14 May 2010
'Star Wars' meets reality?
Military testing laser weapons
By Dan Vergano
Five decades after the creation of the laser, the ubiquitous technology of the modern era may be ready to serve up that Star Wars science-fiction staple: the laser blaster.
Advances in the technology have made it possible for military testers to shoot down incoming mortar rounds with land-based lasers, and military commanders are on the verge of being able to fire laser blasts from the air that could be aimed at tanks or mines.
"We literally are the invisible death ray, let me tell you," says Mike Rinn of Boeing's Airborne Laser Program in Seattle, a missile- defense effort, one among dozens of Defense Department-supported "directed energy" programs run by military contractors such as Boeing, Raytheon and Northrop Grumman.
"This beam is invisible to the naked eye; you can't see it."
Taking advantage of some simple physics, lasers have allowed humanity to harness light to cut holes in things and establish new forms of communication. The light from a light bulb or the sun, an unbunched blur of multiple wavelengths, is warm to our touch and can burn. Lasers' lenses focus the power of light into a tightly bunched beam to burn surfaces with fine accuracy. And the laser can read bar codes on consumer products and digitized recordings on DVDs and CDs by bouncing finely focused beams off surfaces and using a "photodiode" sensor to read variations in reflected light as a code.
Lasers ring up groceries, play movies and transmit phone service, and they are involved in many other aspects of our lives.
"Our modern society basically runs on lasers," says Thomas Baer, head of the Stanford Photonics Research Center at Stanford (Calif.) University. He's also a spokesman for the American Physical Society's "Laser Fest," which is celebrating the 50th anniversary of the technology.
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Since the 1980s, automotive companies have used lasers to cut the steel for their cars, today using ones in the 2,500- to 5,000-watt power range that can cut several hundred inches of steel a minute. Military research lasers now release 10 to 20 times more power, so there has been a leap in the potential to burn through metal in seconds.
Lasers increasingly are being used by the military, says Sharon Weinberger, author of Imaginary Weapons: A Journey Through the Pentagon's Scientific Underworld. Gun sights use lasers, targets are "painted" with lasers to help guide bombs dropped from aircraft, and secure lines of communication rely on the technology.
"That's where lasers are really making a difference," she says. "We just take it for granted now."
One of the main obstacles to developing lasers as weapons has been generating enough power for the kinds of laser blasts that battlefield planners have envisioned. But designers recently passed the 100-kilowatt (100,000 watts) benchmark (enough energy to power about six U.S. homes for a month), which was seen as a key milestone for their development. Engineers have improved lens coatings, laser cooling and miniaturized electronics to keep a bigger laser punch from burning up weapons in mid-operation.
So years of research finally have produced lasers that could be effective on the battlefield, with one possible exception — ballistic missile defense — the area of defense in which the notion of using lasers has attracted the most publicity.
Why? Cost is one reason. Defense Secretary Robert Gates last year canceled plans to buy a laser-equipped 747, saving taxpayers $214 million this year. The program was eight years behind schedule and $4 billion over cost. Gates also questioned the practicality of a laser that needed to be within about 80 miles of a missile to knock it down, meaning it would have to fly over hostile anti-aircraft defenses — probably a suicide mission.
"It's one thing to get a laser working aboard something as big as a 747. It's another to field something that makes sense as a weapon," says former Air Force chief scientist Mark Lewis, now at the University of Maryland. That would have been the military's second laser-outfitted plane. The existing "Airborne Laser Testbed" YAL-1 747 remains a research effort rather than a weapon. It's run by defense industry titans Northrup Grumman, Boeing and Lockheed Martin.
This year, the Defense Department's Missile Defense Agency announced that a 100-kilowatt laser aboard the research 747 had shot down Scud missiles in two tests, the first since a weaker laser knocked down smaller Sidewinder missiles in the 1980s.
But Air Force Gen. Norton Schwartz, who called the demonstration "a magnificent technical achievement," said the type of chemical lasers used for the system were too heavy and unreliable for wartime use. Electronic solid-state lasers, an approach pursued by the U.S. Navy, seem more practical, because of their smaller size, power needs, easier cooling and insensitivity to vibrations.
The missile defense systems are still works in progress, but lasers are making gains in other military arenas:
•Last year, a "Laser Avenger" mounted aboard a truck shot down unmanned aerial vehicles in tests at White Sands Missile Range in New Mexico.
•In October, a laser-equipped U.S. Air Force "Advanced Tactical Laser" C-130 airplane burned a hole in a slow-moving vehicle during a test at White Sands.
•The Pentagon's Defense Advanced Research Projects Agency (DARPA) signaled plans last year to develop a plane-mounted 150-kilowatt, 1,650-pound laser to knock down rockets and artillery shells in flight. Tests pointed to success shooting down mortar shells, the U.S. Army said.
•Not a weapon but a weapon tester, the Energy Department's National Ignition Facility is using the world's most powerful laser to simulate hydrogen bomb blasts on nuclear material.
