Manhattan Project
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2008-07-16T20:18:03Z
Ahoerstemeier
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{{otheruses4|the World War II nuclear project|other uses of the name "The Manhattan Project"}}
[[Image:Trinity shot color.jpg|right|thumb|The Manhattan Project resulted in the creation of the first [[nuclear weapon]]s, and the first-ever [[nuclear test|nuclear detonation]], known as the [[Trinity test]] of [[July 16]], [[1945]].]]
The '''Manhattan Project''' was the project to develop the first [[nuclear weapon]] (atomic bomb) during [[World War II]] by the [[United States]], the [[United Kingdom]], and [[Canada]]. Formally designated as the '''Manhattan Engineer District''' (MED), it refers specifically to the period of the project from 1941–1946 under the control of the [[United States Army Corps of Engineers|U.S. Army Corps of Engineers]], under the administration of [[General]] [[Leslie Groves|Leslie R. Groves]]. The scientific research was directed by American [[physics|physicist]] [[Robert Oppenheimer|J. Robert Oppenheimer]]. <ref>{{cite book
| last = Hakim
| first = Joy
| authorlink =
| coauthors =
| title = A History of Us: War, Peace and all that Jazz
| publisher = Oxford University Press
| date = 1995
| location = New York
| pages =
| url =
| doi =
| id =
| isbn = 0-19-509514-6 }}</ref>
The project's roots lay in scientists' fears since the 1930s that [[Nazi Germany]] was also [[German nuclear energy project|investigating nuclear weapons of its own]]. Born out of a small research program in 1939, the Manhattan Project eventually employed more than 130,000 people and cost nearly $2 [[1,000,000,000 (number)|billion]] [[USD]] ($24 billion in 2008 dollars based on [[consumer price index|CPI]]). It resulted in the creation of multiple production and research sites that operated in secret.<ref>Stephen I. Schwartz ''Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons.'' Washington, D.C.: Brookings Institution Press, 1998. [http://www.brookings.edu/FP/PROJECTS/NUCWCOST/MANHATTN.HTM Manhattan Project expenditures]</ref>
The three primary research and production sites of the project were the plutonium-production facility at what is now the [[Hanford Site]], the [[uranium]]-enrichment facilities at [[Oak Ridge, Tennessee]], and the weapons research and design laboratory, now known as [[Los Alamos National Laboratory]]. Project research took place at over thirty sites across the [[United States]], [[Canada]], and the [[United Kingdom]]. The MED maintained control over U.S. weapons production until the formation of the [[United States Atomic Energy Commission|Atomic Energy Commission]] in January 1947.
==Origin of name==
[[Image:Tower270.jpg|thumb|upright|270 Broadway from the east in 2007]]
The project was originally coordinated from the U.S. Army Corps of Engineers [[North Atlantic Division]] headquarters on the 18th floor of [[Tower 270|270 Broadway]] near [[New York City Hall]] in [[Manhattan]].<ref name=Broad>[http://www.nytimes.com/2007/10/30/science/30manh.html "Why They Called It the Manhattan Project" by William J. Broad - ''New York Times'' - October 30, 2007]</ref>
The initial proposed name was "''Laboratory for the Development of Substitute Materials''."<ref name=Broad/> Fearing the name would draw undue attention ("I felt that it would arouse curiosity of all who heard it"), General [[Leslie Groves]] requested a name change, initially considering calling it "Knoxville Engineer District", but eventually deciding on "''Manhattan Engineer District''" (MED), as the office would at first be in New York, for a non-existent administrative division of the US Army Corps of Engineers. In daily parlance, the [[nickname]] became the ''Manhattan Project''.<ref name=Broad/><ref>Leslie R. Groves, Now it can be told: the story of the Manhattan Project (New York: Harper, 1962), 17.</ref> The Corps Manhattan ''district,'' unlike other regional Corps offices, was not to have territorial limits.
Coordination for the project moved to [[Oak Ridge, Tennessee|Oak Ridge]], [[Tennessee]], in 1943, but the name ''Manhattan Engineer District'' was not changed.
