Upload
duongmien
View
213
Download
0
Embed Size (px)
Citation preview
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
EO
RG
E B
ER
NA
RD
/N
HP
A
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.
UPFRONT