As early as today government scientists in the tawny desert of White Sands, N.M., will to try to shoot a bullet out of the sky with a bullet.
They will launch a rocket into the outer reaches of the atmosphere to intercept a mock enemy missile. If all goes as planned, it will slam into the intruder in a collision that symbolizes both the problems and promise of trying to devise a shield against enemy missiles.
Indeed, 15 years and more than $56 billion after President Reagan's gauzy vision of creating a high-tech halo to guard America, the Pentagon is making advances in its quest to create a more modest "star wars" shield.
But it is still years away from being able to deploy a workable system, and scientists may not even know until early next century whether they can develop all of the science needed to build it.
The result is an enduring debate in Washington over the merits of moving ahead with a program that already represents the single biggest expenditure in the Pentagon budget.
To critics, the star wars program represents a technological chimera that will only waste billions of taxpayer dollars. But the Pentagon and supporters on Capitol Hill argue it is something the country can't afford not to develop - particularly in an age when more and more rogue nations are developing nuclear-weapons capabilities.
Nor is the debate confined to the US. Some other nations, notably Japan, are interested in seeing the US develop antimissile technology that they may be able to use in light of growing tensions with North Korea. Russia, meanwhile, reiterated a warning July 27 that if the US continues to pursue a missile-defense system it will be forced to improve its own nuclear capabilities.
"Missile defense is a fool's game you can't win," says Joseph Cirincione, a senior associate at the Carnegie Endowment for International Peace.
For now, the politics is working in favor of star wars. In an early campaign environment with presidential and congressional power hanging in the balance, few politicians want to appear weak on national defense. Thus funding for missile defense has been moving swiftly through Congress. President Clinton signed a missile-defense law last week.
The modern version of star wars is nothing like the futuristic system of space-based lasers and particle beams that Mr. Reagan initially outlined. Today's approach is to use earth-based missiles to protect cities by intercepting and destroying enemy missiles as they come in.
But the technology to do so remains formidable. Engineers have been at a loss to consistently hit incoming missiles. Since 1976, 17 high-altitude interceptions have been attempted; three were successful. At least one of the successes was marred by accusations of test rigging.
"You aren't going to fly on an airplane that's crashed every time but once," says John Pike, head of space policy for the Federation of American Scientists.
The current generation of missile-intercept programs under development is also unable to defeat countermeasures - including "decoys" - any ICBM would be expected to carry. "It isn't like shooting skeet," says Mr. Cirincione.
The Army's THAAD program (theater high-altitude area defense), which gets another shot at glory this week, first came off the drawing board in the early 1990s. It had its first successful hit last month after six misses.
"I think we are feeling a little more comfortable now," says Air Force Brig. Gen. Richard Davis, who helps oversee the missile-defense program. "There are still some issues as we address the entire spectrum of targets we have to look at."
While THAAD is intended to defend against threats at medium range, a much larger interceptor with a range of thousands of miles would be able to create a wider national missile umbrella.
The first such interceptor test isn't scheduled until September, but there's already concern that such a program violates the 1972 Antiballistic Missile Treaty, which includes limits on testing and deploying defensive systems.
"At the moment, the ABM treaty prohibits testing, let alone deployment of a national-defense interceptor," says retired Army Col. Dan Smith, now chief of research at the Center for Defense Information, a Washington-based Pentagon watchdog group.
By June 2000, just as the presidential campaign begins to heat up in earnest, Mr. Clinton will face a deadline of committing to deployment of the national missile-defense system.
Moving ahead with a larger intercept system is estimated to cost as much as $28 billion.
Russian Prime Minister Sergei Stepashin, visiting Washington this week, expressed Moscow's reservations about the antimissile program. President Clinton, for his part, has put some qualifiers on the deployment of a shield. "Any national-missile-defense system we deploy must be operationally effective, cost-effective, and enhance our security," he says.
While any missile umbrella is years away, the need to defend against enemy warheads has taken on more urgency in the wake of recent developments overseas. This includes North Korea's testing of a multistage Taepo Dong missile as well as allegations of China's theft of nuclear secrets from the US.
"There's something of a consensus that we should try to provide some sort of defense," says Steven Kosiak of the Center for Strategic and Budgetary Assessments. "There are still a lot of questions about when and what kind of system" to deploy.
(c) Copyright 1999. The Christian Science Publishing Society