==Discovery of nuclear fission==
{{main|History of physics|History of nuclear weapons|World War II}}
The first decades of the twentieth century led to radical changes in the understanding of the [[physics]] of the atom, including the discovery of the [[nucleus]], the idea of [[radiation]], and the fact that the splitting of atomic nuclei could lead to massive release of energy ([[nuclear fission]]).
By 1932, the atom was thought to consist of a small, dense [[atomic nucleus|nucleus]] containing most of the atom's [[atomic mass|mass]] in the form of [[protons]] and [[neutrons]] and was surrounded by a shell of [[electron]]s. Study on the phenomenon of [[radioactivity]] began with the discovery of uranium ores by [[Henri Becquerel]] in 1896 and was followed by the work of [[Pierre Curie|Pierre]] and [[Marie Curie]] on [[radium]]. Their research seemed to promise that atoms, previously thought to be ultimately stable and indivisible, actually had the potential of containing and releasing immense amounts of energy. In 1919 [[Ernest Rutherford]] achieved the first artificial nuclear disintegrations by bombarding [[nitrogen]] with [[alpha particle]]s emitted from a radioactive source, thus becoming the first person in history to intentionally "split the atom". It had become clear from the Curies' work that there was a tremendous amount of energy locked up in [[radioactive decay]]—far more than chemistry could account for. But even in the early 1930s such illustrious physicists as [[Ernest Rutherford]] and [[Albert Einstein]], could see no way of artificially releasing that energy any faster than nature naturally allowed it to leave. "Radium engines" in the 1930s were the stuff of science fiction, such as was being written at the time by [[Edgar Rice Burroughs]]. [[H. G. Wells]] included air-dropped "atomic bombs" in his 1914 [[novel]] ''[[The World Set Free]]''. Though Wells' "atomic bombs" bore little resemblance to actual nuclear weapons (they were simply regular bombs that never stopped exploding), [[Leó Szilárd]] later commented that this story influenced his later research into this subject.
Progress in controlling and understanding nuclear fission accelerated in the 1930s when further manipulation of the nuclei of atoms became possible. In 1932, Sir [[John Cockcroft]] and [[Ernest Walton]] were first to "split the atom" (cause a nuclear reaction) by using artificially accelerated particles. In 1934, [[Irène Joliot-Curie|Irène]] and [[Frédéric Joliot-Curie]] discovered that artificial [[radioactivity]] could be induced in stable elements by bombarding them with alpha particles. The same year [[Enrico Fermi]] reported similar results when bombarding uranium with [[neutron]]s (discovered in 1932), but he did not immediately appreciate the consequences of his results.
In December 1938, the <!-- Q: Should this be a link? A: YES, because the geopolitical situation is highly relevant to this article. -->[[Germany|Germans]] [[Otto Hahn]] and [[Fritz Strassmann]] published experimental results about bombarding uranium with neutrons. They showed that it produced an isotope of [[barium]]. Shortly after, their Austrian co-worker [[Lise Meitner]] (a political refugee in [[Sweden]] at the time) and her nephew [[Otto Robert Frisch]] correctly interpreted the results as the splitting of the uranium nucleus after the absorption of a neutron—nuclear fission—which released a large amount of [[binding energy|energy]] and additional neutrons. A direct experimental evidence of the nuclear fission was performed by Frisch, following a fundamental idea suggested to him by [[George Placzek]] <ref>Frisch O. R.: "The Discovery of Fission—How It All Began". Physics Today 20 (1967), 11, pp. 43–48. Wheeler J. A.: "Mechanism of Fission". Physics Today 20 (1967), 11, pp. 49–52 </ref>.
In 1933, [[Hungary|Hungarian]] physicist [[Leó Szilárd]] had proposed that if ''any'' neutron-driven process released more neutrons than those required to start it, an expanding [[nuclear chain reaction]] might result. Chain reactions were familiar as a phenomenon from chemistry (where they typically caused explosions and other run-away reactions), but Szilárd was proposing them for a ''nuclear'' reaction, for the first time. However, Szilárd had proposed to look for such reactions in the lighter atoms, and nothing of the sort was found. Upon [[experimentation]] shortly after the uranium fission discovery, Szilárd found that the fission of uranium released two or more neutrons on average, and immediately realized that a nuclear chain reaction by this mechanism was possible in theory. Szilárd kept this secret at first because he feared its use as a weapon by [[fascism|fascist]] governments. He convinced others to do so, but identical results were soon published by the Joliot Curie group, to his great dismay.
