Cutting Edge

Beam control optics in the Airborne Laser system stabilize and shape the beam emitted by the chemical oxygen iodine laser en route to the nose turret of the aircraft.

(Credit: Russ Underwood, Lockheed Martin)

The Airborne Laser may have lost favor in Washington, but it's still going strong at Edwards Air Force Base.

Boeing, the prime contractor for the directed-energy weapons system, said Thursday that the ABL's high-energy laser earlier this week was fired in flight for the first time--though not at an external target. Instead, in a flight over California, the laser beam traveled only as far as an on-board calorimeter, which measured the beam's power. Boeing didn't say what that measurement was, but the system is generally referred to as "megawatt-class."

The Airborne Laser in flight.

(Credit: Boeing)

The one-of-a-kind ABL was built to test out and ultimately show off what a laser beam can do to a ballistic missile fired in anger. The goal, if and when all systems are go, is for the laser-equipped aircraft to home in on an ICBM while it's still early in its trajectory, holding the laser beam on the missile long enough to rupture its skin and thus knock it out of commission.

Ambitious plans for the Airborne Laser, however, have been considerably scaled back. Earlier this year, in revamping the Pentagon's budget and operations priorities, Defense Secretary Robert Gates said that a second prototype would not be built.

The core of the existing ABL is a chemical oxygen iodine laser, or COIL, and it's hardly man-packable machinery. The COIL system itself takes up the back half of a modified 747-400F, while the front half of the jumbo jet is given over to the beam control/fire control system.

Given that an aircraft in flight can be a fidgety beast, the ABL's ability to maintain precise alignments was a notable accomplishment, according to a Thursday press release from Northrop Grumman, which designed and built the high-energy laser:

ABL has to keep all of the powerful laser's optical components perfectly positioned as the aircraft vibrates and flexes during flight...Since we were unable to fly the kind of large concrete pads used to hold a ground-based laser's optics in place, we had to isolate the COIL's optics from the structure but also maintain alignment. So the team developed an optical bench isolation system that isolates disturbances caused by normal aircraft operations while maintaining alignment to the gain medium, or the source of a laser's optical power. It's like an automobile's 'smart suspension' that keeps the car riding smoothly at the same level over a bumpy road.

Last week, in a continuing series of piecemeal tests, the ABL engaged in an in-flight trial run against an instrumented target missile. The aircraft used its infrared sensors to locate the missile, then fired a pair of solid-state illuminator lasers that tracked the missile and gauged atmospheric conditions. "This test demonstrates that the Airborne Laser can fully engage an in-flight missile with its battle management and beam control/fire control systems," Michael Rinn, Boeing vice president and ABL program director, said in a statement. "Pointing and focusing a laser beam on a target that is rocketing skyward at thousands of miles per hour is no easy task."

A number of increasingly complex tests still lie ahead for the ABL, including firing the high-energy laser through the Lockheed Martin-developed beam control/fire control system and out of the nose-mounted turret. Before the end of the year, Boeing expects to do a full-fledged intercept test against a ballistic missile.

A Northrop Grumman Space Technology engineer in Redondo Beach, Calif., monitors a solid-state laser, in a photo from January 2007.

(Credit: Northrop Grumman)

From the week gone by on the directed-energy weapons front: defense contractor Northrop Grumman reported that it got a solid-state laser to fire a beam with a potency of 105.5 kilowatts.

For the ray-gun wing of the military-industrial complex, the 100-kilowatt threshold is a major milestone, marking the entry point to weapons-grade laser weapons. Adding to the appeal is that solid-state lasers are much more compact, and less noxious, than chemical laser systems such as the one in the works for the 747-centric Airborne Laser.

The technical details of Northrop's achievement break down this way, starting with a modular, "building block" approach that bodes well for scalable systems, the company said:

For building blocks, the company utilizes "laser amplifier chains," each producing approximately 15kW of power in a high-quality beam. Seven laser chains were combined to produce a single beam of 105.5 kW. The seven-chain JHPSSL laser demonstrator ran for more than five minutes, achieved electro-optical efficiency of 19.3 percent, reaching full power in less than 0.6 seconds, all with beam quality of better than 3.0.

Adding an eighth chain that the system was designed for would increase laser power to 120 kilowatts, Northrop says.

Where this test saw five minutes of continuous operation for the laser, altogether the system has been operated at above 100 kilowatts for a total duration of more than 85 minutes.

The efforts are part of the Pentagon's Joint High Power Solid State Laser (JHPSSL) program.

