CAPE CANAVERAL, Fla. – The lightning that thwarted today's
planned launch of the space shuttle Endeavour is a familiar problem for NASA's
shuttle fleet.
NASA called a 24-hour
delay to Endeavour's scheduled STS-127 lift off to investigate possible
damage after a powerful electrical storm hit yesterday and 11 lightning bolts
impacted Launch Pad 39A here at the seaside Kennedy Space Center.
The Florida coast is often the victim
of lightning, as frequent thunderstorms and even hurricanes come in from
the ocean on the East. If lightning does occur nearby, the giant metal space shuttle
standing tall atop its launch pad tends to attract the brunt of it.
Lightning – a discharge
of electricity from the atmosphere – usually targets the tallest thing
around. The space shuttle stands a towering 184 feet (56 meters) high, on top
of a mounded pad. In addition to its height, the shuttle and its accompanying
structures are mostly made of metal, which is a good conduit for electricity,
so collects more of it.
"The launch pad gets hit all the time," said NASA
spokesman Allard Beutel. "We've never had a direct hit [to the shuttle
itself], though."
He estimated the pad had been struck dozens of times, though
luckily no catastrophic damage has been done to a shuttle from lightning.
The space shuttles – composed of main orbiter, orange
external fuel tank and twin solid rocket boosters – have never sustained a
direct lightning hit because of NASA's Lightning Protection System. A tall
metal lightning rod is installed on top of the Launch Pad to attract nearby
lightning and route the electricity away from the shuttle through a series of
attached metal wires.
"The Lightning Protection System takes the charge and
channels it away," Beutel told SPACE.com.
In 2006 the space shuttle Atlantis postponed
its STS-115 flight after a powerful lightning bolt impacted with a current
of 100,000 amps – the strongest lightning strike yet.
And lightning isn't just a risk while the vehicles sit at
the pad; If lightning struck a shuttle during flight the results could be
disastrous, as the shuttle contains sensitive vital electronics and flammable
propellant. The rocket's pyrotechnic system – the fuel materials that undergo
chemical reactions to ignite and thrust the shuttle space-ward – could easily
ignite if hit with a powerful electric shock.
That's why NASA takes careful precautions not to launch if
there is a chance of an electrical storm in the area. The metal shuttle could
even cause a lightning bolt while flying through the sky.
"Rockets can trigger lightning by channeling electrical
charge in clouds," Beutel said.
Airplanes have also been known to be struck
by lightning.
So why does NASA launch space shuttles from this
lightning-prone spot?
"We're closest to the equator," Beutel said.
"The Earth's rotation gives an extra push, so you use less fuel to get
up."
When rockets lift off from Cape Canaveral, the planet's spin
this far south helps loft the vehicle into orbit easier than from a location
toward the north of the United States.
SPACE.com is providing continuous coverage of STS-127
with reporter Clara Moskowitz at Cape Canaveral and senior editor Tariq Malik
in New York. Click here
for mission updates and SPACE.com's live NASA TV video feed. Live launch
coverage begins at 2:30 p.m. EDT (1830 GMT).
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