Chapter Two - The Two Billion Dollar Bet

"A study of the shipment of (bomb-grade uranium) for the past three months shows the following...: At the present rate we will have 10 kilos about February 7 and 15 kilos about May 1."xxvi
  From a memo written by chief Los Alamos metallurgist
  Eric Jette, December 28, 1944.
  The uranium bomb required 50 kilos by July 24.

  By mid-May of 1945, as U-234 was being escorted in to Portsmouth, almost two billion dollars had been spent on the Manhattan Project, making it the greatest wager ever to that point in time.  The man who threw the dice, and was about to lose it all, was Brigadier General Leslie Richard Groves.

   In the course of just three years, using taxpayers' money unbeknownst to them, Groves had built a secret industry that outstripped any other enterprise on earth.  He had purchased vast tracts of land in Washington state, Tennessee, New Mexico and elsewhere, engulfing hundreds of thousands, if not millions, of acres.  On these reservations he built huge factories that contained the most advanced technology on the face of the earth.  He made multi-million dollar deals with many of the globe's top companies - companies like DuPont, Westinghouse, and Raytheon.

  To support these contracts and newly constructed facilities, he built whole towns, complete with roads, schools, postal services, banks, unions and everything else necessary to maintain a community.  And he manned these municipalities with hundreds of thousands of workers and their families, including many of the greatest intellects alive.  No fewer than 13 of the physicists and chemists involved in the Manhattan Project either had already won, or later would go on to win, the Nobel Prize.

  All of this had been assembled and focused on one task - to make an atomic bomb. Now the effort seemed to be exploding in his face.

  The construction of an atomic bomb requires two things: enough fissile material to achieve critical mass and explode, and a trigger to start the explosion. Despite the immense investment, progress was remarkably slow on both requirements. Contrary to presently accepted history, by mid-May of 1945, neither requirement had been obtained. According to recently uncovered information from contemporaneous Manhattan Project documents - enriched uranium production charts and memos on metallurgical progress and other never-before-revealed sources, including first-hand information revealed to the author during interviews with Manhattan Project personnel - the objectives still had not been achieved. And Groves had a third requirement that was about to make the other two points moot.  Time was a factor, and it was running out.

  Germany, the chief rival in the atomic bomb race according to intelligence reports,xxvii - notwithstanding its now-surrendered status - planned to provide its Asian ally, Japan, with an atomic bombxxviii to use in the Pacific. U-234 had not been the only U-boat scheduled to voyage to Japan.xxix At least one other vessel, possibly more, apparently also carried in its belly enriched uranium intended for Tokyo.

  Apparently, the race for the atomic bomb was much closer than most would have supposed - possibly even closer than Groves thought. After all, the General had spy Paul Rosbaud, code named Griffin, keeping him informed of German progress and possibly even of shipments to the Island Nation.  There seems to have been no such counterpart in Japan to serve Groves as a conduit.  If uranium had been sent to Japan, as appears probable, Groves most likely knew through Rosbaud, but what was happening to it in The Land of the Rising Sun he could only guess.

  Groves was not pressured by this threat only, he also had to worry about the fact that, should the Allies' war effort survive the German/Japanese conspiracy, in July, Truman, Churchill and Stalin were scheduled to meet in Pottsdam to partition the remnants of Europe that the Third Reich had left behind.  The result would go a long way toward deciding the balance of power in the post-World War Two Additionally, Stalin had already declared his intent to go to war with Japan in mid-August.xxxi The United States and Britain could then expect to share the Asia/Pacific region, as well as Europe, with Russia; leaving the Communist Bear with a much greater share of the globe than it had earned or that either democracy cared to relinquish.  A demonstration of the power of 'the bomb' to end the war with Japan - displaying to the rest of the world that the United States possessed this awful weapon - would establish America as the military leader of all nations; and would certainly impact these negotiations and the resulting socio-political complexion of the modern age.

  But here stood Groves, as yet unsuccessful, with the sands of time slipping through his hands.  Despite massive, sometimes reckless, always all-out spending; despite playing all the odds, even those with the slimmest chance of winning; despite assembling the greatest braintrust ever brought together in the United States; and even despite Groves' own expansive experience and unquestioned self-confidence, the gamble appeared to be a bust.