In 2008, a National Research Council Report called for the U.S. Army to speed development of a $470 million "mobile, 100,000-watt solid-state laser weapon system" to knock down mortar shells and rockets by 2018. The 100-kilowatt laser was demonstrated by Northrop in May last year. But it required a tractor-trailer-sized laser, Weinberger notes, not something that a Humvee could carry.
"There are a lot of people spending a lot of money and a lot of time looking for military uses of lasers," Lewis says. "The bottom line of this interest is that they haven't proven themselves yet, but they have overcome a lot of challenges."
Says Imaginary Weapons author Weinberger: "In the military world, one real question is: Why do we need them? What can lasers do that we can't do with bullets and missiles? Given their costs and the fact that they weigh too much and are unreliable, I don't see them as too useful."
Other observers are less kind. Joe Cirincione, author of Bomb Scare: The History and Future of Nuclear Weapons, derided laser weapons as "Flying White Elephants" in a Huffington Post report last year.
"The technical challenges are immense" to make lasers work, Weinberger notes. A 2008 report by the non-profit Institute for Defense Analysis, for example, urged the Pentagon not to rush immature laser technologies into development. And a National Research Council report on Navy lasers last year noted that the Defense Department has investigated such weapons for four decades with little success.
In March, Georgetown University physicist Francis Slakey called some laser technology dangerous in the journal Nature. He argued that improvements in laser enrichment of uranium fuel made it more likely that nations such as Iran would acquire an atomic bomb.
Still, Lewis and others see a military role for lasers.
"Lasers don't do the whole job," says Boeing's Greg Hyslop, a colleague of Rinn's. "But it will complement what we have today." He argues that lasers are faster and more precise than bullets or bombs and can be set to kill or be non-lethal.
Reducing "collateral damage" from bombs killing people around targets has emerged as a laser selling point, Hyslop says. In a speech April 21, 2008, Defense Secretary Gates said, "An unconventional era of warfare requires unconventional thinkers," specifically calling for munitions that reduce the chances of civilian deaths that cost public support for repelling insurgencies.
Lewis says that is "a real argument" for lasers, which theoretically would pinpoint targets in ways that explosives cannot. "I can tell you people in the military are considering very precise (conventional) munitions, with very proscribed blast radius, for just this reason," he says.
Power increases in military laser programs have been a surprise, Lewis adds. The 100,000-watt (or more) laser aboard a 747 used in January packs enough punch to burn a hole in a moving missile in under two minutes.
"I was more skeptical just three years ago of lasers reaching some of the power levels we see now," Lewis says.
But that still leaves the challenge of reducing the weight of a laser weapon, Weinberger says. The Missile Defense Agency's chemical laser weighs more than 175,000 pounds, the National Research Council says. If you visit labs, Weinberger says, "you'll see the 'laser' is something the size of two buildings. You can't fit that onto a rifle barrel."
Says Boeing's Rinn: "All the science and physics are now proven" as far as how lasers work and what they can do. "Really what it is all about is national will and investment in engineering."
Legal restrictions further weigh down the chances of battlefield lasers, Lewis says. "We can kill 'em, but we can't blind 'em," he says, citing war crime rules that declare it illegal to blind enemy troops.
After World War I's experience with mustard gas, blinding soldiers was seen as a war crime, and a 1980 protocol of the Geneva Convention outlaws "blinding laser weapons." The Defense Science Board, a Pentagon science think tank, came to the conclusion two years ago that such policy considerations made fielding lasers as weapons particularly complicated and noted the Defense Department was looking at fewer laser technologies than in the 1990s.
So, lasers seem unlikely to directly replace bullets anytime soon.
"There has to be a practical viable application. Maybe we will be blinding unmanned aerial vehicles in the future, for example," Lewis says. "There is something to be said for a weapon that makes somebody uncomfortable enough to turn aside from whatever they are doing. We could use that, too."
Has it already begun?
In a certain sense, the laser era in the military may already be here.
Defense News reported in 2006 that China had illuminated a U.S. imaging satellite with a laser, potentially damaging the sensitive optics aboard the spacecraft. Donald Kerr, director of the Pentagon's National Reconnaissance Office, later told Reuters "it did not materially damage the U.S. satellite's ability to collect information."
Most likely, the Chinese weren't trying to blind the satellite but were measuring its distance to better define its orbit, concluded astrophysicist Yousaf Butt of the Harvard-Smithsonian Center for Astrophysics.
About 40 "Satellite Laser Ranging" stations worldwide use laser pulses aimed at satellites to time how long it takes the light to return to Earth, which can answer questions about the planet's gravity and reveal satellites' orbits, important to know if you plan to hide activities from spy satellites.
U.S. military satellites probably have shutters to prevent blinding by lasers, says Benn Tannenbaum of the American Association for the Advancement of Science's Center for Science, Technology and Security Policy, but nothing legally prevents anyone from trying.
"Technology always has dual uses," says
Georgetown's Slakey. "At any point where a technology develops and
develops, we are going to see military uses."