Dawn of the Airborne Laser
R. A. Hettinga
Sun, 9 Mar 2003 14:53:49 -0500
Popular Science |
March 9, 2003
In a starkly sanitized clean room, a stocky Lockheed Martin engineer wearing a shower cap and laboratory smock scuttles in and about black plastic curtains, talking with near-manic intensity and flashing his bright eyes and wry smile. "Want to see something really cool?" asks Paul Shattuck as he yanks back the curtains, revealing a maze of psychedelically colored optics and black anodized metal hardware. "This," he says, "is what they call the Wall of Fire."
The Wall of Fire, a dark, forbidding and mostly classified conglomerate of glass and high-tech hardware 12 feet long, 12 feet wide and 3 feet thick, sits in jarring contrast to the bright white blinding hues of this cavernous, four-story-high room. The contraption is like a black hole, swallowing the light and giving none of it back.
On the floor is an outline of a 747; the Wall of Fire sits poised in the cargo hold of the imaginary aircraft. The device is packed with precision-ground mirrors and lenses with anti-reflective coatings, which provide the spooky spectrum of iridescent colors that seem to shimmer with every movement of your eye. Many sections of the Wall of Fire are concealed. "Dust," the engineers lurking about say, repeatedly. Odd, given that this is a clean room. "OK," they confess, "it's covered up because of you."
But I see enough to get the point: The Wall of Fire means business. If all goes according to plan, this finely tuned apparatus, soon to be mounted behind a fast-moving turret in the nose of a 747, will help produce a laser beam so powerful that it could destroy a missile moving at several times the speed of sound in the ascent after launch.
Shattuck directs the program at Lockheed Martin Space Systems in Sunnyvale, California, that will provide Boeing, the project leader, with the beam- and fire-control optics for the prototype YAL-1A Airborne Laser (ABL). Lasers have long been used to cut tile, correct vision, weld with extreme precision and, yes, point to things on chalkboards; except in Star Wars or Star Trek, however, no laser has ever been successfully fired in anger. But when all the components of the ABL are installed in a 747 later this year, it could become the world's first functional laser weapon?at a time when the need for such a weapon couldn't be more urgent.
With any number of rogue nations and terrorist groups developing ballistic missiles, armed with conventional explosives, such as Iraq's Scuds, or nuclear warheads, modern warfare has become treacherously unpredictable. Unlike intercontinental ballistic missiles, the shorter range and lower maximum altitude of intermediate-range ballistic missiles like Scuds require instant reactions if the missiles are to be destroyed. Most previous antiballistic missile systems, which usually involve firing missiles at missiles, have had limited success. They haven't been able to get close enough to the Scuds to shatter and destroy them, let alone score direct hits. Lasers, though, travel at the speed of light and can be tuned perfectly to bull's-eye a moving object hundreds of miles away. "When talking about the ability to put force on target, there is nothing faster or more precise than a laser," says Air Force Col. Ellen Pawlikowski, who heads the $1.6 billion ABL program.
The laser weapon project, run by the Missile Defense Agency for the Air Force, has already met significant benchmarks. A modified Boeing 747 made its first flight, sans laser but with the new nose turret in place to test its aerodynamic impact, last July 18. The high-energy laser?the chemical oxygen-iodine laser that actually attacks the missile?built by Northrop Grumman Space Technology (formerly TRW) reached 118 percent operating power during a successful test firing at the company's facility near Los Angeles six months earlier. Next step: The laser will be installed in the 747 this summer and, following more tests, will be on track to the make-or-break goal of shooting down a Scud-like ballistic missile by the end of 2004 or early 2005. At that point, the prototype could conceivably become an operational emergency-use weapon while a fleet of seven or more laser-equipped aircraft is being built. Shattuck exudes confidence. "These are mature technologies, and the real challenge has simply been integrating all of them into a working airborne platform," he says. "Now we're in the final phase of that, putting all of the pieces into one end-to-end system and just wringing it out."
