11/09/2011 - 13:36

Coming not so soon to a theater near you: Laser weapons for missile defense

Subrata Ghoshroy

Subrata Ghoshroy

Ghoshroy is a research associate at the Massachusetts Institute of Technology's Program in Science...

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Once upon a time not so long ago, glossy posters, press releases, and other public relations materials flooded congressional offices and newsrooms inside Washington's Beltway, touting the futuristic antimissile project known as the Airborne Laser (ABL). The publicity campaign included an artist's rendition of a Boeing 747, modified so a reddish laser beam shot from its nose turret. As if they were publicizing a blockbuster movie, ABL posters carried the words "Coming soon to a theater near you."

The Airborne Laser was to be the Pentagon's primary boost-phase weapon against short-range missiles like the Soviet Scud and its descendants now fielded by Iran and North Korea. The system would employ a megawatt-class chemical laser mounted on a modified and reinforced Boeing 747-400 cargo aircraft that would loiter near the battlefield, ideally at a standoff distance -- hundreds of kilometers from enemy territory -- at an altitude of about 40,000 feet. It was supposed to have an autonomous search and acquisition system that would track rising ballistic missiles and destroy them with a Chemical Oxygen Iodine Laser (COIL).

In theory, the ABL was a high-tech dream weapon: Once an enemy missile was detected, the ABL would acquire its trajectory and, after the missile rose above cloud cover, follow it precisely with a laser. A second laser would probe atmospheric turbulence, and an onboard adaptive optics system would correct the main laser beam so it delivered the proper amount of energy to the target missile. The system's delivery system would not only point the COIL beam precisely at a certain area of the fast-moving target missile but also hold it there for seconds -- perhaps tens of seconds -- until the missile surface heated and ruptured.

In reality, though, the ABL has been a practical failure and a procurement nightmare. After falling eight years behind schedule and going $4 billion over budget, the ABL program -- like several other directed-energy weapon programs that preceded it -- was finally axed in 2010. As then-Defense Secretary Robert Gates summarized for the House Appropriations Committee in May: I don’t know anybody at the Department of Defense … who thinks that this program should, or would, ever be operationally deployed. The reality is that you would need a laser something like 20 to 30 times more powerful than the chemical laser in the plane right now to be able to get any distance from the launch site to fire. So, right now the ABL would have to orbit inside the borders of Iran in order to be able to try and use its laser to shoot down that missile in the boost phase. And, if you were to operationalize this, you would be looking at 10 to 20 747s, at a billion and a half dollars apiece, and one hundred million dollars a year to operate. And there's nobody in uniform that I know who believes that this is a workable concept.

Critics of the ABL program -- in Congress and elsewhere -- recommended early on that a robust technology demonstration was essential before the Pentagon embarked on a hugely expensive program to deploy a weapon in the field, but to no avail. With unwavering support from defense contractors like Boeing, Northrop Grumman, and Lockheed Martin, zealots in the defense science community and Pentagon officials prevailed on Congress for nearly 15 years to fund the ABL, sometimes in excess of even what the Defense Department had requested.

Sold as a “mature” technology, in the end the ABL could not meet any of its primary specifications. It could not deliver the required power. It was too big and too heavy to be fitted into a Boeing 747-400 freighter, the biggest airplane available. (Although the dimensions of the laser are classified, it was clearly outsized. The original design called for 14 modules of the COIL; ultimately, only six could be accommodated.) Analysts repeatedly warned that the technology needed further testing before the government undertook the huge costs of attempted deployment, and the analysts were repeatedly ignored. The ABL is a classic defense boondoggle and a frightening example of how committed military officials, scientists, and defense contractors -- the now-clichéd military–industrial complex -- can persuade Congress to keep a defense program alive against, seemingly, all reason. And, perhaps, beyond all reason.

As it happens, the ABL was not totally eliminated, just downgraded to a new status, the Airborne Laser Test Bed, that will allow research into laser weapon technologies -- including a new type of laser that is, many familiar laser-weapons advocates insist, everything the old ABL was not.

A series of false starts. The LASER (Light Amplification by Stimulated Emission of Radiation) was discovered in the early 1960s, and it was not long before low-power laser devices, ranging from milliwatts to a few watts of power, made their way into our everyday life, in the form of bar code readers and DVD players. Medium-power lasers (hundreds of watts to a few kilowatts) also found applications in the precise cutting of metals, for example.

During the Cold War, the militaries in both the United States and the Soviet Union moved to develop high-power lasers as weapon systems.

The full contents of this article are available in the November/December issue of the Bulletin of the Atomic Scientists and can be found here.