That such mechanisms might have implications for civilian power or military weapons was perceived by numerous scientists in many countries, around the same time. While these developments in science were occurring, many political changes were happening in [[Europe]]. [[Adolf Hitler]] was appointed chancellor of Germany in January 1933. His [[Anti-Semitism|anti-Semitic]] ideology caused all [[Jewish]] civil servants, including many physicists, to be [[Racial policy of Nazi Germany|fired from their posts]]. Consequently many European physicists who later made key discoveries went into exile in the [[United Kingdom]] and the [[United States]]. After [[Nazi Germany]] invaded [[Poland]] in 1939 and [[World War II]] began, many scientists in the United States and the United Kingdom became anxious about what Germany might do with [[nuclear technology]]. [[Albert Einstein]] in particular wrote several letters to [[Franklin Roosevelt]] urging him to establish the nuclear capability before the Germans. These letters, especially one called the [[Einstein-Szilárd letter]] (written in August 1939, but not personally received by Roosevelt until October 1939), were influential in the acceleration of the project{{who}}.
==Acceleration of the Project==
[[Image:JROppenheimer-LosAlamos.jpg|right|thumb|A few months after he was put in charge of fast neutron research, Berkeley physicist [[J. Robert Oppenheimer]] convened a conference on the topic of [[nuclear weapon design]].]]
Having begun to wrest control of the uranium research from the [[National Bureau of Standards]], the project leaders began to accelerate the bomb project under the [[Office of Scientific Research and Development|OSRD]]. [[Arthur Compton]] organized the [[University of Chicago Metallurgical Laboratory]] in early 1942 to study [[plutonium]] and [[fission piles]] (primitive [[nuclear reactor]]s), and asked theoretical physicist [[Robert Oppenheimer]] of the [[University of California, Berkeley]] to take over research on fast neutron calculations—key to calculations about critical mass and weapon detonation—from [[Gregory Breit]]. [[John H. Manley|John Manley]], a physicist at the Metallurgical Laboratory, was assigned to help Oppenheimer find answers by coordinating and contacting several experimental physics groups scattered across the country.
During the spring of 1942, Oppenheimer and [[Robert Serber]] of the [[University of Illinois at Urbana-Champaign|University of Illinois]] worked on the problems of neutron diffusion (how neutrons moved in the chain reaction) and [[hydrodynamics]] (how the explosion produced by the chain reaction might behave). To review this work and the general theory of fission reactions, Oppenheimer convened a summer study at the University of California, Berkeley, in June 1942. Theorists [[Hans Bethe]], [[John Van Vleck]], [[Edward Teller]], [[Felix Bloch]], [[Emil Konopinski]], [[Robert Serber]], [[Stanley S. Frankel]], and [[Eldred C. Nelson]] (the latter three all former students of Oppenheimer) quickly confirmed that a fission bomb was feasible.
There were still many unknown factors in the development of a nuclear bomb, however, even though it was considered to be theoretically possible. The properties of pure uranium-235 were still relatively unknown, as were the properties of plutonium, a new element which had only been discovered in February 1941 by [[Glenn Seaborg]] and his team. Plutonium was the product of uranium-238 absorbing a neutron which had been emitted from a fissioning uranium-235 atom, and was thus able to be created in a nuclear reactor. But at this point no reactor had yet been built, so while plutonium was being pursued as an additional fissile substance, it was not yet to be relied upon. Only microgram quantities of plutonium existed at the time (produced from neutrons derived from reaction started in a cyclotron).
[[Image:Los Alamos Primer assembly methods.png|right|thumb|A number of the different fission bomb assembly methods explored during the summer 1942 conference, later reproduced as drawings in ''[[The Los Alamos Primer]]''. In the end, only the "gun" method (at top) and a more complicated variation of the "implosion" design would be used. At the bottom are "autocatalytic method" designs.]]
