effects

of tree planting is casting doubt on

this idea. To maximise climate benefits

we should be planting trees at higher

latitudes, the study suggests.

Alvaro Montenegro at the

University of Victoria in British

Columbia, Canada, and colleagues

used high-resolution satellite data

to work out where new forests would

bring the biggest benefit. They

estimated the net climate impact of

planting trees on 5-kilometre-square

plots of cropland in locations where

forests can be expected to thrive.

Their calculations took into

account both the cooling effect of the

trees soaking up CO2 and the heating

effect which would result from the

trees reflecting less sunlight than the

crops they replaced. To their surprise,

Montenegro’s team found that on

balance, planting forests in northern

Russia, central Canada and Europe

would cool the climate more

effectively than planting them in

India, Brazil and most of China (Global

and Planetary Change, DOI: 10.1016/j.

gloplacha.2009.08.005).

Govindasamy Bala at the Indian

Institute of Science in Bangalore

reckons existing tropical carbon-

offsetting schemes may still have the

edge, however. Montenegro’s study

may have overestimated the amount

of carbon forests in Siberia and

Canada can store, he warns.

“One of the most pressing technological hurdles is finding a way to supply power to the robot”

WHAT’S causing spacecraft to

mysteriously accelerate? The Rosetta

comet-chaser’s fly-by of Earth on 13

November may provide the answer.

The anomaly emerged in 1990,

when NASA’s Galileo spacecraft

whizzed by Earth to get a boost

from our planet’s gravity and gained

4 millimetres per second more than

expected. Other probes experienced

the same effect, leading some to

suggest that Einstein’s theory of

gravity needs modifying to explain it.

Fly-by may solve speed anomalyG

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All eyes are now on Rosetta,

which is set to swing by Earth

again this week. If it gains an extra

1.1 millimetres per second relative to

Earth, it would vindicate a formula

that reproduces the anomalies seen

so far. The formula, published in

2008 by ex-NASA scientist John

Anderson and his team , hints that

Earth’s rotation may be distorting

space-time more than expected and

thus influencing nearby spacecraft,

though no one can explain how.

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