Is This A Good Idea : Science Channel

January 18, 2011

By Patrick J. Kiger

What if the Pentagon had killer satellites equipped with lasers, which enabled ground controllers to pinpoint a target--a ship, a building, perhaps even an individual enemy combatant--and cause it (or him) to vanish without a trace? Should we try to develop such a weapon? Is it even possible?

Considering the vastness and lethality of the arsenal that we already possess, you might wonder why the U.S. ever would need space-based guns firing death rays. After all, according to the Center for Arms Control and Non-Proliferation, the U.S. spends roughly $700 billion a year on its military. China, the nation widely perceived as the biggest potential U.S. rival for global supremacy, spends only about $85 million. According to the Arms Control Association, the U.S. possesses more than 5,000 nuclear warheads, while China has just 240 nukes. The U.S. Navy has 10 aircraft carriers, capable of waging war across the globe; the Chinese Navy doesn't have any.

Nevertheless, Washington Post columnist David Ignatius recently warned that the U.S. may become dangerously vulnerable to China, if the Chinese follow a philosophy espoused by Fudan University defense scholar Dingli Shen, and develop high-tech gadgetry capable of stopping numerically superior U.S. forces in their tracks. Ignatius wrote:

Shen, who teaches at Fudan University, was countering the view of some Chinese analysts that Beijing should embrace the gospel of Alfred Thayer Mahan, the 19th-century American missionary for sea power. Mahan is outdated, he said: With a laser weapon fired from space, "any ship will be burned."

Ignatius explains that Shen's orbiting death-ray example was a "light bulb" moment for him. He warns that the U.S. can't waste a lot of money on aircraft carriers and the like, without risking falling behind in developing the next generation of cutting-edge weapons.

...instead of competing to build ships and tanks, [Shen] says, China will focus on the weapons that can cripple them. Somehow, we need to stop being the suckers when it comes to defense.

This might also come as a revelation to both Shen and Ignatius, but the idea of beaming destruction down on Earth from orbit isn't exactly a cutting-edge concept. During World War II, a group of German scientists actually worked on (extremely) long-range plans for a massive orbiting manned space platform, which would have used mirrors to focus solar energy on Earth cities and burn them like ants under a magnifying glass. (Here's a 1945 Time magazine article on the project.) To achieve the desired destructive effect, the Nazis calculated that they would need a "sun gun" three-and-a-half miles across, which is one reason why the U.S. military intelligence unit that captured the plans quickly consigned them to the archives filled with other preposterous Nazi brainstorms, such as submersible troop-carriers capable of crawling across the bottom of the English Channel.

Okay, but what about an orbital laser, which would bunch multiple wavelengths of visible light into a tightly focused beam? Lasers have been around since the mid-20^th century, and sci-fi movies and TV shows have been depicting them as awe-inspiring weapons of destruction for so long that the idea seems almost mundane. (This 2002 report by the Rand Corporation, a think-tank with longtime ties to the U.S. military and intelligence agencies, discusses the potential of space-based directed energy weapons.)

The reality, though, is that after decades of effort and enthusiastic predictions, laser weaponry is still at the embryonic stage. It wasn't until March 2009 that researchers managed to get an experimental laser gun to transmit 100 kilowatts, the threshold that most experts say is necessary to achieve real destructive power. Some recent experiments with experimental military lasers--such as this February 2010 test in which a laser-equipped Boeing 747 successfully shot down a target missile, and this May 2010 test of a Navy ship-based laser system--have been encouraging. But none of those lasers are anywhere near ready for operational testing, let alone actual combat.

A space-based laser weapon of the sort envisioned by Chinese military theorist Shen, one capable of striking targets on the Earth's surface with precision, still represents a vastly more daunting technical challenge. For one thing, lasers are enormously inefficient--they waste roughly 80 percent of their electrical input as heat--so a space laser capable of generating a powerful-enough beam of concentrated energy to attack a distant target on Earth would require many tons of chemical fuel, or a massive array of solar panels, to generate the needed electricity. The sheer size of that infrastructure, and the difficulty of maintaining it, might make space-based laser satellites extremely vulnerable to sabotage or preemptive attacks.

Additionally, there's the problem of "blooming"--that is, the tendency of a laser to defocus and disperse energy over a wider area as it passes through the atmosphere. That effect would be exacerbated by naturally occurring fog, smoke or dust. And lasers, at least the ones we have now, don't destroy instantly; depending upon their power capability, they require varying amounts of time to cut through a target--an interval that can be increased by almost ridiculously simple countermeasures. As this insightful 2005 article from IEEE Spectrum, an engineering publication, notes:

Vulnerability is increased by the need to keep the laser on target for tens of seconds at least. The target could move in an unpredictable path or simply be covered with a reflective coating or paint, which could increase the time required for a successful kill by a factor of 10 or more. A layer of titanium oxide powder, for instance, could reflect 99.9 percent of the incident laser energy. Even a shallow pool of dyed water would offer serious protection for structures. Since a 20-MW laser boils water at a rate of 10 kg/s, a pool of water about 3 centimeters deep on the flat roof of a two-car garage would protect against 100 seconds of illumination by a space-based laser.

In view of all this, I'd have to say that if the Chinese military decides to follow Shen's advice and spend many, many billions of dollars to develop space-based laser weapons that most likely will never work, I'm all for it. But I think it would be breathtakingly dumb for the U.S. to waste money on developing such weapons, barring some unforeseen research breakthrough. There are a lot of ways that we can get a bigger bang for the buck--not all of them lethal, but that's a whole different subject.

So what do you think? Post your thoughts below.