  Almost $2 billion to produce just over 100 pounds of fissile material for the uranium bomb and about 30 pounds for the plutonium bomb, and a way to detonate them, had not been enough to meet the deadline.  The cost, had the effort been successful, equaled almost $100,000 per ounce of enriched uranium - in 1945 dollars. While the great effort had been successful enriching uranium and reducing it to its explosive metallic form, it appears that over one-half of the hard-earned material never would see a uranium bomb; it was secretly being used to fuel the huge plutonium-breeding reactors at Hanford, Washington. 

The reactors, fueled by the enriched uranium, would produce several orders of magnitude more explosive plutonium than the enriched uranium they consumed; promising quicker, easier, less expensive bombs, and many more plutonium bombs than the single uranium bomb that could have been produced with the amount of enriched uranium consumed in the reactors. 

The end result for the uranium enrichment effort was that less than half of the enriched uranium metal required for a nuclear device was available by mid-May, according to calculations based on data given in a memo written by top Manhattan Project metallurgist, Eric Jettexxxii and with which later information agrees, as do Jette's resulting predictions.  Even doubling that rate of output, the program would fall far short of the amount required for a bomb to have been dropped in early August.  And yet the bomb dropped on Hiroshima is known to have been a uranium bomb.

  Jette's calculations correspond almost precisely with and are validated by information supplied in Richard Rhodes' book The Making Of The Atomic Bomb, in which Rhodes sets the amount of enriched uranium metal available for a uranium bomb by April 1945 as "a near critical assembly."xxxiii  According to Rhodes' calculations, which are based on information recorded at the time by James Bryant Conant, one of the scientific advisors on the Manhattan Project and president of Harvard, 42 kilograms, or 92.4 pounds, of enriched uranium is equal to 2.8 critical masses.xxxiv 

One critical mass therefore, the amount barely available in mid-April with only three months of production time left, is exactly 15 kilograms, or 33 pounds, the amount Jette predicted would be available by 1 May. In theory, one critical mass was all that was needed to make a bomb; but in reality, due to inefficiencies caused by impurities still mixed throughout the enriched uranium, the bomb actually required over three critical masses in order to achieve the level of explosion desired.  Robert Serber, who wrote The Los Alamos Primer, gives the total figure for the uranium bomb at "about 50 kilograms,"xxxv over three times critical mass.

  The point is, in mid-April, after almost a year of processing enriched material, because of the demand to use enriched uranium to produce the much more practical and powerful plutonium bomb, the uranium program had barely one-third the processed uranium required to make a uranium bomb.

  The uranium bomb option would have been inconsequential with a valid plutonium bomb but it was later discovered that the plutonium bomb could not be detonated efficiently enough to create a successful explosion.  Now, with enriched uranium stocks depleted by plutonium demand and the plutonium bomb, in turn, undetonatable, the entire enormous enterprise appeared destined for defeat.

  Yet even now, both Groves and his superiors knew that the gamble had been a strategic imperative.  To sit on the sidelines of international influence, when America was just coming into its own; to allow fascist, communist or imperialistic governments to control the destinies of the countries of the world - especially those of free nations - was immoral and inconceivable.  The wager was essential no matter how small the chance of success.

  For the opportunity even to sit at the table and bet, knowing that the stake was world dominion, Roosevelt had anted-up $2 billion, and with foreknowledge some say, had allowed Pearl Harbor to be bombed. Thus the United States entered the war for a chance to play the nuclear game.  Now the deck almost had been played out and, as is so often the case in war and politics, it appeared there would be no clear winner, only varying degrees of losers.

  Even Groves, from the very beginning when he took over the Manhattan Project from Colonel J.C. Marshall in September of 1942, xxxvi despite all his later efforts, had given the improbable scheme a small chance of success.xxxvii  Marshall had been the Manhattan, New York district engineer for the Army Corps of Engineers.  He was assigned to the project shortly after Roosevelt received the famous letter in late 1939,xxxviii written by Albert Einstein at the behest of two renowned Hungarian physicists, Eugene Wigner and Leo Szilard, that explained the destructive realities of nuclear energy and that the Germans were working feverishly on its unleashing.  The letter was delivered personally to the president by economist and Roosevelt confidant Alexander Sachs, who read it to the president aloud in the oval office.

