Shooting for the Stars

By William R. Doerner.

To its supporters, chief among them Ronald Reagan, the notion of a space- based missile defense system holds out the promise of eventually ending the awesome threat posed by the world's nuclear arsenals. To its critics, the idea could worsen the threat by ending any real hope for lasting arms-control agreements and by aborting the work of Soviet and American negotiators meeting in Geneva this week. But to many scientists who are responsible for the technology of the concept rather than its policy implications, Reagan's Strategic Defense Initiative, commonly known as Star Wars, is still little more than, well, pie in the sky.

The idea of being able to zap enemy missiles from the heavens is not appreciably closer to being translated into hardware than it was when Reagan first proposed the SDI nearly two years ago, despite important breakthroughs in microchip and other crucial technology. A report by the congressional Office of Technology Assessment declared the prospect of an effective missile & defense "so remote that it should not serve as the basis for public expectations or national policy." But the concept does have its well-placed supporters, including George Keyworth, the President's science adviser, and Robert Jastrow, founder of the Goddard Institute for Space Studies in New York City.

The SDI stems from the desire to protect the U.S. from a Soviet nuclear strike by relying on something more than the Kremlin's fear of American retaliation. Achieving such protection means finding a way to intercept Soviet intercontinental ballistic missiles (ICBMs) in flight. To accomplish this, scientists have suggested adapting various superadvanced technologies involving lasers, particle beams or projectiles that can be aimed through space at moving objects.

Named as the project's overseer was Air Force Lieut. General James Abrahamson, a tall, slim officer who made his name by helping to develop the lean and mean F-16 fighter jet in the 1970s. Abrahamson's office, in a drab rented building two blocks from the White House, is dominated by a large conference table and a blackboard on which he constantly chalks diagrams. Budgeted at $1.4 billion in the current year, the SDI is scheduled to spend some $26 billion over five years. There are fewer than 100 full-time staffers; most of the funds go for research projects assigned to private firms or federal facilities. So far, Abrahamson has spent much of his time soliciting bids from contractors for systems that could "detect, identify, discriminate, intercept and destroy ballistic missiles." Ten aerospace-industry study teams have been awarded $1 million each to come up with "architecture" studies describing more precisely what the military is seeking.

Many of the most basic decisions about Star Wars hardware have yet to be made. Should the lasers or other beams be projected from a satellite (see chart)? Or should the system be based on the ground, with beams bounced off reflecting mirrors in space? Would a system be strategically acceptable if even one of the 5,800 Soviet nuclear warheads were to penetrate it? "It's too early to say," Abrahamson answers when asked such specific questions. "That's what the research program is supposed to tell us. It may take decades, and we can't now even imagine some of the technology we'll be using."

One key unresolved issue is what type of Darth Vader death ray will prove most effective for missile dueling. Laser technology is probably the furthest advanced, but it is a prodigious consumer of energy: by some critics' estimates, any space-based system would require launching enough fuel tanks to generate the equivalent of 60% of total U.S. electricity production. Also being considered are neutral-particle beams, tiny uncharged bits of matter that can travel at 60,000 miles per second. A third possibility is so- called rail guns--giant space-based weapons capable of firing small pellets at up to 15 miles per second. The Soviet Union has already tested an antisatellite system, using interceptor satellites and possibly lasers, that could be the starting point for a space-based missile defense of its own. Experts say the Soviets are about abreast of the U.S. in producing high-energy lasers and ahead in the power sources necessary to run them. But the U.S. is believed to hold a substantial lead in computer technology and sensors.

Abrahamson says the U.S. goal will be to develop a "layered defense," one that is designed to take out enemy nukes during each phase of their flight. The most critical of these is the boost phase, the three- to five-minute launch period when rocket engines propel the missile out of its silo and into space. A strike during this period could take out up to ten warheads while they were still vulnerably clustered atop the ICBM. Says Abrahamson: "That's where the big payoff is."

After the first few minutes, the missile ejects a core element called a bus, which carries the warheads along with decoys. This phase, in which more and more of the missile's elements enter different trajectories, presents a much more difficult target for a laser or particle-beam defense system. Only after they re-enter the atmosphere, and most of the decoys burn, is there one last chance to shoot the warheads down by using ground-based defenses.

The possibility of hitting a warhead in this final phase of flight was demonstrated last summer when Army researchers scored a major breakthrough in an experiment known as Homing Overlay. Using a missile with an infrared sensor, they successfully intercepted an incoming Minuteman missile posing as a Soviet attacker. "That's about ten times as complicated as hitting a bullet with a bullet," says Abrahamson. "Just incredible." Considering the distance that still yawns between SDI as idea and anything approaching reality, the incredible will have to become a regular occurrence at the Star Wars office.

With reporting by Bruce van Voorst/Washington