released 01 jun 09 / last mod 01 jun 09 / greg goebel / public domain
* By early 1940, Allied physicists were increasingly convinced that an atomic bomb was at leat possible in principle. The British government became surprisingly enthusiastic, while the American government continued to waffle on the matter. In the meantime, both the Germans and Japanese conducted preliminary investigations on the prospects for a nuclear weapon.
* While work on atomic power went on in the US and Germany, another effort along such lines was taking place in Britain. Otto Frisch, nervous about Hitler's warmongering, had gone to the UK from Copenhagen in the summer of 1939 to talk about employment there, only to find his bridge back home burned with the outbreak of war. His friends had to arrange storage of his belongings. He found employment as an assistant lecturer in the physics department of the University of Birmingham, headed by Mark Oliphant, an Australian, another one of Rutherford's alumnai.
The British Chemical Society asked him to write a paper on the current state of nuclear physics. Frisch considered the possibility of a chain reaction in the paper and, influenced by the opinions of his old boss Niels Bohr, discounted it. Frisch then ran into another German physicist in England named Rudolf Peierls, a German of Jewish ancestry who had come to Cambridge in 1933 on a fellowship and had no choice but to stay there when Hitler purged the German educational establishment later in that year. Frisch ended up boarding with Peierls and his Russian wife, where the two physicists had plenty of opportunity to talk shop. Peierls thought that a nuclear weapon was possible, but he calculated that the "critical mass" -- the amount of fissionable material needed to set up an explosive chain reaction -- was "on the order of tons", meaning it wasn't a very practical idea. Although secrecy in nuclear research was starting to bite, Peierls published his result, on the basis that it was so discouraging that it could do no harm.
The war was quiet for the moment, the British and French simply staring off the Germans along the border in what was called a "sitting war". The Soviets disturbed the silence at the end of November 1939 by invading Finland -- which would prove all but a complete disaster for the Red Army, with an unusually harsh winter helping the Finns to blunt the Red offensive and kill vast numbers of Soviet troops. The Soviets would regroup and finally push the Finns into a corner four months later, but the territorial concessions obtained from the war were, as one Soviet general put it, "about enough to bury our dead". Worse, the weakness and disorganization of the Red Army, badly bled by purges, was apparent for the world to see.
As the "Winter War" neared its pathetic end in February 1940, Frisch and Peierls were reconsidering the mechanics of the chain reaction, using uranium-235. The result of the improved calculations were surprising: a nuclear explosion could be supported by a few kilograms of fissionable material. When Peierls calculated what the explosive yield of the weapon would be, the two physicists were "staggered". Frisch then worked out what sort of resources would be required to separate that quantity of uranium-235 from uranium-238; it would take a major investment of industrial resources, but concluded that "the cost of such a plant would be insignificant compared to the cost of the war." The concept had just ceased to be harmless.
They took their figures to Mark Oliphant, who immediately told them to write up a short paper on it. The paper calculated that 5 kilograms (11 pounds) of uranium-235 would have the explosive yield of thousands of tonnes of dynamite. It also provided preliminary details on how the bomb would be built, with two masses of uranium-235, which would be slammed together to create a critical mass. They speculated that the two masses could be slammed together by heavy springs, but emphasized that it would have to be done quickly, or the chain reaction would start before the masses were fully together -- resulting in "predetonation" and an explosive fizzle. A proper detonation would not only result in a horrendous explosion, it would also produce lethal ionizing radiation at the time of the blast and scatter around radioactive by-products.
The report concluded with a strategic survey, pointing out that such a weapon would be highly indiscriminate, causing massive civilian casualties. The report suggested that would render the use of the weapon unthinkable -- though within a few years the British, the threshold of the unthinkable having been broken by the Luftwaffe bombings of British cities, would be indiscriminately bombing German cities with little squeamishness over the deaths of enemy noncombatants. However, it also suggested the Germans were likely working on such a weapon and Britain had no alternative to developing it.
Oliphant added a cover letter and sent the report off to Henry Tizard, an Oxford chemist and chairman of the "Tizard Committee", a government board involved in consideration of advanced technologies for defense. The committee had already been instrumental in the development of British radar.