  Roosevelt, by his own native genius, seems quickly to have understood the full implications of the development.  Before Sachs left the White House that day, the President had established a committee for pursuing nuclear energy.
  But despite Roosevelt's quick reflexes, the work moved slowly. Responding to a report by aid Vannevar Bush two years later, in the early Spring of 1942, Roosevelt - who seemed to understand the urgency of the atomic initiative better than most of his nuclear advisors - wrote emphatically, "The whole thing should be pushed not only in regard to development, but also with due regard to time.  This is very much of the essence." xxxix  The President seems to have been the only one who understood the full gravity of the circumstances.

  When James B. Conant reported in mid-1942 that Germany might be ahead in the arms race by as much as a yearxl - and despite traditional history there is evidence this was so - impetus was finally given to the program, but it still took until September of that year to recruit Groves.

  The colonel who had a decade earlier overseen the construction of the great symbol of United States military might - The Pentagon - had been made a brigadier general responsible for the development of the weapon ultimately destined to guarantee that power.  Groves' response to learning that the project for which he was being recruited could single-handedly win the war speaks volumes about the size of his ego and the extent to which his experience building the Pentagon and handling a $10 billion budget as the number two man in the Corps of Engineers had alienated him from feelings of mere human dimensions.  He said simply: "Oh."xli

  The one thing Roosevelt didn't need to worry about with Groves was wasted  time.  The general went to work immediately, criss-crossing the country to familiarize himself with the theory and processes and all of the research and development programs presently in progress.  What he found was discouraging.

  First, uranium, at least at the time, was rare and relatively expensive.  Experts in the United States knew of only a few light deposits of the very heavy element but were doing little to mine it.  Up to that point, there had not been a lot of use for uranium except in ceramic glazes.  To get what it needed, the Manhattan Project would have to go outside of the sovereign borders of the United States, or so it seemed.

  In a quirk of circumstance, over 1,000 tons of raw uranium ore had been sent to New York and was sitting in open steel drums in a warehouse on Staten Island.xlii  The uranium had come from what Groves later identified, wrongly, as the richest uranium reserves in the world - those of the Belgian Congo - by way of Belgium and the Brussels-based company that owned the mines, Union Minière.  Union Minière had provided rare-earth minerals for radiation studies performed by the famous French Curie family.

  Groves' misstatement that the Belgian Congo held the richest uranium reserves is the lead-off in a long litany of hidden or half-truths, shaded assertions and outright lies later employed to paint a public picture decidedly different than those events that actually transpired.  The details of this deception will be outlined later. Simply put, the mischaracterization is a single brushstroke - among a multitude - that makes up part of a larger picture created after-the-fact to hide the evidence that the Third Reich already had in its possession far more raw uranium than it would ever need for its purposes; and that it also held within its hands total control of the largest and most high-grade uranium ore deposit in the world, that at Joachimsthal, Czechoslovakia.

  The president of Union Minière, M. Edgar Sengier, having been approached previously by agents of the German government to buy the valuable mineral stocks, carefully avoided closing a deal with the German emissaries.  Sengier knew of uranium's ultimate possibilities. Through his dealings with the Curies he had been invited by Frederic Joliot-Curie in 1939 to help build an atomic bomb in the Sahara desert, according to General Grove's book, Now It Can Be Told.xliii

  Such a fascinating revelation from Groves demands a question: Build an atomic bomb for whom?  Certainly Joliot-Curie was not planning it for personal world dominion.  He must have known such a project could only be accomplished at enormous cost and effort if it were possible at all.  Given later accusations regarding Joliot-Curie that show every indication of having been true, and despite his reported membership in the French resistance, it is possible that he planned on consorting with the Germans.  At any rate, Sengier appears to have declined that offer, as he presently did the agents' bid for the bulk uranium stores.

  Instead, right under the Germans' noses, he had shipped the uranium to the United States for safe keeping.  Once having made such a prudent and noble move at the potential cost of the loss of great profit for himself and his company, not to mention the threat to his physical safety that defying the Nazis could mean, he tried to make a deal with the United States to cover his lost investment. But the old Manhattan Project regime, for whatever reason, had not responded.

  Groves, on the other hand, now snapped it up.  Over twelve hundred tons of uranium might be enough to harvest the 110 pounds of U235 needed to make a bomb.  But raw uranium ore is only the basest form of uranium.  From the ore, full of a variety of polluting elements and minerals, pure uranium must be refined; a considerable process in and of itself.  Then the real challenge begins:  Uranium atoms, like most elements, exist in various versions called isotopes.  These different versions of the atom contain the same numbers of protons and electrons, which define the element and create its characteristics, but have a different number of neutrons, which, while not changing the element's characteristics, alter the atom's structure and weight.

