- By the time Capt. James T. Kirk was blasting
fictitious Klingons with the starship Enterprise's phaser in 1966, the
Air Force had all but given up trying to invent a similar weapon to shoot
down missiles.
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- It didn't take long for scientists to
conclude in the early 1960s that the world's most powerful lasers were
too weak to punch holes in a missile and that aiming devices couldn't even
come close to tracking the fast-moving targets.
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- But today, the Air Force says, advances
in a variety of scientific areas " from astronomy to airliner design
" have led scientists to the brink of bridging that gap between science
fiction and reality.
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- A Boeing 747 jumbo jet is being built
and outfitted with one of the world's most powerful lasers. Within three
years, scientists say, this flying laser will shoot down its first Scud-type
missile much the way Capt. Kirk blasted those Klingons.
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- Backers say the airborne laser will change
the way America defends itself.
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- "We've got a weapon now that operates
at the speed of light," says Paul Shennum, vice president of the Airborne
Laser Program at the Boeing Co., which leads the private industry team
working on the project. "Try to develop countermeasures to a system
that deploys that kind of energy."
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- If the first airborne laser works as
expected, six more will follow. The cost of the program, from the first
ground tests to maintaining the seven aircraft for 20 years, is expected
to be $11.2 billion.
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- The Air Force says the program is needed
because 30 nations have more than 10,000 theater ballistic missiles on
which they can mount chemical, biological or nuclear warheads. The military
likes the idea of using the laser to destroy these missiles during their
boost phase, when they are climbing out of enemy territory. The warhead
and other debris would fall close to the launch pad, away from U.S. troops.
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- But beyond the military use, the scientific
leap also may lead to advancements in other areas, from spying to avoiding
turbulence on commercial airline flights.
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- "I think we're just beginning to
open the door," says Shennum, who compares the invention to the creation
of radar or stealth technology.
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- Fire One!
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- In the heart-pounding seconds after an
enemy missile has been fired at U.S. troops, an array of advanced technology
aboard the jet will focus on the airborne threat.
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- Today, missile launches are detected
and tracked from command centers in the USA. When crews back home determine
via satellites where the missile is heading, warnings are sent to take
cover.
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- The airborne laser jet will have a more
sophisticated laser tracking system that can pinpoint the position of the
missile as it races through the sky to within a fraction of an inch.
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- The jet, cruising at 40,000 feet hundreds
of miles from the missile, tracks the missile as it climbs at speeds ranging
from Mach 4 to Mach 5, or nearly five times the speed of sound.
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- For years the Air Force has tried to
find a way to down missiles during this boost phase, but the fastest tools
in the arsenal were fighter jets, which were too slow.
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- "You just can't close that loop
with an F-15," says Col. Mike Booen, director of the Airborne Laser
System Program Office at New Mexico's Kirtland Air Force Base. "Only
the speed of light can close that loop."
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- But the laser blast, which is invisible,
is vulnerable to distortion in the atmosphere.
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- Pockets of air that vary in temperature,
the same invisible forms responsible for the bumps air travelers know as
clear air turbulence, can act like prisms to distort the shape of the laser
as it passes through.
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- To counter this problem, designers use
the lasers that track the missile to measure the distortion in the air.
By measuring how much those lasers are distorted as they pass from jet
to missile and back again, computers calculate how to change the shape
of the laser weapon as it is fired.
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- Shaping The Beam
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- The key to this trick is "rubber
mirrors," which have been perfected by astronomers looking through
the atmosphere deep into space . Astronomers found that when a crooked
beam of light bounced off a crooked mirror, it could result in a straight
beam of light.
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- The mirror in the nose of the jet works
the same way, only faster, as the missile climbs through the air. Only
a few microns thick, this coated sheet of glass can be moved by finger-like
actuators to send the laser out in different shapes.
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- During the five-second shot, these actuators
can move thousands of times each second. The laser is distorted by the
mirror as it is fired and then is corrected by the air turbulence, which
basically focuses the beam on the target.
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- The laser team's understanding of turbulence
may someday help other scientists who are trying to perfect lasers to detect
and warn airline pilots of invisible turbulence. "We are learning
a lot about the atmosphere," Shennum says.
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- Since the mirror is really a flying telescope,
it could also be turned toward the ground for closer looks at the enemy.
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- Powerful Blast
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- Within a few seconds after the missile
is detected in the air, the settings for the rubber mirror are determined,
and the laser can be fired.
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- The laser is created by the Chemical
Oxygen Iodine Laser, which mixes common chemicals in a way that produces
an uncommonly strong blast.
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- While it was the science of looking to
the stars that led to the rubber mirror, the laser is based on a development
by a telephone company.
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- The first carbon dioxide laser came in
1964 when a Bell Telephone scientist named Charles Patel found that the
gas was a good medium for a laser. This kind of laser is now one of the
most powerful in the world.
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- But to work in flight, the beam must
pass uninterrupted from the back of the plane, where it is generated, through
the nose, where the rubber mirror is mounted. The team had to devise shock
absorbers for each part of the system to adjust for in-flight bumps.
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- Engineers flew a test 747 around the
world measuring vibrations with 128 pressure sensors. The tests showed
them how much they did not understand about how jumbo jets bump in flight.
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- "You would think the Boeing Co.
would understand how a 747 shakes, rattles and rolls," Shennum says.
"But passenger comfort is not like a laser."
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- As the laser passes through the nose
turret in the plane, it expands from a foot in diameter to 4 feet wide
" the size it will be when it hits the missile.
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- Within five seconds, the laser beam breaches
the shell of the missile's rocket booster, causing the missile to explode.
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- New Way To Fight
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- In battle, the plane would be protected
by fighter jets during its 12-hour mission. A tanker plane would refuel
the jumbo jet in flight after the first six hours of patrolling the skies.
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- Booen says the laser is designed never
to miss its target. It won't fire if it doesn't have a shot.
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- Another key technology of the '90s that
allows today's scientists to do what their 1960s counterparts could not
is the modern supercomputer.
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- The computer that Boeing used to design
the 777 commercial airliner allowed the airborne laser team to combine
the work of 22 teams in 11 states to perfect the laser weapon system.
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- The computer allows engineers to put
systems through tests without taking the time to build each part.
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- "This Star Wars technology is reality
today," Shennum says.
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- "This is just the first step,"
Booen says. "The next question is, how do we make it smaller? Can
we put this on a fighter jet? This really should alter the way America
fights war."
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