* That was in March 1940. A few weeks later, the war went hot again. In early April, the British announced that Norwegian waters would be mined to deny Norwegian resources to Germany. Norway had been neutral, but with its neutrality broken the Germans promptly invaded Denmark and Norway on 8 April. The Danes knew that resistance was futile and surrendered the next morning; the Norwegians fought on with assistance from British and French forces for another month, the leadership finally withdrawing to Britain to form a government-in-exile. The only compensation to the British was that the Royal Navy had ferociously chewed up the Kriegsmarine, the German Navy, during the operation. Niels Bohr remained in Denmark, believing he should stay on and use his authority to resist attempts by the Germans to impose Nazi laws on his country.
In the meantime, Tizard had been considering the paper Oliphant had sent. Tizard was skeptical but formed up an investigative committee chaired by G.P. Thomson, an Imperial College physicist and J.J. Thomson's son, the committee also including James Chadwick and John Cockcroft, another one of Rutherford's boys. The committee met for the first time on 10 April, as a report from the committee reported later: "We entered the project with more skepticism than belief, though we felt it was a matter that had to be investigated."
The necessity was reinforced by intelligence passed on by the French of German attempts to purchase heavy water from a Norsk Hydro, a Norwegian electrochemical firm, the only company in the world that produced the liquid. The company sold the heavy water for lab research at a hefty markup, with monthly production running to about enough to fill up a jug, which was all the lab market would bear. The German industrial giant I.G. Farben not only wanted to buy Norsk Hydro's entire stock, about enough to fill up an oil drum, and guarantee large follow-on shipments on an ongoing basis.
When puzzled Norsk Hydro officials asked why I.G. Farben wanted to buy such astounding quantities of heavy water at such expense, the Germans refused to say. The Norwegians refused to sell. A French bank had a controlling interest in Norsk Hydro and the news got back to France. French physicists were well aware that the most obvious reason to buy such massive quantities of heavy water was for moderating nuclear reactions, and in early March a French agent went to Norway to buy up the heavy water. The agent told the general manager of Norsk Hydro what was going on and offered to pay handsomely for part of the stock; the manager simply gave him the entire lot, which was smuggled back to France. Now the Norsk Hydro facility was in German hands.
The fear of what the Germans might be doing didn't affect the committee's skepticism at the outset. However, the group looked over the Frisch-Peierls report and quickly realized it was the genuine article, to be just as staggered by the possibilities. A second meeting on 24 April was characterized by obvious excitement. Further studies were initiated, with Frisch and Peierls out of the loop for the moment.
Then the war went much more active than the British and French had expected. On 10 May 1940, a huge German offensive jumped off, sweeping down through the Low Countries into northern France. Neville Chamberlain had just resigned, being immediately replaced by Winston Churchill. Although the situation didn't seem desperate at the outset, it quickly became so: the Low Countries fell, with the Germans then shattering the Anglo-French defense of Northern France. As the end of May neared, the catastrophe was evident.
The British Expeditionary Force fell back on the port town of Dunkirk; a massive sealift operation to 4 June managed to rescue most of the troops, but they had lost their equipment. The French sued for peace on 22 June 1940. The peace treaty that followed allowed the Germans to occupy northern France, while southern France remained under the highly conditional control of a French government in Vichy. Hitler felt, with some good reason, that he had just won the war: the defeat of France shocked the world, and he had no doubt that the British would soon give up the fight and make a deal with him. However, Churchill had absolutely no illusions about Hitler, wanted nothing to do with another "deal" like the one Chamberlain had made at Munich, and in public speeches all but spat in Hitler's face.
* Although the British were in a very difficult situation after the fall of France, Churchill became an embodiment of defiance against Hitler, with the British people rallying to his banner. Even many of the expatriates in Britain felt caught up in the patriotic fervor and desire to fight the Nazis.
The "nuclear club" was starting to investigate the brass tacks of building an atomic bomb. One of the first practical issues was isotope separation, sorting out uranium-235 from uranium-238. There were a number of different ways to do it in principle, but Peierls and Franz Simon -- yet another German Jew chased out by Hitler, with Simon ironically a holder of the Iron Cross First Class, just like Hitler -- felt that "gaseous diffusion" was the best way to go. The idea was to create a gas incorporating uranium and allow it diffuse through a membrane; the gas incorporating the lighter uranium-235 has lighter molecules and diffuses through the membrane more quickly. The "enrichment" of uranium-235 compared to uranium-238 was slight for any single session -- well less than a percent even under the best conditions -- so it had to be done over and over again to build up useful concentrations of uranium-235.
