Physics Body Concedes Mistakes in Study of Missile Defense

The world’s largest body of physicists admitted on Monday that a report it had issued seven months ago contained errors that downplayed the effectiveness of a novel plan for shooting down missiles.

The American Physical Society published the 54-page report in February. It assessed the overall feasibility of thwarting missile strikes and concluded that a proposal that the United States use drones to shoot down North Korean missiles faced “very difficult challenges.” The group sent the report to Congress and officials in the Biden administration as part of the society’s long history of providing guidance on cutting-edge weapons to defense policy decision makers.

Three months later, in May, the group pulled the document from its website, saying in an online note that the report was under review by its authors and would be “re-posted when available.” The note gave no reason for the withdrawal.

But the scientists who proposed the drone idea say the reason was errors in the society’s technical analysis of the concept, which the society acknowledged on its website Monday but has yet to detail or explain.

“The whole thing is outrageous,” said Richard L. Garwin, the lead scientist behind the proposal. Dr. Garwin, 94, has advised the U.S. government on issues of national security for more than a half century. He also wields outsize influence in the scientific community because he’s credited with designing — at age 23 in 1951 — the world’s first hydrogen bomb.

He and the other proponent of the drone idea say they want Washington officials to have an impartial assessment of the plan as they consider how to improve the nation’s defenses against enemy missiles.

“It’s a potential system for the defense of the United States, and these people are trying to stop it,” said Theodore A. Postol, the other scientist and an emeritus professor of science and national security at the Massachusetts Institute of Technology.

A group of 13 physicists and engineers wrote the February report. Its chairman was Frederick K. Lamb of the University of Illinois. The co-chairs were James D. Wells of the University of Michigan and Laura Grego of M.I.T. and the Union of Concerned Scientists. The private group, based in Cambridge, Mass., has often faulted antimissile defense as futile and destabilizing.

Academic and private groups have long vetted claims of breakthroughs in destroying enemy warheads fired from the earth’s far side. The task, one of the hardest in modern warfare, is likened to hitting a bullet with a bullet.Members of the American Physical Society have repeatedly caught the Pentagon in errors, exaggerations and what appear to be outright deceptions.

Now, the physical society has been caught in its own error. It says the episode is a first in its 123-year history.

Dr. Garwin and Dr. Postol’s antimissile plan zeros in on destroying North Korean missiles fired at the United States. After Pyongyang achieved a run of successful flight tests in 2017, American intelligence agencies described its intercontinental ballistic missiles and their nuclear warheads as an emerging threat.

According to the plan, American drones would loiter over the Sea of Japan. If North Korea began a nuclear attack, the drones would fire rocket interceptors that would track the fiery exhaust of the rising missiles and annihilate them.

If feasible, the idea is seen as superior to the traditional missile defense method — shattering a missile’s incoming warheads as they race toward their targets. Experts agree that rising missiles are slower, easier to track and far more vulnerable to attack.

In 2004, the Bush administration began deploying, in Alaska and California, a system of interceptor missiles that has about a half-hour to track long-range warheads fired from North Korea. Even so, top experts say it has major shortcomings.

By contrast, the drone interceptors would linger relatively close to enemy launchers. Dr. Garwin and Dr. Postol detailed their plan in 2017 and 2018 studies, prompting the Trump administration to examine the idea as a possible way to thwart the new generation of more threatening North Korean missiles.

In 2020, the physical society began its own antimissile study. It looked at the feasibility over the next 15 years of both the old and new approaches, including Dr. Garwin and Dr. Postol’s. It released its report in February.

The main error uncovered by Dr. Garwin and Dr. Postol in the society’s report centers on the speed of their proposed interceptor rockets and thus how far they would have to fly. The report’s diagram shows the carrier drones as having to loiter over North Korea’s mainland or a narrow strip of its coastal waters in order to knock out missiles fired at Boston, New York or Washington. In such locations, the drones could be shot down.

But the two scientists found that the study group had used the wrong interceptor speed — less than 2.5 miles per second instead of the faster pace of more than 3.1 miles per second. That error might seem small, but the military upshot was not. For an interceptor flight of 195 seconds, the baseline, the correct number was seen as moving the drones more than 100 miles farther out to sea.

“It puts you deep inside the Sea of Japan, where you can loiter and take aim at your leisure,” Dr. Postol said. “Theirs puts you into an area where you can’t operate.”

Soon after the report’s February release, Dr. Garwin and Dr. Postol began exchanging emails with the report’s authors, which The Times has reviewed. In them, the authors admit to mistakes and suggest corrections.

Frances Hellman, a physicist at the University of California, Berkeley, who is president of the physical society, said that in late May and early June, it had privately notified key recipients aboutproblems with the report, including staff members at the National Security Council and the Department of Defense, as well as House and Senate armed services subcommittees.

But making public a corrected version of the report, she added, “may take a year” from the time of its publication.

“We take the integrity of our reports extremely seriously,” Dr. Hellman said in an interview. But removing the errors, she said, is inevitably a slow process because it involves dozens of experts and society officials. “They want it to happen overnight,” she said of Dr. Garwin and Dr. Postol.

Dr. Lamb, the report committee’s chairman, said one snag in the revision was that the study group’s members are busy people who “committed time” to the report. “Now we’re in overtime,” he said. Dr. Lamb added that the job required enormous care. “The worst possible thing,” he said, “is to try to correct something and make another mistake.”

Dr. Hellman, the society’s president, said that the group was seeking ways to better handle such situations in the future.

The long current delay “is not dissimilar to the time it takes to correct a scientific paper,” Dr. Hellman added. “We need to be sure we have the science correct. This argues for more care, not less.”