In a move intended to start a wave of scientific opposition to the Strategic Defense Initiative (SDI), most physicists at the University of Illinois have signed a statement branding the proposed antimissile system "technically dubious" and refusing to accept funding from the Pentagon's SDI organization.

Physics professors at Illinois, which has the nation's second-largest physics department (after the Massachusetts Institute of Technology) and one of four designated national supercomputing centers, announced their effort yesterday and said similar statements are circulating at other universities and research centers.

The statement was signed by 47 of the university's approximately 60 physics faculty members and by 70 doctoral students. Physics Professor Fred Lamb said those who did not sign were away from campus for the summer and could not be reached immediately. He said he knew of no refusal to sign.

John Kogut, another Illinois physicist, said he recently took the statement to the International Conference on High Energy Physics at the University of California at Berkeley and all of the two dozen U.S. citizens attending signed.

Kogut said copies of the statement or similar statements are circulating at Berkeley, Cornell University, IBM's Thomas J. Watson Research Center at Yorktown Heights, N.Y., and at Fermilab, a premier physics research center outside Chicago.

"Summer is a slow time to get something like this going among university people," Kogut said. "But the ball is rolling and we expect that in the fall the movement will become more coherent."

One of the signatories, who is also the head of Illinois' new federally funded National Center for Supercomputing Applications, took the occasion to say that the most dubious aspect of the concept that critics call "Star Wars" is the kind of computer system it would require, especially its program, or software.

SDI officials have said that their antimissile system would be so complex and would have to operate so fast that it could only be controlled by a computer system much larger and vastly more complex than anything possible with today's state of the art.

They have estimated the hardware would be under the control of a computer program containing roughly 100 million lines of code. Typical home computer programs contain a few hundred lines and highly sophisticated scientific programs contain a hundred thousand lines or so.

"In my experience as a physicist who has written some pretty large computer codes," said Larry Smarr, "there is no way you could produce a code large enough to handle the job and do it perfectly the first time, which is what you would need. I can't imagine any developments in computer technology that would make it possible in the foreseeable future."

Smarr said in an interview that he was giving his personal opinion and was not speaking as head of one of the National Science Foundation's four new national supercomputer centers, established last spring in an effort to catapult the United States ahead of Japan in the race to capture the global computer markets of the future.

The circulated statement reads, in part, "We believe the Star Wars program is technically dubious and politically unwise. Antiballistic missile defense of sufficient reliability to defend the population of the United Sates against a Soviet first strike is not technically feasible in the foreseeable future. A system of more limited capability will only serve to escalate the arms race by encouraging the development of both offensive overkill and an all-out competition in antiballistic missile weapons.

"As working scientists," the statement concludes, "we will not apply for nor accept support from the Strategic Defense Initiative Organization, which funds Star Wars research. We encourage other scientists and technical personnel to join us in this refusal. We hope, together, to persuade the public and the Congress not to support this deeply misguided, dangerous, and enormously expensive program."

The statement was written by a group of physics professors.

"We felt this was needed because it seemed to us that many members of the public are under the impression that this SDI is something the scientific community supports. That just isn't so," said Lamb, who is an associate of the University of Illinois' arms control and disarmament studies program and a spokesman for the group.

Lamb said that although some news accounts have suggested SDI has wide scientific support, the scientists he knows are overwhelmingly against the concept.

Smarr, the supercomputer expert, said he saw two main obstacles to developing the software needed in the SDI.

The first consists of the inevitable errors, or bugs, that creep into every new, complex program. Debugging efforts find many errors, but only repeated use of the program under realistic conditions exposes them all.

"Eventually, you can find these errors," Smarr said, "but you don't have that chance with Star Wars. It has to work the first time it's tried in the real world."

Even if all such bugs could be eliminated, Smarr said, the system would be doomed to a second class of errors: the failure to anticipate some new weapon or battle tactic that the Soviets might develop, especially if they knew the antimissile system's limits.

"If the Soviets come up with just one special trick to spoof the system and our people didn't happen to design the system to cope with that, it won't work," Smarr said. "It's going to be a Maginot line in space."