The tools for gaseous diffusion then available only worked on a small scale, far too small to obtain enough uranium-235 for building a bomb. As Frisch put it: "It was like getting a doctor who had after great labour made a minuscule quantity of a new drug and then saying to him: 'Now we want enough to pave the streets.'" Simon felt that it could be done by converting uranium to uranium hexafluoride gas (UF6) and passing it through a metal foil barrier full of small perforations, inserted in the middle of a cylinder. Experiments were performed to see if the idea could be made to work, though at the outset the gas being separated was water vapor and carbon dioxide -- uranium hexafluoride was a hideously nasty gas, thoroughly corrosive and toxic, known only too appropriately as "hex". Trying to figure out a material that stand up to hex promised to be a real problem.
* By late June 1940, G.P. Thomson's committee had taken a name: MAUD. It sounded like an acronym but wasn't, amounting to little more than a meaningless label chosen to confuse snoops into trying to pick apart what it stood for. The name wasn't entirely arbitrary: Lise Meitner had sent a telegram to a friend in England, with Meitner reporting that she had recently met with Niels Bohr and his wife Margarethe, concluding that they were well and adding: PLEASE INFORM COCKROFT AND MAUD RAY KENT. Cockroft was informed, obtaining a copy of the message. He thought that MAUD RAY KENT was an anagram; it was unscrambled to mean RADIUM TAKEN and seen as a hint of German nuclear activities. Actually, a few years later it was learned that Maud Ray was the name of a woman from Kent who had cared for Bohr's kids when the Bohrs were in England. The name MAUD had demonstrated its ability to mislead even before the committee adopted it.
The effort was starting to get attention in high places as well. In June, Peierls and Simon spoke with Frederic Lindemann about the prospects for an atomic bomb. Although Peierls commented that he didn't know Lindemann well enough "to translate his grunts correctly" -- Lindemann was not known for his social graces -- the two physicists felt they had made a good impression. They had, and Lindemann, who retained his close contact with Winston Churchill, was able to take the message to 10 Downing Street. Churchill regarded the "Prof", as he called Lindemann, as a prime source of scientific and technical advice, and the Prof's comments carried far more weight than any report dropped on Churchill's desk.
For the moment, however, Churchill had more immediate concerns. By mid-August, Britain was under air attack from the Luftwaffe, the German air force. Raids had begun in a spotty fashion during the Battle of France, but for a time Hitler had held off, hoping the British would come to their senses and make a deal with him. Churchill made it scathingly clear that wasn't going to happen, and so the "Battle of Britain" began. It seemed at the time to be a "softening up" phase preparatory to an amphibious invasion, and in fact the Wehrmacht was working on an invasion plan, codenamed OPERATION SEA LION.
In reality, Hitler didn't have the resources -- landing craft and the like -- for an amphibious operation of that magnitude, and Royal Navy superiority on the seas made the idea thoroughly dodgy, all the more so because of the way the Royal Navy had thrashed the Kriegsmarine off of the coasts of Norway. His thought processes on the matter seem in hindsight to have been confused and indecisive, as if he hadn't really thought the matter out before and was making things up as he went along, hoping they could be made to work. They couldn't, and in the end the German air assault on Britain ended up being an exercise in intimidation. Maybe if the British were hammered enough, they would dump the pigheaded Churchill and make a deal.
In any case, Hitler had other plans for conquest to work on. Nazi "victory fever" was a blessing for the British, since German work on advanced technologies, never very well coordinated by the backbiting, corrupt, inefficient, and ignorant Nazi leadership hierarchy, was not seen as particularly important. Resources were withdrawn, technical experts were drafted from research positions into the Wehrmacht. It would take a few years to realize this was a serious misjudgement.
