`Star wars' under the gun. Cost, arms control, and feasibility are the key factors

SDI appears to be in serious trouble. As President Reagan keeps the door open on the latest Soviet arms proposal -- and prods Soviet leader Mikhail Gorbachev to another summit meeting -- pressures are mounting in Congress and the American scientific community to curtail spending for ``star wars,'' as his Strategic Defense Initiative is popularly called.

More than 1,600 scientists in major government and industrial laboratories, many working on SDI research, petitioned lawmakers Thursday to slow the growth of funding for the antimissile defense program, warning that uncontrolled growth of spending could escalate the arms race.

The goal of developing a way to render nuclear weapons obsolete ``is not feasible in the foreseeable future,'' the scientists and engineers said in an open letter to the Senate. ``The more limited goal of developing partial defenses against ballistic missiles does not fundamentally alter the current policy of deterrence, yet it represents a significant escalation of the arms race and runs the serious risk of jeopardizing existing arms control treaties and future negotiations,'' they added.

The scientists' letter was presented at a news conference sponsored by two senators who have forged a coalition of 48 senators seeking a cut in the President's SDI request for 1987. To the administration's dismay, Orrin Hatch, conservative Republican from Utah, recently joined the bipartisan coalition.

Last year the administration asked for a total of $4.17 billion in spending on SDI by the Pentagon and the Energy Department. Congress approved roughly $3.1 billion. This year the administration is asking for $5.4 billion, including $4.8 billion for the Pentagon.

Slashing Mr. Reagan's budget request would be tantamount to derailing SDI, Pentagon officials say, inasmuch as the President wants to move toward a development decision by the 1990s. But the 48 senators have urged the Senate Armed Services Committee to hold the Pentagon's SDI budget at about $3 billion. If it doesn't, the senators hope that an amendment offered on the Senate floor would get enough support for passage. In the House, funding for SDI is expected to be not much higher than this year's level.

Growing opposition in Congress and the scientific community to accelerated funding for SDI bears on the whole issue of arms control. It comes at a time when the Soviets, too, are pressing for constraints on the US defense program.

The Soviet Union's latest arms proposal calls for reductions in offensive nuclear weapons in return for an extension of the Anti-Ballistic Missile Treaty, which restricts SDI development. Moscow would also like to tighten the now-ambiguous treaty definitions of such terms as ``development'' and ``component.''

Some administration officials, including Defense Secretary Caspar W. Weinberger, have criticized the Soviet proposal. But in general the administration has adopted a ``wait and see'' attitude while the offer is being studied. The President has said he is encouraged by the movement in the Geneva arms talks.

SDI has swirled in controversy ever since the President launched it. He is pushing research on SDI technologies to decide in the early 1990s whether to deploy a space-based defense against ballistic-missile attack.

But the persisting budget deficits and the Gramm-Rudman restrictions have engendered concern about the financial costs of the program. Congress has appropriated $5.5 billion for research since 1984. And even if a defense system is deployed, say critics, it would cost as much as $200 billion annually to maintain it.

The feasibility of ``star wars'' as a foolproof population defense is also questioned. Moreover, the Challenger disaster and other recent failures of US rocket launches have intensified concern about going ahead at a swift pace with a defense program that is dependent on space-based monitoring equipment.

J. Carson Mark, former head of the nuclear weapons design at the Los Alamos lab, said Thursday that SDI is certain to prompt efforts by the Soviets to counter it. ``It is almost certainly a much simpler technical task to counter an SDI system than to establish a fault-free system in the first place,'' he said. So he added, the status quo would remain ``on a more edgy level.''

The scientists and lawmakers do not ask that SDI research be stopped but simply kept at a realistic level. Since ``the time before SDI increases our security will be decades, if ever,'' said R. W. Wilson, head of radio physics research at AT&T Bell Labs and a Nobel Prize winner, ``it would be foolish for us to devote a large effort to SDI.'' Except for political purposes, he said, it is not usually useful to undertake large demonstrations early in the research leading to a new development.

Sen. Daniel J. Evans (R) of Washington and Sen. J. Bennett Johnston (D) of Louisiana, who put together the Senate coalition, stressed that the US must proceed with a ``healthy'' but precipitously paced defense research program.