Robotic Mirror Fleet May Boost Boeing's Airborne Laser Accuracy
Ballistic missile defense via airplanes mounted with lasers may seem straight out of science fiction, but add a fleet of UAVs with mirrors to increase the laser's range, and military insiders say the system might just work.
By Erik Sofge
Published on: October 6, 2008
In the history of comic books, rarely has a mastermind come up with a weapon quite as unabashedly cool as the Airborne Laser. Take a relatively standard Boeing 747 aircraft, and load it with a massive chemical laser. And not just any laser, but a megawatt-class beam weapon with an impressive name: COIL, short for Chemical Oxygen Iodine Laser. Thanks to a deformable mirror that changes shape using hundreds of twitching actuators, the Airborne Laser (ABL) can account for the atmospheric turbulence that would normally distort and smother a beam traveling at long distances. Throw in a fire-control system that can hit a fast-moving target from hundreds of miles away, and an infrared beam that's invisible to the naked eye, and ABL seems like the sci-fi definition of death from above. It even looks cool, with a turret jutting out of the nose of the plane.
And it gets better. The flying laser cannon could be accompanied by a fleet of unmanned aerial vehicles (UAVs) fitted with mirrors. These relay UAVs would be harder to spot and more disposable than a 747, and could bounce the high-energy beam onto targets that might otherwise be out of range, or out of the plane's line-of-sight. With multiple flying drones, a single ABL could cover an exponentially wider area. It would be an entirely new combination of lasers and robots—and it may be the answer to critics aiming to dismantle ABL before it ever flies.
Originally commissioned by the United States Air Force, this flying laser is now touted as a mobile missile defense platform, designed to shoot down ballistic missiles before they escape the atmosphere. If North Korea or some other hostile nation were on the verge of launching a strike against the United States or its allies, a small fleet of ABLs would be deployed to the region. They would loiter at altitudes as high as 40,000 ft, and if a missile did appear over the horizon, a laser would automatically dart out, painting the threat with enough heat to send it tumbling back to Earth.
It's this mission that has made ABL a target for critics of ballistic missile defense. The problem is one of feasibility, they say. A directed-energy weapon capable of getting close enough to matter, and of overcoming atmospheric disturbance and simple countermeasures, sounds like the stuff of comic books for a reason—it defies physics and strategic realities, or so these critics claim. "All the enemy has to do is paint its missiles with ordinary white paint, or have them be shiny, with a silvery, reflective surface," says Philip Coyle, who served as an assistant secretary of defense from 1994 to 2001. "White paint can reflect 90 percent of laser energy. Now you need a laser that's ten times bigger. It's already in a huge 747. How can you go any bigger?"
The Missile Defense Agency (MDA), which oversees new and existing missile-defense-related asset, generally refuses to offer specifics about countermeasures, and how its systems might overcome them, but in an e-mail response, an MDA spokesman wrote that ABL's initial ground tests incorporated a beam directed at a missile body painted white, and that, "In simple terms, the white paint had no effect on the lethality of the directed energy beam and did not require a longer duration lase, nor did it result in a reduction of energy required to burn through the booster case." Ground tests have also attempted to recreate the temperature fluctuations and other conditions that lead to atmospheric turbulence, and ABL's adaptive optics have reportedly performed within expectations.
Reassurances from MDA and Boeing notwithstanding, proof of ABL's technical feasibility could come next summer, when the system is expected to attempt a shootdown of a boosting missile. The test is slated to take place off the coast of California's San Nicolas Island, part of the government-owned Pacific Missile Range. However, the question of strategic feasibility could be harder to answer. "Even if they were able to make the system work, because the range is so short, it would have no military utility with Iran," says Wade Boese, Research Director for the Arms Control Association, a nonprofit based in Washington, D.C. "Iran is not going to be firing a ballistic missile from territory that's within military reach of the United States." Boeing and MDA will only say that the system's range is in the hundreds of kilometers, leaving skeptics to speculate as to how easy it would be to shoot down these relatively defenseless but extremely expensive (as much as $2 billion apiece) 747s.
For now, ABL's fortunes appear to rise and fall with its sponsor's, the MDA. This is a politically dangerous position. Congress has already called for an investigation into the utility of ballistic missile defense, and there's no guarantee that the embattled agency will survive the next presidential administration. To become indispensable—or at least worthy of continued funding—ABL might need to prove its versatility. That means new kinds of targets for its chemical laser, beyond ballistic missiles.
According to Mike Rinn, Boeing's Program Director for ABL, the search for additional missions is underway. "We're looking at what kind of modifications you would do with the system, to give it capability for other targets," says Rinn. "Air-to-air missiles, even other tough missions, like cruise missiles, surface-to-air. Or maybe even air-to-ground missiles, the kinds of weapons used to attack a fleet."
ABL might also possibly serve a role in open, conventional warfare, acting as a screen against missiles headed for assets on the ground, at sea, and in the air. But unlocking ABL's full potential, says Rinn, could require robots. Or, more specifically, a fleet of UAVs carrying relay mirrors.
Instead of barging into hostile airspace with a full fighter escort, and hoping for a clear shot at any and all enemy missiles, a single ABL could function as a kind of flying laser–artillery piece. The UAVs would act as forward observers, extending the effective range of the system, and finding and targeting threats that might otherwise be obscured or hidden.
It smacks of science fiction, but Boeing has been researching the potential of relay mirrors for years. Although much of this work has slowed or halted because of the ABL program, the company has already built a relay mirror demonstrator in Albuquerque, New Mexico, as part of its Aerospace Relay Mirror System program. The 15-ft.-tall relay device consists of two mirrors—a receiver, which is the target for the incoming laser, and a transmitter, which aims the redirected beam. So far, the system has only been tested using a low-powered, sub-kilowatt-class solid-state laser, with the relay suspended 100 ft. in the air with a crane.
A related program, the Tactical Relay Mirror System, focused on using UAVs to bounce nonlethal beams to extend communication networks or provide targeting data for guided munitions. Developing a fleet of laser-bouncing robots would mean essentially marrying these programs, and in an e-mailed statement, Boeing laid out some of the specific requirements of relay UAVs, saying that, "For a theater or strategic application, as with ABL, the best carrier must be capable of long endurance at high altitudes, the longer and higher the better. For tactical applications, as with a ground-based laser source, the carrier does not need to operate above 1.2 miles altitude (generally) and must be mobile enough to maintain a ground distance from the source of not more than 5 to 10 kilometers. Fixed-wing, rotary-wing and aerostat carriers have been considered for this role."
Boeing also stated that, "For optimum effectiveness, the relay mirrors (both receiver and transmitter) should be approximately the same size as the ABL primary mirror." It isn't clear whether any existing UAV would be able to carry a pair of 62-in.-dia mirrors, along with the necessary beam-control system. There's also no specific timeline for the development of relay drones or other compatible relay platforms. But Rinn believes that, despite the obvious technical hurdles, this type of capability is the next logical step for ABL. "That's where we'll be," Rinn says. "Today, we're showing a simple demo. But with a fleet of these relay mirrors, distributed among a picket line, you could see a handful of ABLs with huge reach in the coming decades."
