The Making of the Atomic Bomb

full of brilliant ideas.

Houtermans had taken a Ph.D. in experimental physics at Gottingen but was strong in theory. One of his brilliant ideas, developed in the late 1920s at the University of Berlin with a visiting British astronomer, Robert Atkinson, concerned the production of energy in stars. Atkinson was familiar with recent estimates by his older colleague Arthur Eddington that the sun and other stars burn at temperatures of 10 million and more degrees and have life spans of billions of years — a prodigious and unexplained expenditure of energy. On a walking tour near Gottingen in the summer of 1927 the two men had wondered if nuclear transformations of the sort Rutherford was producing at the Cavendish might account for the enduring stellar fires. They quickly worked out a basic theory, as Hans Bethe later described it, “that at the high temperatures in the interior of a star, the nuclei in the star could penetrate into other nuclei and cause nuclear reactions, releasing energy.” The energy would be released when hot (and therefore fast-moving) hydrogen nuclei collided with enough force to overcome their respective electrical barriers and fused together, making helium nuclei and giving up binding energy in the process. With George Gamow, Houtermans and Atkinson later named these events thermonuclear reactions because they proceeded at such high temperatures.

In 1933 Houtermans emigrated to the Soviet Union, “but fell victim,” writes Frisch, “to one of Stalin's purges and spent a couple of years in prison; his wife with two small children managed to escape and get to the U.S.A. When Hitler made his temporary pact with Stalin in 1939 it included an exchange of prisoners, and Houtermans was handed back to the Gestapo.” Max von Laue, whom Frisch celebrates as “one of the few German scientists with the prestige and courage to stand up against the Nazis,” managed to free Houtermans and arranged for him to work with a wealthy German inventor, Baron Manfred von Ardenne, who had studied physics and who maintained a private laboratory in Lichterfelde, outside Berlin. Von Ardenne was pursuing uranium research independently of Heisenberg and the War Office; to raise funds for the work he had approached the German Post Office, which commanded a large and largely unused budget for research. The Minister of Posts, imagining himself handing Hitler the decisive secret weapon of the war, had funded the building of a million-volt Van de GraafF and two cyclotrons, all under construction in 1941. Until they came on line Houtermans turned his attention to theory.

By August he had independently worked out all the basic ideas necessary to a bomb. He discussed them in a thirty-nine-page report, “On the question of unleashing chain reactions,” that considered fast-neutron chain reactions, critical mass, U235, isotope separation and element 94. Houtermans emphasized making 94. “Every neutron which, instead of fissioning uranium-235, is captured by uranium-238,” he wrote, “creates in this way a new nucleus, fissionable by thermal neutrons.” He discussed his ideas privately with von Weizsacker and Heisenberg, but he saw to it that the Post Office kept his report in its safe secure from War Office eyes. He had learned to cooperate for survival in the Soviet Union, where the NKVD — the KGB of its day — had knocked out all his teeth and kept him in solitary confinement for months. But in Germany as in the USSR he withheld as much information as he dared. His private endorsement of 94, to be transmuted by chain reaction from natural uranium, probably contributed to the neglect of isotope separation in Germany. After the summer of 1941 the German bomb program depended entirely on uranium and Vemork heavy water.

The British, at least, knew where they were going. Tizard was skeptical of the MAUD Report and doubted that a bomb could be produced before the end of the war. Lindemann — he was Lord Cherwell now, a baron, courtesy of his friend the P.M. — did not. Cherwell had followed the MAUD work carefully. He respected Thomson; Simon was an old friend; Peierls had read his grunts correctly after all. He trusted their judgment and set to work to reduce the lengthy report to a memorandum for Churchill. Churchill liked his documents held to half a page. So important was this one that Cherwell allowed it to run on for two and a half pages. He thought research should continue for six months and then face further review. He thought an isotope-separation plant should be erected not in the United States but in England — despite manpower shortages and the risk of German bombing — or “at worst” in Canada. In that conclusion he differed from the MAUD Committee. “The reasons in favor [of an English location],” he wrote, “are the better chance of maintaining secrecy… but above all the fact that whoever possesses such a plant should be able to dictate terms to the rest of the world. However much I may trust my neighbor and depend on him, I am very much averse to putting myself completely at his mercy. I would, therefore, not press the Americans to undertake this work.” His summation narrowed the odds but decisively raised the stakes:

People who are working on these problems consider the odds are ten to one on success within two years. I would not bet more than two to one against or even money. But I am quite clear that we must go forward. It would be unforgivable if we let the Germans defeat us in war or reverse the verdict after they had been defeated.

