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Striking Back at Lightning With Lasers
Seldom is the weather more dramatic than when thunderstorms strike. Their
electrical fury inflicts death or serious injury on around 500 people each year
in the United States alone. As the clouds roll in, a leisurely round of golf can
become a terrifying dice with death - out in the open, a lone golfer may be a
lightning bolt"s most inviting target. And there is damage to property too.
Lightning damage costs American power companies more than $100 million a
year.
But researchers in the United States and Japan are. planning to hit back.
Already in laboratory trials they have tested strategies for neutralising the
power of thunderstorms, and this winter they will brave real storms, equipped
with an armoury of lasers that they will be pointing towards the heavens to
discharge thunderclouds before lightning can strike.
The idea of forcing storm clouds to discharge their lightning on command is
not new. In the early 1960s, researchers tried firing rockets trailing wires
into thunderclouds to set up an easy discharge path for the huge electric
charges that these clouds generate. The technique survives to this day at a test
site in Florida run by the University of Florida, with support from the
Electrical Power Research Institute (EPRI), based in California. EPRI, which is
funded by power companies, is looking at ways to protect the United States"
power grid from lightning strikes. "We can cause the lightning to strike where
we want it to using rockets," says Ralph Bernstein, manager of lightning
projects at EPRI. The rocket site is providing precise measurements of lightning
voltages and allowing engineers to check how electrical equipment bears up.
Bad behaviour
But while rockets are fine for research, they cannot provide the protection
from lightning strikes that everyone is looking for. The rockets cost around
$1,200 each, can only be fired at a limited frequency and their failure rate is
about 40 per cent. And even when they do trigger lightning, things still do not
always go according to plan. "Lightning is not perfectly well behaved," says
Bernstein. "Occasionally, it will take a branch and go someplace it wasn"t
supposed to go."
And anyway, who would want to fire streams of rockets in a populated area ?
"What goes up must come down," points out Jean-Claude Diels of the University of
New Mexico. Diels is leading a project, which is backed by EPRI, to try to use
lasers to discharge lightning safely - and safety is a basic requirement since
no one wants to put themselves or their expensive equipment at risk. With around
$500,000 invested so far, a promising system is just emerging from the
laboratory.
The idea began some 20 years ago, when high-powered lasers were
revealing.their ability to extract electrons out of atoms and create ions. If a
laser could generate a line of ionisation in the air all the way up to a storm
cloud, this conducting path could be used to guide lightning to Earth, before
the electric field becomes strong enough to break down the air in an
uncontrollable surge. To stop the laser itself being struck, it would not be
pointed straight at the clouds. Instead it would be directed at a mirror, and
from there into the sky. The mirror would be protected by placing lightning
conductors close by. Ideally, the cloud-zapper (gun) would be cheap enough to be
installed around all key power installations, and portable enough to be taken to
international sporting events to beam up at brewing storm clouds.
A stumbling block
However, there is still a big stumbling block. The laser is no nifty
portable: it"s a monster that takes up a whole room. Diels is trying to cut down
the size and says that a laser around the size of a small table is in the
offing. He plans to test this more manageable system on live thunderclouds next
summer.
Bernstein says that Diels"s system is attracting lots of interest from the
power companies. But they have not yet come up with the $5 million that EPRI
says will be needed to develop a commercial system, by making the lasers yet
smaller and cheaper. "I cannot say I have money yet, but I"m working on it,"
says Bernstein. He reckons that the forthcoming field tests will be the turning
point - and he"s hoping for good news. Bernstein predicts "an avalanche of
interest and support" if all goes well. He expects to see cloud-zappers
eventually costing $50,000 to $100,000 each.
Other scientists could also benefit. With a lightning "switch" at their
fingertips, materials scientists could find out what happens when mighty
currents meet matter. Diels also hopes to see the birth of "interactive
meteorology" - not just forecasting the weather but controlling it. "If we could
discharge clouds, we might affect the weather," he says.
And perhaps, says Diels, we"ll be able to confront some other
meteorological menaces. "We think we could prevent hail by inducing lightning,"
he says. Thunder, the shock wave that comes from a lightning flash, is thought
to be the trigger for the torrential rain that is typical of storms. A laser
thunder factory could shake the moisture out of clouds, perhaps preventing the
formation of the giant hailstones that threaten crops. With luck, as the storm
clouds gather this winter, laser-toting researchers could, for the first time,
strike back.
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