The scientists at the Berkeley conference determined that there were many possible ways of arranging the fissile material into a critical mass, the simplest being the shooting of a "cylindrical plug" into a sphere of "active material" with a "tamper"—dense material which would focus neutrons inward and keep the reacting mass together to increase its efficiency (this model "avoids fancy shapes", Serber would later write).<ref>Serber, Robert. ''[[The Los Alamos Primer]]'' (Los Alamos Report LA-1, compiled April 1943, [[declassified]] 1965): p. 21.</ref> They also explored designs involving [[spheroid]]s, a primitive form of "implosion" (suggested by [[Richard C. Tolman]]), and explored the speculative possibility of "[[Autocatalysis|autocatalytic]] methods" which would increase the efficiency of the bomb as it exploded.
Considering the idea of the fission bomb theoretically settled until more experimental data were available, the conference then turned in a different direction. Hungarian physicist Edward Teller pushed for discussion on an even more powerful bomb: the "Super", which would use the explosive force of a detonating fission bomb to ignite a [[nuclear fusion|fusion]] reaction in [[deuterium]] and [[tritium]]. This concept was based on studies of energy production in stars made by Hans Bethe before the war, and suggested as a possibility to Teller by [[Enrico Fermi]] not long before the conference. When the detonation wave from the fission bomb moved through the mixture of [[deuterium]] and [[tritium]] nuclei, these would fuse together to produce much more energy than fission could. But Bethe was skeptical. As Teller pushed hard for his "superbomb"—now usually referred to as a "hydrogen bomb"—proposing scheme after scheme, Bethe refuted each one. The fusion idea had to be put aside in order to concentrate on actually producing fission bombs.
Teller also raised the speculative possibility that an atomic bomb might "ignite" the atmosphere, because of a hypothetical fusion reaction of nitrogen nuclei. Bethe calculated, according to Serber, that it could not happen. In his book ''The Road from Los Alamos'', Bethe says a refutation was written by Konopinski, C. Marvin, and Teller as report LA-602, showing that ignition of the atmosphere was impossible, not just unlikely.<ref> (Konopinski, C. Marvin, and Teller, Report LA-602, declassified Feb. 1973, [http://www.fas.org/sgp/othergov/doe/lanl/docs1/00329010.pdf PDF]</ref> In Serber's account, Oppenheimer mentioned it to Arthur Compton, who "didn't have enough sense to shut up about it. It somehow got into a document that went to Washington" which led to the question being "never laid to rest".<ref>In Bethe's account, the possibility of this ultimate catastrophe came up again in 1975 when it appeared in a magazine article by H. C. Dudley, who got the idea from a report by [[Pearl Buck]] of an [[interview]] she had with [[Arthur Compton]] in 1959. The worry was not entirely extinguished in some people's minds until the [[Trinity test]].</ref>
The conferences in the summer of 1942 provided the detailed theoretical basis for the design of the atomic bomb, and convinced Oppenheimer of the benefits of having a single centralized laboratory to manage the research for the bomb project, rather than having specialists spread out at different sites across the United States.
==Project sites==
Though it involved over thirty different research and production sites, the Manhattan Project was largely carried out at three secret scientific cities that were established by power of [[eminent domain]]: [[Los Alamos, New Mexico]]; [[Oak Ridge, Tennessee]]; and [[Richland, Washington]]. The Tennessee site was chosen for the vast quantities of cheap hydroelectric power already available there (due to the [[Tennessee Valley Authority]]) necessary to produce uranium-235 in giant ion separation magnets. The [[Hanford Site]] near Richland, Washington, was chosen for its location near [[Columbia River|a river]] that could supply water to cool the reactors which would produce the plutonium. All the sites were suitably far from coastlines and therefore less vulnerable to possible enemy attack from Germany or Japan.
The [[Los Alamos National Laboratory]] was built on a mesa that previously hosted the [[Los Alamos Ranch School]], a private school for teenage boys. The site was chosen primarily for its remoteness. Oppenheimer had known of it from his horse-riding near his ranch in New Mexico, and he showed it as a possible site to the government representatives, who promptly bought it for $440,000. In addition to being the main "think-tank", Los Alamos was responsible for final assembly of the [[bomb]]s, mainly from materials and components produced by other sites. Manufacturing at Los Alamos included casings, explosive lenses, and fabrication of fissile materials into [[bomb cores]].
