SPORTS arenas of the future could be protected by water cannons鈥攏ot to
control rampaging fans, but to deflect lightning strikes. In June, a group of
American engineers plan to fire supersonic jets of salty water towards storm
clouds in a bid to trigger lightning. If it works, they say their system could
ultimately be used to protect people and property from lightning strikes.
The National Severe Storms Laboratory in Norman, Oklahoma, says lightning
hits around 600 people each year in the US鈥攌illing 100. The majority of
victims are in sports grounds or playgrounds when struck. The strikes lead to
insurance claims of an astonishing $5 billion per annum. So predicting
when and where lightning is going to strike is crucial鈥攅specially if
you鈥檙e in the business of launching fuel-laden spacecraft. In the 1960s,
scientists working for NASA used large firework-like rockets to trail earthed
copper wire into storm clouds near Florida鈥檚 Kennedy Space Center, and succeeded
in attracting lightning bolts. But the idea was ruled out as too dangerous to
try near spacecraft. And you certainly couldn鈥檛 have spent rockets landing on
crowds at open-air concerts or sports fields, either.
Now Doug Palmer, founder of a company called BoltBlocker in San Diego,
California, reckons lightning could be drawn to a safe spot by squirting an
ultra-thin jet of water鈥攎ixed with salt and soluble polymers鈥攖owards
the storm cloud. The salt boosts the water鈥檚 conductivity while the long-chain
polymers help prevent the jet breaking apart into a stream of droplets. Palmer鈥檚
idea is to propel a jet with a diameter of just 1 centimetre around 300 metres
into the air. His idea is that any lightning about to form will be attracted
towards the conducting water jet. When the strike is triggered, the 10,000-amp
current will pass down the jet, hopefully safely earthing itself on a hefty
copper cone surrounding the water nozzle.
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While it sounds on the frontiers of feasibility, Palmer鈥檚 idea might just
work, says Charles Moore, an atmospheric physicist at the New Mexico Institute
of Mining and Technology in Socorro. The US Navy accidentally demonstrated a
similar effect in the 1960s, he says. Detonating an experimental depth charge
sent an enormous plume of salty seawater into the sky鈥攊nducing a lightning
strike from nearby storm clouds.
To protect places like sports stadiums from strikes, Palmer says you could
set up mobile water cannons around the perimeter. Detectors rigged to the
cannons would sense when the electric fields were high enough to make lightning
strikes probable. The water jet would then be fired to act as a temporary
lightning conductor.