The early phases of the Battle of Britain involved attacks on airfields and other military targets, a tactic that pressed the British Royal Air Force (RAF) to the wall. Then an accident intervened. On 24 August, German bombers missed an oil storage depot on the banks of the Thames and hit central London instead. Churchill immediately sent RAF bombers to hit Berlin at night. The raids were a joke as far as their ability to inflict damage went, but they were extremely successful in provoking Hitler into a rage. The Luftwaffe was ordered to attack cities -- sparing the RAF airfields at the expense of the suffering of British civilians. Whether that had really been Churchill's intent is unclear, but it gave the RAF breathing space, at a high cost.
The Battle of Britain went on into September 1940, but the Luftwaffe was taking a beating, suffering losses well greater than those of the RAF. By the end of the month, the Luftwaffe raids had switched from day to night, beginning what would become known as the "Blitz". At the time, the British had little ability to effectively fight back against night attacks, but neither did the Luftwaffe have the ability to perform precise attacks on targets in the darkness. The result was that the raids could inflict pain and create chaos, but they couldn't do much to seriously affect the British capability to resist. In fact, the attacks simply inspired a certain bulldog tenacity in the British, and reports from London back to America during the Blitz did much to persuade the American public that the time was coming to take on Hitler. The attacks also eroded British restraint towards retaliation in kind, and in time RAF Bomber Command would inflict a hideous retribution on the Germans.
* While the Blitz went on, at Oxford Franz Simon continued his work on uranium isotope separation for the MAUD committee. In December he completed his report, saying that a separation plant would cost about five million pounds and detailing its construction. He made up forty copies and drove them from door to door, not trusting the posts for such an important document.
* Anyone worried about the possibility that the Nazis might get the atomic bomb first had obvious reasons for concern in late 1940. The fall of Norway had put the world's only heavy-water factory into Hitler's hands; the fall of Belgium gave the Germans access to uranium, and the fall of France gave them access to a cyclotron then being completed under the direction of Frederic Joliot-Curie.
Experiments were being conducted by German scientists, though the results were not entirely encouraging: bungled measurements suggested, wrongly, that graphite was too effective at absorbing neutrons to be used as a moderator, leaving heavy water as the prime candidate. Work was also performed on selection of an industrial-scale process to separate U<235/92> and U<238/92>; the German researchers were startled by the estimates of the expense, and for the moment the focus was to be on use of heavy water as a moderator.
In the meantime, the Japanese were thinking about the atomic bomb as well. In April 1940, Lieutenant General Takeo Yusuda of the Imperial Japanese Army's (IJA) Aviation Technology Research Institute, who had been following scientific reports on fission, assigned a technically-trained aide, Lieutenant Colonel Tatsuaburou Suzuki, to investigate the concept. Suzuki came back with a report in October that generally focused on the availability of uranium, there being no reason to consider details if the raw materials were not available for further investigation. The report concluded that Japan had adequate access to supplies of uranium in Korea and elsewhere.
Consideration of details was passed by General Yasuda on to physicist Yoshio Nishina of the Riken laboratory of Tokyo. Nishina, who had been one of Niels Bohr's disciples in Copenhagen, set his people to work on investigations. In the spring of 1941 the IJA would authorize an atomic bomb development program.
* Back in the USA, work on the atomic bomb was slowly accelerating. In April 1940, while Tizard's committee was poring over the Frisch-Peierls report, Leo Szilard was chafing at the lack of motion from the US government: he had to prod his government contacts to even provide the inadequate sum that Teller had requested, and having done that the government demonstrated no more particular interest in the matter. To add to Szilard's frustration, Fermi still didn't seem particularly convinced himself that the chain reaction was practical.
After a spat between the two, Szilard went off to Princeton to talk to Einstein again. They composed another letter, this one emphasizing German nuclear research -- scientists who had recently left Germany for the United States brought with them alarming tales of German interest in the matter -- and sent it to Sachs. Sachs then went through a bureaucratic shuffle with the president, Pa Watson, and the Briggs Committee. The government's attitude was that the ball was in the physicists' court: at the initial meeting, they had asked for the money to buy graphite to see how useful it would be as a moderator, and now the committee was waiting on the results of the experiments before proceeding further. A second meeting on 27 April yielded precisely the same answer.
There was nothing to do but go on with the experiments, with Fermi determining that graphite would prove a useful moderator. Other experiments being conducted in parallel by his colleagues at Columbia demonstrated the superior possibilities of a chain reaction with uranium-235 over "natural" uranium, which was mostly composed of uranium-238. Szilard had finally managed to prevail on his colleagues to maintain secrecy; they weren't published and the Axis didn't get their hands on them.