On a mammoth ramp at Boeing's Wichita Development and Modification Center in Kansas sits the 747-400F freighter, which is undergoing conversion into one of the largest single weapons ever devised. The Air Force purchased the aircraft new in 1999, painted it the service's customary gray, and outfitted it with a bulbous black nose to house the turret.
A swarm of technicians are installing control consoles, electronics, and test and support gear prior to the airplane's departure for Edwards Air Force Base (which occurred this past December 19). Mark Dannar, the Boeing ABL Aircraft Integrated Product Team co-leader, jogs up the access stairs and into the voluminous main hold, which will house both the system operators and, behind a massive airtight bulkhead, the high-energy laser, the system's knockout punch. Walking over to a rack of electronics peppered with lights and knobs, Dannar grins and says, "Look at this switch?it's marked Executive Laser Controller." Like so many others involved in the project, he's smitten with its inescapable sci-fi edge. Walking back towards the tail, he surveys recent work. "There isn't a system onboard this aircraft that we haven't touched," he says, "and we had to solve a lot of serious engineering challenges."
For one thing, the inside of the freighter was beefed up to accommodate the six van-size modules that will generate the laser beam from the rear of the plane. Outside, Dannar points out the numerous places where the aircraft's skin was pierced to install the ABL's detection equipment. This is the gear that will identify and target incoming missiles.
Here's how it will happen: Six infrared sensors positioned on the fuselage will constantly scan all directions for hot missile exhaust plumes, which they can do autonomously or at the prompt of launch-detecting satellites. When one, or several, is located, the ABL's multiple separate lasers will swing into action?all within seconds. A laser ranging pod atop the plane's cockpit, right now almost four stories above us as we stand on the ground, will spin around to face the first missile?the one the computer has determined is most threatening ?and measure its distance with a carbon dioxide laser. The track illuminator laser, fired through the 12-inch aperture of the Wall of Fire and into the nose turret, will compensate for aircraft vibration and then pinpoint a specific area of the missile to aim at. The beacon illuminator laser, also fired through the nose turret, where a cassegrain reflector telescope expands the beam's dimensions to 1.5 meters, will then use the beam-and fire- control unit's adaptive optics to characterize the missile's dimensions. (These optics, standard equipment on all the ABL's turret-fired lasers, extend their range with mirror-flexing technology to compensate for atmospheric turbulence.) Finally, the computer will fire the high-energy laser, which will focus down from 1.5 meters in diameter to a much smaller spot of light by the time it reaches the target. As the laser dwells on the missile's flank for 2 or 3 seconds, the oxidizer or fuel tank will rupture and the missile will explode. I ask Dannar how the crew will know whether the mission has been accomplished. "If it blows up, you got it," he says, smiling.
The ABL will carry enough reactants for about 20 shots on target, which will be generated in the plane's six rear modules by combining hydrogen peroxide and chlorine gas to produce an excited form of oxygen known as singlet delta oxygen (SDO). Iodine granules are cooked in onboard ovens, forming iodine gas that is injected into a cavity with the SDO, which excites the iodine and "pumps" the laser. As the excited iodine relaxes to its base energy state, photons with the wavelength of 1.3 microns are produced. The photons, bouncing around inside a long cylindrical resonator, are then gathered and sent down a long tube toward the front of the fuselage and the turret. This stacking process?which occurs at fraction-of-millisecond intervals?generates a laser beam.
The Northrop Grumman test firing proved that the laser could generate the heat necessary to destroy a missile from a stationary mounting. The next obstacle was to show that this can be done from a buffeting airplane banking through the sky at 600 miles per hour, 40,000 feet above the ground. This required some serious slimming down.