Oak Ridge facilities covered more than 60,000 acres (243 km²) of several former farm communities in the [[Tennessee Valley]] area. Some Tennessee families were given two weeks' notice to vacate family farms that had been their home for generations. So secret was the site during WW2 that the state governor was unaware that Oak Ridge (which was to become the fifth largest city in the state) was being built. At one point Oak Ridge plants were consuming 1/6th of the electrical power produced in the U.S., more than [[New York City]]. Oak Ridge mainly produced uranium-235.
The Hanford Site, which grew to almost 1,000 square miles (2,600 km²), took over [[irrigated farm land]], [[fruit orchard]]s, a [[railroad]], and two farming communities, [[Hanford, Washington|Hanford]] and [[White Bluffs, Washington|White Bluffs]], in a sparsely populated area adjacent to the [[Columbia River]]. Hanford hosted nuclear reactors cooled by the [[river]] and was the plutonium production center.
The existence of these sites and the secret cities of Los Alamos, Oak Ridge, and Richland were not made public until the announcement of the Hiroshima explosion, and the sites remained secret until after the end of WWII.
The project originally was headquartered at 270 Broadway in [[Manhattan]]. Other offices were scattered throughout the city. <ref>[http://www.nytimes.com/interactive/2007/10/30/science/20071030_MANHATTAN_GRAPHIC.html "The Manhattan Project"], nytimes.com, accessed [[Nov 2]], [[2007]].</ref> The Broadway headquarters lasted little more than a year before it was moved in 1943, although many of the other offices in Manhattan remained.<ref> [http://www.nytimes.com/2007/10/30/science/30manh.html?_r=2&ref=science&oref=slogin&oref=slogin Why They Called It the Manhattan Project], nytimes.com, accessed [[Nov 2]], [[2007]].</ref>
[[Image:Manhattan Project US Map.png|thumb|center|600px|A selection of U.S. sites important to the Manhattan Project.]]
Major Manhattan Project sites and subdivisions included:
*[[Site W]] ([[Hanford, Washington]]): a plutonium production facility (now [[Hanford Site]])
*[[Site X]] ([[Oak Ridge, Tennessee]]): enriched uranium production and plutonium production research (now [[Oak Ridge National Laboratory]]) Site X also included:
**[[X-10 Graphite Reactor]]: graphite reactor research pilot plant (on the site of what is now Oak Ridge National Laboratory)
**[[Y-12 National Security Complex|Y-12]]: electromagnetic separation uranium enrichment plant
**[[K-25]]: gaseous diffusion uranium enrichment plant
**[[S-50]]: thermal diffusion uranium enrichment plant
*[[Site Y]] ([[Los Alamos, New Mexico]]): a bomb research laboratory (now [[Los Alamos National Laboratory]])
*[[Metallurgical Laboratory]] ([[Chicago]], [[Illinois]]): reactor development (now [[Argonne National Laboratory]])
*[[Project Alberta]] ([[Wendover, Utah]] and [[Tinian]]): preparations for the combat delivery of the bombs
*[[Project Ames]] ([[Ames, Iowa]]): production of raw uranium metal (now [[Ames Laboratory]])
*[[Dayton Project]] ([[Dayton, Ohio]]): research and development of polonium refinement and industrial production of polonium for atomic bomb triggers
*[[Project Camel]] ([[Inyokern, California]]): high explosives research and non-nuclear engineering for the [[Fat Man]] bomb
*[[Trinity test|Project Trinity]] ([[Alamogordo, New Mexico]]): preparations for the testing of the first atomic bomb
*[[Lawrence Berkeley National Laboratory|Radiation Laboratory]] ([[Berkeley, California]]): electromagnetic separation enrichment research (now [[Lawrence Berkeley National Laboratory]])
*Project '9' ([[Trail, British Columbia]]): [[heavy water]] ([[deuterium]]) production.<ref>{{cite paper
| title =An Early History of Heavy Water
| author =Chris Waltham
| publisher =Department of Physics and Astronomy, University of British Columbia
| date = [[20 June]] [[2002]]
| url =http://arxiv.org/pdf/physics/0206076.pdf
| format =PDF
}}</ref>
==Need for coordination==
{{Citations missing|date=April 2008}}
The measurements of the interactions of [[fast neutron]]s with the materials in a bomb were essential because the number of neutrons produced in the fission of uranium and plutonium must be known, and because the substance surrounding the nuclear material must have the ability to [[neutron reflector|reflect]], or scatter, neutrons back into the chain reaction before it is blown apart in order to increase the energy produced. Therefore, the [[neutron scattering]] properties of materials had to be measured to find the best reflectors.