In addition, the attitude of the US government was beginning to take a turn for the better. The change in weather was due to Vannevar Bush, who had not long before been a vice-president of the Massachusetts Institute of Technology (MIT) but who had in 1939 become head of the Carnegie Institution in Washington DC, a foundation set up by industrialist Andrew Carnegie in 1902 to promote scientific research. Bush had worked on US government defense technology development programs in the First World War and found it generally a case of the right hand, the military, unable to coordinate with the left hand, the scientists. With America obviously heading for involvement in a second world war, Bush decided that this time around things would be different, and he took the job at the Carnegie Institution to be close to the centers of power.
Bush wanted to set up a national research organization that would coordinate defense technology development, reporting directly to the White House so the military wouldn't just ignore it, and with its own source of funds so it would have a degree of independence of action. During the spring of 1940, after talking the matter over with prominent scientists, Bush came up with a proposal and arranged a meeting with Harry Hopkins, Roosevelt's chief aide and right-hand man. Bush and Hopkins hadn't met before but they hit it off well, with Bush finding that Hopkins was thinking of an "inventor's council" along the same lines. Encouraged, Bush spoke to contacts in the armed services, Congress, and the US National Academy of Sciences. On 12 June 1940, Hopkins introduced Bush to the president, with Bush pitching the idea. The meeting only took ten minutes -- Hopkins had discussed everything with Roosevelt ahead of time -- and ended with the president's approval. The "National Defense Research Council (NDRC)" was born.
The Uranium Council was absorbed into the NDRC, which meant the scientists and engineers, not the military, were in the driver's seat for funding nuclear research. For the moment, however, the NDRC was busy with a bewildering list of things to investigate, and NDRC officials still thought the atomic bomb sounded too much like science fiction. Since the Germans were clearly working on the concept, it had to be investigated, but the expectation was that the investigation would show the atomic bomb to be the fantasy it sounded like it was.
* However, new discoveries continued to erode that impression. On the West Coast, at the University of California at Berkeley, an experimental physicist named Edwin M. McMillan had begun bombarding uranium oxide samples with neutrons in early 1939, and came up with traces of unfamiliar radioactive materials. He suspected that he had found the next element beyond uranium, element 93, though proving the matter was tricky. McMillan enlisted the help of Emilio Segre, who had discovered technetium a few years earlier and was then at Berkeley, but Segre's chemical analysis came up negative.
McMillan wouldn't let go, however. In the spring of 1940, a Dr. Philip Abelson came to Berkeley on vacation. Abelson, who had a bachelor's degree in chemistry from Washington State University and a doctorate in physics from Berkeley, had been performing scientific research at the Department of Terrestrial Magnetism, a laboratory of the Carnegie Institute run by a prominent physicist named Merle Tuve. Back in California, Abelson was also skeptical of Segre's results, and so McMillan and Abelson took another shot at it. This time the elusive element 93 was positively identified. The first "transuranic" element had been discovered; McMillan dubbed it "neptunium", on the basis that the planet Neptune was the next beyond the planet Uranus.
A paper reporting the discovery was mailed off to the journal PHYSICAL REVIEW in late May 1940. Abelson then went back East, with McMillan pushing on to hunt for element 94. There were speculations floating around among the nuclear physics community at the time that transuranic elements might have significant implications for atomic power, and when James Chadwick saw the paper, he was shocked. A formal protest was channeled through the British embassy to the authorities in Washington DC and Ernest Lawrence, boss of the Berkeley lab, was reprimanded for giving away potentially dangerous secrets to the Axis. Even though America wasn't at war yet, people were finally taking security seriously.
* The increasing security went hand in glove with increasing Anglo-US cooperation. In the late summer, Churchill dispatched a team under Henry Tizard to the USA carrying Britain's most secret advanced technologies, particularly for radar, with a new high-frequency tube, the "cavity magnetron", taking center stage. (It is now found in every microwave oven.) Meetings took place, under the sponsorship of Alfred Loomis, a millionaire businessman and amateur scientist who was very well connected. Ernest Lawrence was a significant participant. The end result of the "Tizard Mission", with a little networking by Vannevar Bush, was the formation of a well-funded radar laboratory at MIT, know by the bland cover name of the "Radiation Laboratory" or just "Rad Lab".