  The vast majority of uranium is the isotope identified as U238 (U for uranium, 238 for this particular isotope's atomic weight), which constitutes 99.3 percent of all of the uranium on earth.  The remaining less-than-one percent is mostly U235 - the fissile form of uranium. Unlike the more balanced lattice-work of the U238 nucleus, the unbalanced structure of a U235 nucleus is unstable.  When the nucleus is struck with enough force by a passing neutron or other sub-atomic particle, the nucleus will fracture and divide, leaving two sub-uranic elements behind, while at the same time releasing additional neutrons along with a portion of the energy that had kept the uranium nucleus bound together.  This nuclear energy is by far the strongest force known to man and, although because of each atom's minuscule measurements the energy released seems like an infinitesimal force, actually, the power discharged is proportionally enormous.

  To appreciate the truly diminutive size of an atom, journalist Chapman Pincher has given the following scale against which the minuteness of atoms can be measured.  Envision a straight pin magnified so large that its head lay in London, England and its point terminates in the country of Bangladesh, on the far side of India - a distance covering approximately one-third the circumference of the earth.  The atoms of such a needle would be the size of golf balls.xliv  Yet according to real-world examples cited in Richard Rhodes' book, The Making of the Atomic Bomb, the strength of the nuclear force in a single atom contains enough energy to make a grain of sand jump, a mass hundreds of thousands if not millions of times greater than that of an atom. Rhodes adds that there is enough power in one cubic meter of uranium to lift one million million kilograms (or 2.2 million million pounds) 27 miles into the air.  Put another way, one pound of uranium can produce nine million kilowatt hours, for which New York City would pay about $1.2 million.

  Almost as soon as the first atom was split, physicists the world over realized that if these great forces could be systematically released and controlled in large quantities of atoms, an enormous source of energy would be made available.  On the heels of this realization came the revelation that if this energy could all be released in an instant, a super powerful explosion would occur, the likes of which had not been experienced on earth.

  Calculations and experiments soon proved that in properly prepared uranium, for each neutron that split a nucleus, of the many neutrons that would be released an average of two-and-a-half would hit and split other nuclei, which would split yet two more each, and so on - creating a chain reaction that theoretically could sustain itself until the nuclear fuel ran out. This knowledge, along with the fact that Nazi Germany was the first to uncover these cosmic secrets, is what caused Einstein, Szilard and Teller to write their famous letter of warning to Roosevelt.

  The great challenge of this task for all warring factions was in accumulating enough uranium that was predominantly pure U235, and whose atoms were closely enough positioned together, so that released neutrons could reach the surrounding U235 atoms and create a chain reaction. This meant that a method had to be found to virtually pluck U235 atoms one at a time from the average of 140 U238 atoms surrounding each one of them, and gather them together in a single body.  Given the acutely minute, super-submicroscopic media to be meddled with and the overwhelming ratio of U238 to U235, the prospects were surely daunting.

  When Groves had been given the assignment to oversee this Draconian task in the fall of 1942, however, he had nonetheless been told by his superior that the project was well in hand.  He was stunned to find upon his review that so little had in fact been accomplished.

  For starters, almost no one in the United States had been able to technically devise how to separate U235 from raw uranium.  Thus far everything was theory - with one small exception.  Nobel Laureate Dr.Ernest Lawrence at the University of California in Berkeley was just in the process of developing an electro-magnetic mass separator that, using mammoth-sized magnets and hundreds of thousands of volts to power them, could separate U235 from U238 to at least a nominal degree of enrichment.  Groves presumably was encouraged when he heard about the breakthrough.

  Traveling to Berkeley, the General entered Lawrence's laboratory and was brought to where he could see the enriched uranium product - he was led to a microscope. Undoubtedly dumbfounded and disappointed, Groves bent over the lens to see a spec of uranium that measured 75 micrograms of only 30 percent enriched uranium.xlv  

For comparison, a dime weighs 2,500,000 micrograms. He knew by this time that the amount needed for a bomb was still a matter of theory but that estimates ranged anywhere from five pounds to 600 pounds (Manhattan Project scientists would ultimately conclude the bomb would need to be about 110 pounds) of from 80 to 90 percent enriched material. Compared against the meager offering he was staring at through the microscope lens, the requirement to produce any and all amounts of material between those few micrograms and the roughly calculated critical quantities made the chances of achieving bulk production amounts in a usable time frame so astronomical as to be meaningless.

