Exploring the High-Tech Frontier

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Which does not necessarily mean that it ought to be built. Even if the S.D.I. proves technologically feasible, serious questions would arise as to whether it would really strengthen deterrence, and at what cost. Estimates of the money required start at $60 billion for a rudimentary system that would rely on interceptor rockets. Calculations of the cost of a fully developed laser- or particle-beam system run all the way from $100 billion to a staggering $1 trillion. Such a broad range means that all the figures are fairly wild guesses. Indeed, Cory Coll, leader of an S.D.I. research group at the University of California's Lawrence Livermore National Laboratory, predicts it will be five years before any halfway realistic estimate can be made of the cost of developing X-ray lasers as a warhead-killing weapon.

A go or no-go decision is still years away. Reagan sometimes talks as if he is determined to start on a defensive system no matter what, and some S.D.I. advocates hope to see component tests or even "demonstration shots" of prototype weapons during his second term. That is a dangerous idea, since it would violate a 1972 treaty with the Soviets and could get the U.S. irreversibly dedicated to a Star Wars defense of doubtful feasibility. Nonetheless, the Administration so far has not committed the U.S. officially to anything beyond a research program now expected to cost $26 billion in fiscal years 1985 through 1990. The requested appropriation for fiscal 1986, which starts Oct. 1: $3.7 billion.

Though the outcome of the research program cannot be predicted, the problems being faced and some of the ways in which they might be overcome are reasonably clear. Every proposal for a missile defense system begins with a profile of an enemy nuclear attack. In its roughly 30-minute flight from a silo in Siberia to detonation on top of a Minuteman silo in North Dakota--or above the White House--a Soviet warhead would go through four well-marked stages: 1) Boost. The rocket engines of, say, an SS-18 missile push it up through the atmosphere and into space. 2) Post-boost. On reaching the edge of space five minutes or so after launch, a device known as a bus detaches itself and maneuvers for another five minutes or so, releasing up to ten MIRV (for Multiple Independently Targetable Re-entry Vehicle) warheads at different targets in the U.S. The bus may also release up to 100 decoys, many of them aluminum-foil balloons. 3) Mid-course. The warheads and decoys speed through the emptiness of space for more than ten minutes. 4) Re-entry. The vehicles plunge back into the atmosphere and toward their targets.