The Master Spy Who Failed

By Philip Elmer-DeWitt

On Jan. 27, 1950, a balding, bespectacled German-born physicist named Klaus Fuchs walked into London's War Office and confessed to being a spy. For seven years, from 1942 to 1949, Fuchs had systematically funneled high-level secrets about U.S. and British nuclear-weapons research to the U.S.S.R., including plans for the yet unfinished hydrogen bomb.

Fuchs' confession and subsequent trial marked a turning point in the history of the cold war. Evidence supplied in the confession led to the arrest of Julius and Ethel Rosenberg for what J. Edgar Hoover termed "the crime of the century" and prompted President Harry Truman to launch an all-out program to develop the so-called Super Bomb. Two and a half years later, thanks to the determined efforts of Edward Teller and colleagues at the Los Alamos Scientific Laboratory, the U.S. detonated the first thermonuclear device, beating the Soviets to the H-bomb by more than three years.

Fuchs' betrayal of the H-bomb secrets passed into the folklore of the nuclear age. The folklore, however, is false. Fuchs' H-bomb plans were totally misleading, and Truman's rationale for rushing to build the bomb before the Soviets did was on shaky ground. That is the conclusion of an article in the January-February issue of the Bulletin of the Atomic Scientists, one of a series of scholarly works that are rewriting a period of U.S. history still shrouded in mystery and official secrecy. According to Daniel Hirsch and William Mathews, what Fuchs gave the Soviets was an early design of Teller's that turned out to be unworkable. The crucial insight, they say, came after Fuchs had been imprisoned, and it was supplied not by Teller but by his Los Alamos colleague Stanislaw Ulam. Says Hirsch, former director of the nuclear- policy program at the University of California at Santa Cruz: "In many ways, Stan Ulam was the true father of the H-bomb."

The key to the new account is a top-secret history of the H-bomb written by Hans Bethe in 1952 and only recently declassified. According to Bethe, who headed the theoretical-physics division at Los Alamos during World War II, Teller's design began to fall apart shortly after Truman launched his H-bomb program. Teller's idea had been to use the heat of a conventional A-bomb to ignite a separate H-bomb. But Ulam, a brilliant mathematician, made a series of calculations that showed that the amount of tritium fuel required for Teller's bomb was prohibitive and that even when sparked by an A-bomb, it would probably not achieve fusion.

The breakthrough idea was the recognition that the fuel would burn more efficiently if it was compressed before it was heated. According to Bethe, Ulam approached Teller with a two-stage H-bomb design that used the shock waves from an A-bomb to compact the hydrogen and ignite the H-bomb. Teller adapted Ulam's design, using the energy of the A-bomb's radiation rather than the force of its shock waves to achieve the necessary compression. It was a bomb of this design, code named Mike, that exploded on Nov. 1, 1952, on the Pacific island of Elugelab. The island, one mile in diameter, disappeared.

If Fuchs did not give the Soviets the secret of the Teller-Ulam bomb, who did? Hirsch and Mathews suggest that Teller himself may have inadvertently - assisted the Soviets by pushing for an early test blast. The 1952 explosion peppered the atmosphere with a telltale assortment of radioactive debris, including new atomic elements that could have been created only by a compressed fusion reaction. When Hirsch and Mathews asked Bethe if that fallout could have tipped off the Soviets, Bethe instantly said yes. Says Hirsch: "It was as though he had been waiting 35 years for someone to ask him that question."

The Hirsch and Mathews account has received mixed reviews from the surviving members of the Los Alamos team. Carson Mark, who took over for Bethe in 1947, concedes that the U.S. monitored the Soviets' weapons research by examining the fallout from their blasts, but he doubts that the U.S.S.R. could have worked in the other direction, deducing the secret of Mike's construction by studying its debris. Teller and others believe that the late Andrei Sakharov, who built the Soviet H-bomb, was clever enough to have invented the device from scratch, without the help of Fuchs or anyone else.

One participant who welcomes Ulam's heightened status is his widow, Francoise Ulam, who will never forget the day she returned home for lunch to find her husband staring fixedly out the window. "I think I've found the way to make it work," he told her. "Make what work?" "The Super." Teller has partially confirmed his debt to Ulam. After suffering a heart attack in 1979, he dictated an account of the day Ulam walked into his office and said he had a way to make the bomb. Teller, though, heatedly disputes the notion that the key idea was Ulam's. "That is not correct," he says. "I do not want to say what is correct. It is a long and complicated story. Someday I will write it down."

But history may have already been rewritten. The revised account of Ulam's pivotal role appears in several new books, including a biography of Teller by Stanley Blumberg and Louis Panos to be published in February by Scribner's. And it is repeated in detail in the latest revision of the New Encyclopaedia Britannica, due out next month.