Even though 100 kilowatts has long been the "proof of principle" sought for weapons systems, Northrop says that "in fact, many militarily useful effects can be achieved by laser weapons of 25 kW or 50 kW, provided this energy is transmitted with good beam quality, as our system does."

Of course, this is still a laboratory laser system and not a field-tested, ruggedized product. "It is still a little heavy and a little big," Dan Wildt, vice president of Northrop's directed energy systems program, told the LA Times.

Shiny on the outside, sparkly on the inside? This is Northrop's laser weapon system demonstrator.

(Credit: Northrop Grumman)

That's probably a significant understatement. Says Noah Shachtman at Wired's Danger Room blog of the news from Northrop:

Does that mean energy weapons are a done deal? Hardly. There are still all sorts of technical issues--thermal management and miniaturization, to name two--that have to be handled first. Then, the ray gunners have to find the money. The National Academies figure it'll take another $100 million to get battlefield lasers right.

In a separate post, Shachtman reports on what's involved in getting specific laser systems ready to go over the next several years.

Earlier this year, Boeing said that it had used a "kilowatt-class" solid-state laser to shoot down a UAV from a ground-based system. The company hopes that the Airborne Laser, meanwhile, will do its first-ever aerial target shoot sometime in 2009.

There's still a lot of blue sky in Boeing's plans for directed-energy weapons like the Laser Avenger.

(Credit: Boeing)

Updated 2:40 p.m. with details on how the laser damaged the UAV and on the Laser Avenger's targeting system.

Boeing is seeing a glimmer of progress in its work toward fielding laser weapons.

The defense industry giant on Monday said tests of its Laser Avenger system in December marked "the first time a combat vehicle has used a laser to shoot down a UAV," or unmanned aerial vehicle. In the testing, the Humvee-mounted Laser Avenger located and tracked three small UAVs in flight over the White Sands Missile Range in New Mexico and knocked one of the drone aircraft out of the sky.

Boeing didn't go into much detail about the shoot-down. In response to a query by CNET News, it did say this much about the strike by the the kilowatt-class laser: "A hole was burned in a critical flight control element of the UAV, rendering the aircraft unflyable."

While decades of Hollywood imagery may conjure up a vision of a target disintegrating in a sparkle of light, the actual workings of the laser beam are probably more prosaic. For instance, the beam from Boeing's much, much larger Airborne Laser, which is intended to disable long-range missiles in flight, uses heat to create a weak spot on the skin of the missile, causing it to rupture in flight. Boeing hopes to conduct the first aerial shoot-down test with the much-delayed 747-based Airborne Laser later this year.

In tests in 2007, the Laser Avenger "neutralized" improvised explosive devices (IEDs) like those that have been a deadly threat in Iraq, along with other unexploded munitions.

The U.S. Air Force has awarded Boeing a new contract worth up to $30 million for the next phase of development on the Advanced Tactical Laser.

The ATL is a C-130H aircraft outfitted with a 12,000-pound high-energy chemical laser module that would be used as a weapon against ground targets. It's the smaller sibling of the Airborne Laser, a highly modified 747 under development that packs a similar weapon but that would be used against ballistic missiles.

The Advanced Tactical Laser will use a rotating ball turret to fire its laser weapon at ground targets.

(Credit: Ed Turner, Boeing)

While the 747-centric ABL is designed to fire its laser through a bulbous nose apparatus, the ATL totes a belly turret reminiscent of the manned versions used in some World War II bombers.

The new Extended User Evaluation contract marks the start of a transition for the ATL, which Boeing has been working on as an Advanced Concept Technology Demonstration project. The EUE phase means another round of ground and flight tests, along with "hands-on operation" for the Air Force and other potential users.

Why use a laser when the Air Force already has a wide array of missiles and bombs at its disposal? (The standard gunship variant of the C-130 can already be equipped with 40mm and 105mm cannons.) "Little to no collateral damage," Boeing says, thanks to the laser weapon's "ultra-precision engagement capability." That is, think laser pointer with extreme prejudice.

In addition, the laser would presumably strike more or less silently--no thump-thump-thump or rat-a-tat-tat. (Note, 11:30 a.m. PDT: A reader writes in to say that high-power lasers operating in the atmosphere are anything but silent, perhaps because of ionizing the air - a la lightning.)

For use against missiles, mortars, and the like, laser weapons are intended to heat up and weaken the metal skin of the projectile, causing it to rupture while in flight. Against ground targets, the ATL could, say, zap fuel tanks or even vehicle tires--if it could hold focus long enough.