The Rad Lab soaked up a significant component of America's best young technical minds, with Lawrence helping bring physicists into the fold; McMillan was working at the Rad Lab by the fall of 1940. Back at Berkeley, the hunt for element 94 continued, under the direction of a young chemist named Glenn T. Seaborg and with assistance from Emilio Segre. Using the cyclotron in the Berkeley lab, they accelerated charged particles and slammed them into a block of paraffin to smash loose neutrons and shower them into samples of a uranium compound, and by March 1941 had identified tiny samples of element 94. Since Pluto was the next planet beyond Neptune -- Pluto was still regarded as a planet in those days since it was estimated to be much larger than it really was -- Seaborg eventually decided to name it "plutonium". This time around the discovery was, with complete wisdom in hindsight, kept out of the science press. Further studies indicated that plutonium was an excellent material for building an atomic bomb.
* As far as Fermi and Szilard's work on an atomic pile went, on 1 November 1940 the NDRC finally came up with the funds -- $40,000 USD, not the paltry $6,000 USD Teller had asked for. With resources available, Fermi and Szilard were finally able to start building an atomic pile to prove that a chain reaction was really possible. Theory was all very well and good, but all the calculations did was demonstrate possibilities that had to be proven in the real world.
Although Szilard and Fermi were on good terms, they didn't work hand-in-glove, and so Szilard focused on procurement of pure graphite and uranium oxide while Fermi worked on the experimental setup. Szilard made inquiries to Monsanto, US Graphite, and other potential suppliers to find graphite of the appropriate purity, while he also obtained 225 kilograms (500 pounds) of uranium oxide from the Eldorado Radium Corporation. It wasn't easy to obtain such materials and it would take some months to track them down.
* In the winter of 1940:1941 James Bryant Conant, a prominent organic chemist and then president of Harvard University, went to Britain to follow up the technical contacts of the Tizard Mission by establishing an NDRC liaison office in the UK. He met with King George VI, Winston Churchill, and figures of lesser rank. Conant's mission was diplomatic, not technical, and he was reluctant to get too involved in details. Worried about security, he was downright skittish when atomic bomb work was mentioned to him, even after Prof Lindemann described a "bomb of enormous power" over lunch. Conant didn't follow up the matter, considering the notion too outlandish and figuring that it was no business of his.
Nobody else in positions of power in the USA seemed to think it was particularly their business either, and Ernest Lawrence was becoming increasingly frustrated with the status quo. He resolved to change matters, meeting on 17 March 1941 at MIT with MIT with Alfred Loomis and Karl Compton, president of MIT and a physicist by training, warning them that America could not let the Nazis be the first to build the atomic bomb. They were impressed by Lawrence's pitch, but when matter worked its way up to Vannevar Bush, he came to the conclusion that Lawrence was a loose cannon. Bush talked to Lawrence in New York City on 19 March and told him to toe the line: the NDRC was his show and if Lawrence wanted to lobby he would have to do it the normal channels. If he didn't, the NDRC would shut him out.
However, Bush had been essentially concerned with protecting his authority in the confrontation with Lawrence, and was actually more confused about what to do about atomic bomb research than he let on. Reports were filtering back from the UK on MAUD work, saying the matter was too important to be ignored. Bush finally became uncomfortable enough to work with Briggs and Arthur B. Jewitt, head of the US National Academy of Sciences (NAS), to set up a review committee that had the technical expertise to pass judgement on the prospects of an atomic bomb. The NAS committee ended up with three members: Ernest Lawrence; a prominent retired physical chemist named William D. Coolidge who had run General Electric's research labs; and physicist Arthur Holly Compton of the University of Chicago.
Arthur Compton was the younger brother of Karl Compton and had won the Nobel prize for his discovery of the "Compton effect", the scattering of photons -- light particles -- by electrons. He was bright, pleasant, vigorous, with the looks of a 1930s movie leading man, and very devout -- his father was a Presbyterian minister and his mother a Mennonite dedicated to missionary work. Although Mennonites are pacifists, the war in Europe had already convinced Compton that the need to defeat the Nazis overrode an abstract consideration of principle. When asked to head the review, he was quick to accept.