  Despite Groves' disappointment, the perennially optimistic Lawrence assured the General that what he had seen represented great strides, and that from this feeble foundation he could build a device capable of separating uranium in mass production quantities - tens of grams at a time. Groves was nonplused.  They were still talking in fractions of ounces.  But Lawrence's process was the best chance he had - for everyone else so far, any kind of serious isotope separation had been impossible.xlvi

  While in Berkeley, the new-formed cradle of American nuclear research, the General also took the time to visit several other researchers, experimenters and theoreticians, and this proved to be fortuitous.  He met J. Robert Oppenheimer, the man Groves would eventually choose to direct the laboratory that would develop the United States atomic bomb. Robert Serber, a close friend and co-worker of Oppenheimer's, in his preface to the post-war publication of The Los Alamos Primer, which he wrote at Oppenheimer's request to orient newly arriving Manhattan Project personnel into the program, described Groves' ego-emanating entrance the first time they met.xlvii  Apparently Groves had no more than entered the room, when he removed his jacket and handed it to a colonel he had "in tow," and curtly ordered the high-ranking officer to find a laundry and get his tunic cleaned.

  Oppenheimer, on the other hand, was quite a different personality.  He was young, ascetic, wealthy, and seemingly frail, although later events would prove him to be a glutton for physical, psychological, emotional and intellectual abuse.  Oppy, as he was affectionately known by friends, was scientifically and clinically critical while at the same time embracing Far Eastern metaphysical mysticism.  The paradox made him an astonishing choice for project director.  The greater half of the astonishment was that Oppy was a theoretician, not an experimentalist.  The new laboratory was, of necessity, going to be nothing if not overwhelmingly experimental.

  Oppenheimer's lack of experimental experience caused many who coveted the position, or who otherwise had what appeared to be legitimate concerns, to cry foul.  Groves would have none of it.  He had quietly grasped Oppenheimer's unique genius, his brilliantly quick analytical and intuitive facility and a talent for exciting people about the work, and was not about to let him go.

  What concerned Groves more was the future lab director's leftist connections.  Not that Groves felt they were much of a hindrance to Oppy's doing the job, but security checks had to be performed and they soon revealed that not only had Oppenheimer once been a registered member of the American Communist Party, but his wife, brother and ex-fiancé, as well, were presently members or had been members at one time.

  The endless pursuit by military security to rectify this apparent security breach kept Groves almost continually in a position of having to protect his chief deputy.  His willingness to do so is surely a strong endorsement of Groves' belief and confidence not only in Oppenheimer but in his own extraordinary ability as a judge of people. The results Oppenheimer brought forth stand as an undeniable testament to the General's sense of 'good horse flesh.'  What is most remarkable is that although he had considered others, Groves was 99 percent decided Oppy was his man after only one or two meetings.

  A month later, in November 1942, Groves and Oppenheimer, with a handful of others, were at a boys ranch standing atop a 7,200-foot-high plateau in New Mexico.  Oppenheimer, who owned property in New Mexico and loved the vast, scenic expanses of countryside, had suggested the location over several rivals, some close by, others as far away as Utah and Washington state.  As they stood under the cottonwood trees - for whose Spanish appellation the boys school had been named, Los Alamos - Groves consented to purchase the property as the sight for America's new atomic bomb laboratory.xlviii

  A full four months after that, in the end of March 1943,xlix the small group would finally return, accompanied by a nucleus of scientists that would ultimately grow to be one of the greatest collections of intellects concentrated on one task ever: Enrico Fermi, Emilio Segré, Hans Bethe, Otto Frisch and many others, all Los Alamos personnel during the war, were just a few of several scientists at the project who had already won or would go on to win the Nobel Prize and other top awards of science.  Along with them they brought equipment commandeered from laboratories across the United Statesl and a support force of almost 5000 people, many with their families.

