Monday, October 20, 2003

Warfare at the speed of light

He straps on emerald green goggles. A technician stabs a fire button and calls out the computer countdown. "Three ... two ... one ..."

Then ... nothing. Just a buzz of electronics and an ephemeral glow in this darkened room at Lawrence Livermore Laboratory. But inside Yamamato's target chamber, a block of steel spits flame and molten metal.

In those two seconds, 400 blasts of light poured into slabs of clear, manmade garnet. Swollen in energy, the crystal's atoms then unleashed torrents of infrared light to ricochet 1,000 times between two mirrors and multiply, finally escaping as 400 pulses of pure, square beam.

Kilowatt for kilogram, this is the world's most powerful solid-state laser. Its invisible beam drilled Yamamoto's inch-thick steel plate in two seconds. Add larger crystals and it will eat steel a mile or more away.

"What we're building," Yamamoto explains, "is a laser weapon."

After sinking 40 years and billions of dollars into beam weapons, defense scientists are on the cusp of what could be a military revolution -- warfare at the speed of light.

A laser arms race already is under way, chiefly in California. The prize is billions of dollars. Three families of high-energy beams -- powered by combusting chemicals, electron accelerators and crystals, such as Yamamoto's -- are vying for the Pentagon's eye.

Defense contractors are sniping at each other's designs, and corporate alliances are shifting. But no one seems to doubt that battle lasers -- perhaps mounted on Humvees, jet fighters and unmanned aircraft -- could knock down previously untouchable targets such as artillery shells, mortars, surface-to-air missiles and even cruise missiles at ranges of up to dozens of miles in good weather. In clear air above the clouds, a high-powered laser could lance out 500 miles to destroy rising ballistic missiles.

Is the United States willing to defend or attack satellites with lasers? The Air Force's Airborne Laser is to start test-firing against missiles in 2004. But the longer range of its laser in the thinner, upper atmosphere brings space vehicles within targeting.

How will other nations respond? Experts believe the United States could enjoy a near monopoly on battle lasers for years. But under what circumstances will it justify their use in the face of likely international opposition?

Ballistic warheads can strike at speeds greater than Mach 20. But readying them for launch takes several minutes at least and delivering them several more. Lasers race to target at roughly Mach 860,000.

The era of battle lasers began in the mid-1990s, when military scientists in New Mexico burned a hole in a Scud missile standing miles away. Soon after, a powerful chemical laser funded by the Pentagon and the Israeli Defense Force began blasting rockets and artillery shells out of midair. Scientists think such lasers have promise for knocking down mortar shells.

Defense theorists already are performing computer simulations of laser battles. "What it does is change the battlefield," said Thomas McGrann, a military operations analyst who runs battle simulations in Livermore Lab's Q Division. "What we're seeing is, he fires something at me, I knock it down. Anywhere from one to three kilometers out, I'm going to suppress his fire. And when he sends his UAVs (unmanned aerial vehicles) up -- and they're hard targets to kill -- I can take them out. An Army guy says he's taking fire from a wooded hillside. We start a fire there."

But forget about "Star Wars" and blaster pistols knifing the air with multi-colored beams. Visible lasers so far don't pack sufficient punch over distance to be useful weapons.

The laser battlefield will be largely invisible. Targets will explode, break apart in midair or burst into flame without apparent cause.

Soldiers won't buckle themselves into a laser cannon. The earliest battle laser systems are designed to defend U.S. troops and aircraft against airborne shells and missiles. That means computerized systems for tracking, targeting and firing faster than humans can react.

And the world's first laser weapons won't be worn on the hip: The most technically mature candidates are sprawling monstrosities weighing 50 tons and filling the better part of a Boeing 747 or, in the case of Northrop's MTHEL, a full-sized drug store, backed by chemical tanks or factories to recharge the lasers.

That's been the story of laser weapons for years. Chemical lasers are proven at delivering high-powered beams at great distances -- if they have enough chemicals. Scwartz' challenge is shrinking its laser by a fifth, to fit inside two cargo containers, packed inside a C-130 cargo plane.

"Can we do it?" he said. "We think we can."

But some Army officials are wary of hauling tanks of flammable, toxic chemicals into a war zone. A former Pentagon official noted that a .50-caliber armor-piercing/incendiary bullet could ignite a toxic explosion.

Once the laser stops firing, it must vent hot chemicals. That chemical and thermal signature could make a weapon traveling in two tractor trailers a conspicuous target.

Ultimately, battlefield lasers will have to be more compact, mobile enough to fit in the tail of the helicopter, in the belly of a jet fighter or in the backseat of a Hummer.

"Solid-state lasers seem to be the ideal for laser weaponry," Thompson said. "The basic design seems to be less complicated than either free-electron or chemical lasers and it seems to be more easily incorporated, say, into a fighter. They have more potential over the long run because of their potential compactness and the flexibility of their power sources."

Experts agree battle lasers need at least 100 kilowatts of power. The Pentagon wants to see who will get to 25 kilowatts first in 2004.

Yamamoto is a veteran builder of lasers and atom smashers. Next to those, the laser weapon sitting on his lab bench is easy: It's modular. He just adds another 4-inch slab or two of manmade garnet and surrounds it with diodes. He expects to beat 25 kilowatts by Christmas and double it early next year. To reach 100 kilowatts will take more and bigger slabs.

But the real innovation that makes solid-state lasers worthwhile for defense are high-power diodes. Instead of using flashlamps like Maiman's ruby and the National Ignition Facility, Yamamoto's laser is pumped by more than 8,000 diodes. They're 10 times as efficient.

In theory, that means a liter of everyday Army diesel fuel costing as little as $1 will generate enough rapid-fire laser pulses to destroy a standard airborne missile. The job now falls to Patriot missiles costing $3 million apiece.

The question is, will solid-state lasers that today resemble science projects, full of glass, mirrors and banks of sensitive electronics take the beating of battle?

"You have to get these lasers out in the field to see if they work. If you hit a bump in the road, do they hold up? Do you need five Ph.D.s to make them work?" said General Atomics' Campbell.

Moreover, all laser guns will, for the forseeable future, remain fair-weather weapons. Airborne particles and vapor diffuse the beam and cut its range enormously. Smart adversaries will attack under cover of smoke or inclement weather.

"In the first order, lasers are not going to work on bad days," Campbell said. "They're just not."

But then, neither do so many of the optical sensors on which U.S. forces depend for information-accelerated warfare.

"I'm sure there will be many games to be played in measures and countermeasures and counter-countermeasures," said Northrop's Scwartz. But the rule of thumb is "if you see a target, you can kill that target."

Ian Hoffman Oakland Tribune