Military Lasers Will
Change The Face Of Warfare
"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."
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.
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.
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.
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.
Backers say the airborne laser will change the way America defends itself.
"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."
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.
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.
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.
"I think we're just beginning to open the door," says Shennum, who compares the invention to the creation of radar or stealth technology.
Fire One!
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.
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.
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.
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.
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.
"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."
But the laser blast, which is invisible, is vulnerable to distortion in the atmosphere.
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.
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.
Shaping the beam
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.
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.
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.
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.
Since the mirror is really a flying telescope, it could also be turned toward the ground for closer looks at the enemy.
Powerful blast
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.
The laser is created by the Chemical Oxygen Iodine Laser, which mixes common chemicals in a way that produces an uncommonly strong blast.
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.
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.
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.
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.
"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."
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.
Within five seconds, the laser beam breaches the shell of the missile's rocket booster, causing the missile to explode.
New way to fight
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.
Booen says the laser is designed never to miss its target. It won't fire if it doesn't have a shot.
Another key technology of the '90s that allows today's scientists to do what their 1960s counterparts could not is the modern supercomputer.
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.
The computer allows engineers to put systems through tests without taking the time to build each part.
"This Star Wars technology is reality today," Shennum says.
"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."
By Robert Davis, USA TODAY