  Despite the thin chance, and so far almost non-existent success, that the American effort had to achieve separating uranium isotopes, General Groves made an early and full commitment to the project.  Before he had pinned the new general's star on his collar (an inducement to get him to accept the Manhattan Project assignment over his preference to serve in a theater of war), before he even ran to Berkeley to find what level of scientific talent was available, Groves signed the directive that began the purchase of 59,000 acres of mostly undeveloped land in Eastern Tennessee.  The complex built there would soon come to be known as Oak Ridge, and it would house most of the technologies tried - many of which would fail or only achieve nominal success during the war - to enrich production quantities of bomb-grade

  On the site eventually would be established a gaseous diffusion isotope separation plant what would utilize hundreds of thousands of stacks of pipes in an all-but-failed effort to enrich uranium before the war was over.  This plant would enclose almost 42 acres under a single roof and cost one-half a billion dollars, the greatest single expenditure of the war-time program.  A liquid thermal diffusion plant under the operation of the Navy would be constructed as well.  By far the most successful form of isotope separation would be the electromagnetic isotope separators pioneered by Ernest Lawrence.

  Groves would one day brag that every gram of U235 produced for the Manhattan Project had been processed through Oak Ridge's magnetic isotope separators - called calutrons, after the California State University (Cal. U.) at Berkeley, where it was developed.  But even with the calutrons, none of these processes were close to being viable at production-level quantities at the end of 1942.  And the famous claim that all of the uranium enriched passed through the celebrated calutrons during that process has now become questionable, based on recently discovered information.

  Five days less than a year after the bombing of Pearl Harbor, on December 2, 1942, Italian émigré physicist Enrico Fermi and his research team, working in an old squash court under the University of Chicago's Stagg Field grandstand, opened another door leading to an atomic bomb - they produced the first man-made self-sustaining nuclear chain reaction.lii  The experimental reactor pile, built of over 400 tons of graphite and uranium, provided not only proof that a slow chain reaction could be achieved and controlled, but the means to further test the theory that uranium bombarded by neutrons will absorb those neutrons until it metamorphs into a new and previously unknown element - which the theorists called plutonium.

  Plutonium, besides being the first man-made element, would fission as easily as U235.  The bomb makers counted this a blessing. And plutonium as an element all its own, rather than an isotope of one, had chemical characteristics that were different from other substances.liii  By finding these differentiating properties, the plutonium could then be separated from its parent, uranium, by chemical means, a far less expensive and comparatively easy process than the impossibly demanding physical separation procedures required to harvest one atom at a time, as was necessary to enrich uranium.  There was now a second, much better, option for developing an atomic bomb.

  Hopes were high.  Everyone from Groves and Oppenheimer to Fermi and Lawrence were enthused over the plutonium prospect.liv  In fact, the whole object of creating a reactor pile changed from creating heat to make steam for industrial power to breeding plutonium for a bomb. Groves immediately went to work establishing a plutonium pilot plant at Oak Ridge, as well as beginning the procurement of property in the state of Washington for the purpose of constructing a series of plutonium breeding reactors.

  The researchers, however, soon found problems with the plutonium option.  Previous plutonium breeding experiments had been performed in a cyclotron that could bombard target uranium with only very small amounts of neutrons.  The result was the expected transmutation of U238 to plutonium 239 (Pu239).  The comparative flood of neutrons released in a chain reacting pile, however, placed the parent U238 awash in stray neutrons.  While some of the U238 absorbed one neutron to become Pu239, many of the nuclei absorbed two neutrons, transmuting to Pu240, a highly spontaneous fissioning isotope of 

This would have been good news except that the spontaneous fission rate of Pu240 is three times faster than that of U235 or Pu239.  The latter two isotopes fission slowly enough that, theoretically, to assemble a critical mass one needed simply to shoot one subcritical piece of material into another piece. The total of the two pieces came together to achieve critical mass at about 3,000 feet per second - roughly the velocity of a high-powered cannon.  Voile, a nuclear explosion.

  Pu240, on the other hand, releases its nuclear energy, in the form of extremely high temperatures, so fast upon fissioning that the resulting burst of heat blows the surrounding atoms away. The probability that released neutrons will collide with, and therefore split, other neutrons is greatly reduced - thus the chain reaction ends before it has ever begun.

  Groves and his cadre of scientists now had a challenge creating a plutonium bomb as perplexing and problematic as the original isotope separation assignment.  They must find a way to trigger a critical assembly, in other words, to move multiple blocks of matter at velocities no human, for any reason, had ever envisioned attempting, and to move them in less than 1/3000th of a second.  The plutonium option was now just as much a long shot as the original uranium bomb.



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