Day-long symposium examines SDIBy Katie Schwarz
No attainable ballistic missile defense can remove the threat of nuclear devastation, but an imperfect shield may reduce that threat, said defense scholar Ashton Carter of Harvard University Saturday at the morning session of a day-long symposium on the Strategic Defense Initiative (SDI).
Carter spoke along with Alexander Flax of the Institute for Defense Analysis, Gerold Yonas of the SDI Office and Richard Garwin of IBM.
The speakers discussed the history and future prospects of anti-ballistic missile (ABM) technology in the morning session of the conference, chaired by Provost John M. Deutch '61.
Approximately 500 faculty, scientists and students filled 10-250 for the symposium, which was sponsored by the Office of the Provost and the MIT Defense and Arms Control Studies Program.
Carter distinguished between two perceptions of SDI. "Star Wars I" was the belief in the possibility of an impenetrable defense which would remove the Soviet capability to do lethal damage to the United States. "Star Wars II" was the expectation that the system would be imperfect but nevertheless worthwhile.
"Star Wars I" has an "ignorably remote" chance of success, Carter said. This does not rule outballistic missile defense's role in national security, he said. A "Star Wars II" system may diminish the "menu" of possible Soviet methods of attack by making some of them too expensive or uncertain, he explained.
The ability of SDI to overcome offensive countermeasures must be measured against an "evolving" level of technology, not against the "static standard" of pre-ABM treaty technology, Carter cautioned. A conflict of "Strategic Defense Initiative versus Strategic Offense Initiative" could appear as each side escalated defensive measures and offensive countermeasures.
The "layering principle," which asserts that defense can be made as nearly perfect as desired by adding more and more stages, is incorrect, Carter said. The effectiveness of each layer depends on the effectiveness of previous layers. The probabilities for a missile to pass through the different layers are not independent and cannot be compounded, he explained. "If layer one collapses, you're screwed in layer two."
Carter was uncomfortable with the "visibility and religious fervor" accompanying SDI. The emphasis SDI has received is "not the usual way we do business" and "doesn't seem responsible," he added.
Yonas emphasized that current SDI research is "driven" by the need to overcome possible countermeasures.
Sensors, data collection and data processing are the most important research efforts because "you can't intercept them if you can't find them," he said. The "distributed" software system -- one with many independent parts -- that SDI needs is widely applicable, he said.
Research in this area would take place even without SDI, he added.
Other areas of emphasis include excimer lasers, neutral particle beams and adaptive optics.
SDI's goals as "crisis stability" and "arms race stability" as well as a greater emphasis on defense rather than offense in the arms race, according to Yonas. SDI can achieve these goals, he said, because the changes in offense that the Soviets would need to make to overcome an SDI defense might be too difficult or expensive.
Predictions of SDI's impossibility are premature, Yonas said. His office aims to "carry out a research program ... as a basis for a decision in the early 1990s."
There are so many possible countermeasures to SDI that the program is not worthwhile, Garwin claimed. A variety of countermeasures that offensive missiles could use to "destroy, bypass or overwhelm" the defense are feasible.
For example, he said, Intercontinental Ballistic Missiles could jitter their flame in the boost phase so they could not be tracked as easily, be protected from the damaging heat of lasers by screens or cooling, or hide from defensive sensors with screens or decoys.
In a question-and-answer period following the discussion, Yonas criticized Garwin's arguments as unrealistic. "We're finding that a lot of these back-of-the-envelope cartoon countermeasures are very hard to engineer," he said.
SDI impedes arms control, Garwin also said. Any defense will be imperfect, so we must "recognize that we're going to be relying on deterrence through retaliation for a long time."
Only a thousand nuclear weapons on each side, much fewer than the current stockpiles, are really needed for deterrence, Garwin continued. But SDI blocks efforts to reduce them to this level, he said.
Despite SDI's flaws, Garwin endorsed research at the rate of $1.5 billion per year to keep up with the Soviets and to "find out whether the President's dream [of perfect defense] is feasible."
Research on intercepting and destroying ballistic missiles has been going on since the Army's Nike Zeus and Nike X programs of the early 1960s, Flax said.
The United States feared that the Soviet Union might be working on similar systems as this technology developed, Flax said. Research proceeded under the Sentinel and Safeguard programs until the signing of the 1972 ABM treaty, he continued.
"Research and development went forward in both the Soviet Union and the United States," although Safeguard was phased out and implementation was curtailed by the treaty, Flax said. There has been less research on countermeasures because the treaty reduces the emphasis on offense, he noted.
"The issues of the current debate [over SDI] don't differ in many particulars" from debates over earlier ABM systems, Flax concluded, citing the question of whether new technology would improve the "cost exchange ratio" -- the relative costs of offense and defense.
Another important question, Flax added, is whether any ballistic missile defense could overcome the "offense-dominated" nature of the current doctrine of mutually assured destruction (MAD). MAD is based upon the belief that nuclear war is forestalled by each side's knowledge that the other can retaliate decisively to a first strike.
Some say "Star Wars" would deter attacks by making them less certain of success, but others claim it would only encourage attempts to defeat it with even greater offensive strength, he explained.