The NAS committee deliberated for several weeks in the spring of 1941, and finally produced a seven-page summary report that was handed over to Jewitt on 17 May 1941. The report concluded that it would be possible to produce radioactive materials for poisoning enemy territory, use atomic power to propel ships and particularly submarines, and build "violently explosive bombs." The report concluded that an atomic bomb could be available as early as 1945 and said research should go forward.
Jewitt was generally impressed with the NAS report, but Bush paid it little mind -- partly because he was distracted at the time, being engaged in strenuous political lobbying and organizational politics. The NDRC was a fine thing but it had one major limitation: it was strictly a research organization, with no capability to develop weapons and tools. Bush was working up a new organization, the "Office of Scientific Research & Development (OSRD)", which would be headed up by Bush and would report directly to the President of the United States. It would be formally created in June. The NDRC would become an advisory organization to the OSRD, with Bush lining up James Conant to take charge of the earlier organization.
Conant looked over the NAS report and said to Bush that his conclusions from it were "almost entirely negative". It wasn't surprising that Bush seemed confused about the matter, unwilling to give up on it but uncertain about a course of action.
* The night Blitz against England had faded out in May, much to the relief of Britons, but the silence left open the question of what Hitler was planning. Thanks to radar developments, the RAF had been taking an increasing bite out of the night raiders, but not to the extent of inflicting unacceptable losses on the Luftwaffe and driving them off. It wasn't too difficult to suspect that German air power had been withdrawn from the skies of Britain to be put to use elsewhere. On the morning of the summer solstice, 22 June 1941, Hitler invaded the USSR, massively escalating of the war.
This event had the effect of making Conant even more uncertain about atomic bomb research: he believed that resources needed to be put into weapons that would be available very soon, not into blue-sky projects that might pay off years down the road. Conant discussed the matter with Bush, who realized that he needed to make a decision. The NAS review committee was reconstituted to review the original report, with the staff adjusted to provide a more practical and less theoretical viewpoint. Compton dropped out, Coolidge took charge, and two senior engineers -- one from Bell Laboratories and the other from Westinghouse -- signed on. They went over the first review in early July and endorsed it. Bush continued to equivocate.
However, American visitors to the UK also provided more detailed feedback on the MAUD work to Vannevar Bush, and when the committee issued its final report on 15 July 1941 -- to then disband -- Bush got a draft copy. The report was a detailed blueprint for the development of the atomic bomb; it concluded that it would be practical to build such a weapon, that it would be decisive in the war, that the work should be performed at the "highest priority", and that collaborative efforts with the USA be extended to that end. Bush now tilted towards the atomic bomb, but he remained cautious. During July he spoke with Vice-President Henry Wallace -- a plant geneticist by training -- about the prospects of funding an atomic bomb development program, but then Bush decided to stall again, waiting until he obtained the full MAUD report.
* Edward Teller, who had along with his wife become an American citizen in March 1941, had been teaching at George Washington University but chafing to get more involved in fission research. Through the help of some friends he managed to obtain a position at Columbia, where he could work with Fermi and Szilard. Teller was skilled at helping smooth out the disputes between the two physicists and his presence was appreciated.
Sometime in September, Teller remembered later, he had lunch with Fermi, who passed on a suggestion to Teller on the way back to work. Suppose, Fermi said, one was to use an atomic bomb to heat up a mass of deuterium, heavy hydrogen. The temperature would be so high it might cause the deuterium to fuse into helium, producing a bang several orders of magnitude bigger than that produced by a fission bomb. Teller found the idea of a "fusion bomb" fascinating and dove in, performing calculations to see if Fermi's idea was possible. A week later he told Fermi it wasn't, and Fermi saw no reason to question the conclusion. In fact, Teller would turn out to be wrong.
Fermi actually wasn't the first to suggest the idea: a Japanese physicist named Hakutaro Hagiwara of the University of Kyoto had come up with same notion back in May. No matter who thought of it first, at the time it was an almost irrelevant speculation, since a fusion bomb would need a fission bomb to set it off. Nobody was close to building a fission bomb just yet.