Estimating the explosive power required knowledge of many other nuclear properties, including the [[Cross section (physics)|cross section]] (a measure of the probability of an encounter between particles that result in a specified effect) for nuclear processes of neutrons in uranium and other elements. Fast neutrons could only be produced in [[particle accelerator]]s, which were still relatively uncommon instruments in 1942.
The need for better coordination was clear. By September 1942, the difficulties in conducting studies on nuclear weapons at universities scattered throughout the country indicated the need for a laboratory dedicated solely to that purpose. A greater need was the construction of industrial plants to produce uranium-235 and plutonium—the fissionable materials to be used in the weapons.
[[Vannevar Bush]], the head of the civilian [[Office of Scientific Research and Development]] (OSRD), asked President Roosevelt to assign the operations connected with the growing nuclear weapons project to the military. Roosevelt chose the Army to work with the OSRD in building production plants. The [[Army Corps of Engineers]] selected [[Col. James Marshall]] to oversee the construction of factories to separate uranium isotopes and manufacture plutonium for the bomb.
Marshall and his deputy, Col. [[Kenneth Nichols]], struggled to understand the proposed processes and the scientists with whom they had to work. Thrust into the new field of nuclear physics, they felt unable to distinguish between technical and personal preferences. Although they decided that a site near [[Knoxville, Tennessee]], would be suitable for the first production plant, they did not know how large the site needed to be and delayed its acquisition.
Because of its experimental nature, the nuclear weapons work could not compete with the Army's more urgent tasks for priority. The scientists' work and production plant construction often were delayed by Marshall's inability to obtain critical materials, such as [[steel]], needed in other military projects.
Even selecting a name for the project was difficult. The title chosen by Gen. [[Brehon B. Somervell]], "Development of Substitute Materials," was objectionable because it seemed to reveal too much.
==Manhattan Engineer District==
[[Image:Groves Oppenheimer.jpg|right|thumb|upright|General [[Leslie Groves]] (''left'') was appointed the military head of the Manhattan Project, while [[Robert Oppenheimer]] (''right'') was the scientific director.]]
Vannevar Bush became dissatisfied with Col. James Marshall's failure to get the project moving forward expeditiously and made this known to Secretary of War Stimson and Army Chief of Staff George Marshall. Marshall then directed General Somervell to replace Col. Marshall with a more energetic officer as director. In the summer of 1942, Col. [[Leslie Groves]] was deputy to the chief of construction for the Army Corps of Engineers and had overseen the very rapid construction of [[the Pentagon]], the world's largest office building. He was widely respected as an intelligent, hard driving, though brusque officer who got things done in a hurry. Hoping for an overseas command, Groves vigorously objected when Somervell appointed him to the weapons project. His objections were overruled, and Groves resigned himself to leading a project he thought had little chance of success. Groves appointed Oppenheimer as the project's scientific director, to the surprise of many. (Oppenheimer's radical political views were thought to pose security problems). However, Groves was convinced Oppenheimer was a genius who could talk about and understand nearly anything, and he was convinced such a man was needed for a project such as the one being proposed.
Groves renamed the project '''The Manhattan Engineer District'''. The name evolved from the Corps of Engineers practice of naming districts after its headquarters' city (Marshall's headquarters were in New York City). At that time, Groves was promoted to [[brigadier general]], giving him the rank necessary to deal with senior scientists in the project.
