Star Wars Junior: Will It Fly?
At 5 a.m. on Dec. 13, a white, pencil-thin missile lifted off flawlessly from a mobile launcher into the starry skies above White Sands Missile Range in New Mexico. The Theater High-Altitude Area Defense (THAAD) payload separated from its booster stage, shed the shrouds protecting its supersensitive infrared sensor, and locked on target--a dummy ballistic missile. Then...bust. A software glitch sent the THAAD in the wrong direction. The 20-foot-long missile corrected course, but too late. Before it could intercept and kill the target, the THAAD ran out of fuel.
The encouraging launch and its disappointing outcome provide an apt metaphor for the current state of the nation's ballistic-missile defense program. Many of the program's new gizmos work well. The Pentagon has made great strides in technology, from new thruster systems to MADCAP data-processing techniques. (It stands for "mosaic array data compression and processing.") But the experts haven't worked out all the kinks in missile defense. "It's an extremely difficult technical problem," says U.S. Air Force Secretary Sheila E. Widnall.
ROGUE NUKES. It's a tricky political problem, too, now that former Senator Bob Dole wants to make the development of a scaled-back Star Wars system a cornerstone of his Presidential campaign. THAAD, a system designed to protect troops from short-range missiles in a war theater, is a junior version of the big kahuna Dole wants: a scheme to protect the entire U.S. from intercontinental ballistic missiles. Spurred by focus groups of voters who are shocked to learn the U.S. has no defensive umbrella against a nuclear attack, Republicans hope to use the issue to make President Clinton look weak on defense. Democrats agree that there's a long-term threat and a need for such a system. But they want to focus spending now on the less ambitious goal of protecting soldiers from attacks by short-range, Scud-like missiles.
Beyond the question of what Washington should do is the question of what the U.S. can do. Unlike Ronald Reagan's Star Wars vision of a shield against thousands of incoming Soviet missiles, which may be technologically impossible, the goal of a national missile defense today is to thwart a handful of nukes launched by a rogue state such as North Korea or Iran. The Congressional Budget Office estimates the Pentagon plan for such a limited missile defense would cost $6 billion over the next five years. Even opponents agree the Pentagon plan is feasible. "I don't see any reason why they shouldn't eventually be able to hit targets," says critic Theodore Postol, professor of science, technology, and national security policy at the Massachusetts Institute of Technology.
Any national system would be far more sophisticated than past programs, such as Sentinel and Safeguard, that relied on nuclear-tipped warheads to obliterate anything that threatened Minuteman silos in North Dakota. And the system would be far more powerful than the Patriot missile. Military planners today opt for more precise "hit-to-kill" interceptors, which collide with their targets to knock them out.
Mother Nature favors the aggressor. Three-quarters of an ICBM's half-hour flight is above the atmosphere. This midcourse phase poses the greatest natural obstacles to efforts to detect and track an enemy missile. The cold temperatures above the atmosphere make it harder for heat-seeking infrared sensors to discriminate among warheads, decoys, and booster fragments, whose different masses and densities give them far different temperatures after they reenter the atmosphere. Likewise, it's easier for traditional radar to separate targets from decoys and fragments after atmospheric reentry, where the heavier warheads continue to speed toward their target while everything else slows down and tumbles. Advances in radar and infrared technology, however, have gone a long way toward overcoming these hurdles.
One example of an important technological advance is X-band solid-state radar. By operating in the X band of the radio spectrum--a spot around 10,000 megahertz that's well above ultrahigh frequencies that TV stations employ--the radar can use a narrow beam that offers better resolution than older radar, which operates at lower frequencies. X-band radar already is being used in theater-missile defense tests to help track targets.
For a national system, the theater version would have to be upgraded in size and sensitivity to compensate for the increased distances covered and the speed of the target. ICBMs, with a range of 3,720 miles and speed of 5 miles per second, travel about 10 times as far as theater missiles and 4 times faster. But the basic radar solution is the same. What's needed is "not a scientific breakthrough, but just good old engineering," says Robert M. Stein, a Raytheon vice-president who oversees advanced systems activities.
Advances in infrared sensors--which would be located both in low-earth orbit and in higher orbits at fixed points over the globe--can also help detect the real targets. The long-wave sensors now being tested in the Pentagon's Midcourse Space Experiment are capable of picking up tiny heat differences even in the cold environment above the atmosphere. The sensors are chilled by cryocoolers--tiny refrigerators--to 10 degrees Kelvin, or 18F above absolute zero. "You want your detector to be cooler than the object you're looking at," says Frank R. Cartier, manager of TRW Inc.'s surveillance programs directorate. "Otherwise, you're detecting information off your noisy detector."
Progress has been made, as well, in areas beyond detection and tracking. Interceptor missiles are smaller, smarter, and nimbler than ever before. New thruster technology makes it easier to correct course based on the updated data flow from the sensors. But technology may have progressed faster than humans can handle it.
Indeed, of the challenges remaining, helping humans cope with all the new data is a major one. Pentagon officials are starting to grapple with the need to process the overwhelming amount of useful information from radars and sensors, and to fuse "pictures" collected at different wavelengths into one super-image. MIT's Lincoln Laboratory and Texas Instruments are looking at possible algorithms to solve the vexing problem.
Even if the system for midcourse-intercept problems were solved, however, experts say the confidence level in the ground-based system would be barely above 90%. There would be no guarantee that deployment could really stop Pyongyang from incinerating Los Angeles or Chicago. Improving the confidence level to, say, 99.9% would require more layers of defense and billions of dollars above the $39 billion spent since 1984.
Such a system would violate the 1972 ABM Treaty, however. And some of the solutions are decades away from reality. Some Star Warriors would just upgrade the Navy's sophisticated Aegis cruisers and station them offshore, where they could quickly reach missiles from a Libya or North Korea. But the Navy might balk until a solid propellant is created. Solid propellants are less volatile and toxic than liquid propellants.
Another possibility is space-based lasers. Operating above the atmosphere, their beams wouldn't be degraded by air turbulence--a force that could undermine lasers based on planes. But space-based lasers aren't panaceas. Like a magnifying glass on a piece of paper, lasers emit a steady stream of light to burn through a missile's thin metal skin. If the target spins, the laser would have to be enormously powerful to destroy it.
LEAKY? Gregory H. Canavan, a senior scientist at Los Alamos National Laboratory, envisions a laser mirror 100 times the size of the Hubble Space Telescope's huge 4-meter mirror. Canavan, who has been trying to put a laser in orbit for 25 years, thinks it's still 20 years off. "The deployment date of the darn thing always seems to recede one year per year," he sighs.
Will taxpayers wait--and be willing to shell out billions more? A $6 billion ground-based or sea-based system might seem a reasonable option to many, but it won't be perfect. It's being sold as a shield, but it would leak, allowing some missiles to get through. And the CBO estimates that a more robust layered system with space-based gadgets could cost as much as $60 billion through 2010. Some experts doubt voters will want to buy such expensive protection against such a remote threat. "I'm not sure the country will be willing to commit the resources needed," says MIT's Postol. If he's right, despite all the progress made, the drive for a national security blanket, like the THAAD test, could run out of gas.