Churchill received Cherwell's recommendation on August 27. Three days later he minuted his military advisers, alluding ironically to the effects of the Blitz: “Although personally I am quite content with the existing explosives, I feel we must not stand in the path of improvement, and I therefore think that action should be taken in the sense proposed by Lord Cherwell.”

The British chiefs of staff concurred on September 3.

Mark Oliphant helped goad the American program over the top. “If Congress knew the true history of the atomic energy project,” Leo Szilard said modestly after the war, “I have no doubt but that it would create a special medal to be given to meddling foreigners for distinguished services, and Dr. Oliphant would be the first to receive one.” Conant in his 1943 secret history thought the “most important” reason the program changed direction in the autumn of 1941 was that “the all-out advocates of a head-on attack on the uranium problem had become more vocal and determined” and mentioned Oliphant's influence first of all.

Oliphant flew to the United States in late August — he considered the Pan-American Clipper through Lisbon too slow and usually traveled by unheated bomber — to work with his NDRC counterparts on radar. But he was also charged with inquiring why the United States was ignoring the MAUD Committee's findings. “The minutes and reports… had been sent to Lyman Briggs… and we were puzzled to receive virtually no com- ment… I called on Briggs in Washington, only to find that this inarticulate and unimpressive man had put the reports in his safe and had not shown them to members of his Committee.” Oliphant was “amazed and distressed.”

He met then with the Uranium Committee. Samuel K. Allison was a new committee member, a talented experimentalist, a protege of Arthur Compton at the University of Chicago. Oliphant “came to a meeting,” Allison recalls, “.. and said 'bomb' in no uncertain terms. He told us we must concentrate every effort on the bomb and said we had no right to work on power plants or anything but the bomb. The bomb would cost twenty-five million dollars, he said, and Britain didn't have the money or the manpower, so it was up to us.” Allison was surprised. Briggs had kept the committee in the dark. “I thought we were making a power source for submarines.”

In desperation Oliphant reached out to the most effective champion he knew in the United States. He wired Ernest Lawrence: “I'll even fly from Washington to meet at a convenient time in Berkeley.” At the beginning of September he did.

Lawrence drove Oliphant up the hill behind the Berkeley campus to the site of the 184-inch cyclotron where they could talk without being overheard. Oliphant rehearsed the MAUD Report, which Lawrence had not yet seen. Lawrence in turn proclaimed the possibility of electromagnetic separation of U235 in converted cyclotrons and the virtues of pluto-nium. “How much I still admire the way in which things are done in your laboratory,” Oliphant would write him after their meeting. “I feel quite sure that in your hands the uranium question will receive proper and complete consideration.” Back in his office Lawrence called Bush and Conant and arranged for Oliphant to see them. From Oliphant he collected a written summary of the secret British report.

In Washington Conant took Oliphant to dinner and listened with interest. Bush met him in New York and gave him a barely courteous twenty minutes. Neither administrator admitted to knowledge of the MAUD Report. “Gossip among nuclear physicists on forbidden subjects,” Conant characterizes Oliphant's peregrinations in his secret history.

Oliphant also stopped by to talk to Fermi. He found the Italian laureate more cautious than ever, “non- committal about the fast-neutron bomb and not altogether happy about the Bohr-Wheeler theory of fission.”

Before or after his meetings in Washington and New York Oliphant visited William D. Coolidge, the temporary chairman who produced the second NAS report, at General Electric in Schenectady. That visit at least stirred something like indignation. Coolidge immediately wrote Jewett of Oliphant's news, emphasizing for pure U235 “that the chain reaction in this case would take place thru the direct action of fast neutrons…