"One of the key challenges has been to ?lightweight' the system, because we are putting this hardware on an airplane and dealing with the volume and lifting capacity of the airplane," explains Northrop Grumman's ABL Deputy Program Manager Gary Koop at the Systems Integration Lab at Edwards Air Force Base, where the laser components are being inserted into a retired Air India 747 to make sure they fit prior to final installation in the YAL-1A. The weight reduction was achieved with lightweight materials such as titanium, a new range of plastics and new composite materials. But the ABL also needs to survive in a highly dynamic environment. "When we build lasers in a ground facility, we pour thousands of pounds of concrete to make a stiff foundation," Koop says. "Boeing designs airplanes to be flexible to absorb all the aerodynamic loads. So we have one system, the plane, that wants to move, and one, the laser, that wants to be rigid." The solution to that came through the development of multi-axis shock absorbers that keep certain components along the laser's path steady as the aircraft moves around it.
It has taken decades of similar engineering advances to make the ABL feasible. The military has been noodling around with laser weapons since the early days of the cold war. The United States and the former Soviet Union both conducted experiments with nuclear-powered naval and satellite-based lasers, all intended to bring down intercontinental ballistic missiles and bombers. Eventually, the idea became the central component in the now-abandoned Star Wars program floated during the Reagan administration. The technological breakthroughs generated by that failed program were folded into the ABL effort.
Despite the self-assurance surrounding the ABL among Air Force personnel, critics outside the program doubt the effort will pan out. "I'm deeply skeptical about achieving the laser power output required to destroy a missile," says Subrata Ghoshroy, a Harvard research fellow and senior associate at the Federation of American Scientists who has worked on past military laser projects. According to Ghoshroy, Northrop Grumman's ground-test success is only partially conclusive; once the laser is in the air, many factors will interfere with the beam quality, including moisture and air turbulence, which the adaptive optics may not be able to sidestep entirely. "There is very little experience in the whole process of building a high-power laser and intercepting a missile with it," Ghoshroy notes.
Others think the laser itself will work but could fail in its prime mission; in other words, that the ABL may be better suited for attacking long-range intercontinental ballistic missiles and satellites than short-range weapons that operate within relatively compact geographic areas. "Theater ballistic missiles have shorter-powered flight time at lower altitudes where the atmosphere is denser," says Ted Postol, a professor of science, technology and national security policy at the Massachusetts Institute of Technology. "Going against an ICBM would be easier because the missile undergoes longer-powered flight, and the intercept would occur in less atmosphere."
The ABL still has a host of milestones to achieve before it quiets the naysayers. After it's airborne in a couple of years, it will attempt to hit dead-on a series of target boards suspended from balloons, followed by objects towed behind a high-altitude aircraft. Sounding rockets launched from White Sands Missile Range in New Mexico will serve as the next round of targets, and the ABL's final test will be to shoot down a ballistic missile similar to a Russian Scud.
If all goes well and the ABL is accepted into service, the laser might qualify for any number of other missions. Perhaps the most novel application for the ABL is the possibility that it may be used to shoot down enemy planes. That was suggested in a recent Air Force report that said this could be accomplished by using mirrors mounted on airships to extend the range of the laser beam and deflecting a beam straight down onto targets rather than at oblique angles through dense atmosphere. "In our study, the time-on-targets were reasonable," says Ted Wong, the retired laser scientist who led the Air Force panel. "A matter of a few seconds on target seemed enough to cause damage. A lot of targets we're looking at are not that hard. Aircraft, sensors and radars can be (highly vulnerable) to thermal effects."
In the meantime, Congress is so pleased with the results of the ABL project that it has already appropriated money to purchase a second airplane for conversion into an ABL?a passenger version of the 747-400 with an extended upper deck to house the entire crew, eliminating the current, highly complicated airtight midcabin bulkhead separating the crew from the laser. This airplane will likely be the first to become truly combat-ready. If the project does get that far, decades of secret laser efforts will finally emerge from the world of briefing presentations and war games to become hardware. After long yearning for the power of the gods, the United States may soon be able to deliver a bolt from the blue.
Mark Farmer, a writer and photographer in Anchorage, Alaska, maintains an action-packed Web site: www.topcover.com .
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