Within a week of his appointment, Groves had solved the Manhattan Project's most urgent problems. His forceful and effective manner was soon to become all too familiar to the atomic scientists.
The first major scientific hurdle of the project was solved on [[December 2]], [[1942]], beneath the [[bleachers]] of [[Stagg Field]] at the University of Chicago, where a team led by [[Enrico Fermi]], for whom [[Fermilab]] is named, initiated the first artificial <ref>Natural self-sustaining nuclear reactions have occurred in the distant past (circa two billion years ago); see [[Natural nuclear fission reactor]]</ref> self sustaining nuclear chain reaction in an experimental [[nuclear reactor]] named [[Chicago Pile-1]]. A coded phone call from Compton saying, "The [[Italy|Italian]] [[navigator]] [referring to Fermi] has landed in the new world, the natives are friendly" to Conant in [[Washington, D.C.]], brought news of the experiment's success.
==Uranium bomb==
[[Image:Gun-type fission weapon en-labels thin lines.svg|thumb|right|A gun-type nuclear bomb.]]
The [[Hiroshima]] bomb, [[Little Boy]], was made from uranium-235, a rare [[isotope]] of uranium that has to be [[isotope separation|physically separated]] from the more plentiful uranium-238 isotope, which is not suitable for use in an explosive device. Since U-235 is only 0.7% of raw uranium and is chemically identical to the 99.3% of U-238, various physical methods were considered for separation. Most of the [[uranium enrichment]] work was performed at Oak Ridge.
[[Image:Calutrons at Oak Ridge.jpg|thumb|left|upright|Control panels and operators for [[calutron]]s at the [[Y-12 National Security Complex|Y-12 Plant]] in [[Oak Ridge National Laboratory|Oak Ridge, Tennessee]].]]
One method of separating uranium 235 from raw uranium ore was devised by [[Francis Simon|Franz Simon]] and [[Nicholas Kurti]], two Jewish émigrés, at [[University of Oxford|Oxford University]]. Their method using [[gaseous diffusion]] was scaled up in a [[K-25|large separation plant]] at Oak Ridge, using [[uranium hexafluoride]] ([[Uranium|U]][[Fluorine|F]]<sub>6</sub>) gas as the process fluid. During the war this method was important primarily for producing partly enriched material to feed the electromagnetic separation process undertaken in calutrons (see below).
Another method—[[electromagnetic isotope separation]]—was developed by [[Ernest Lawrence]] at the [[University of California Radiation Laboratory]] at the [[University of California, Berkeley]]. This method was implemented in Oak Ridge at the [[Y-12 Plant]], employing devices known as [[calutron]]s, which were effectively [[mass spectrometer]]s. [[Copper]] was originally intended for electromagnet coils, but there was an insufficient amount available due to war shortages. The project engineers were forced to borrow [[silver]] from the [[U.S. Treasury]]. A total of 70,000,000 pounds of silver from the U.S. Treasury reserves was used for coils, and was returned after the project ended. Initially the method seemed promising for large scale production but was expensive and produced insufficient material and was later abandoned after the war.
Other techniques were also tried, such as thermal diffusion and the use of high-speed centrifuges. Thermal diffusion was not used to produce highly-enriched uranium, but was used during the war in the [[S-50]] facility to begin enrichment of the uranium, and its product was passed as the feed into the other facilities.
The uranium bomb was a [[gun-type fission weapon]]. One mass of U-235, the "bullet," is fired down a more or less conventional [[gun barrel]] into another mass of U-235, rapidly creating the critical mass of U-235, resulting in an explosion. The method was so certain to work that no test was carried out before the bomb was dropped over [[Hiroshima]], though extensive laboratory testing was undertaken to make sure the fundamental assumptions were correct. Also, the bomb dropped used all the existing extremely highly purified U-235 (and even most of the highly purified material) so there was no U-235 available for such a test anyway. The bomb's design was known to be inefficient and prone to accidental discharge. It has been estimated that only about 15% of the fissile material went critical. {{Fact|date=June 2008}}
==Plutonium bomb==
[[Image:Implosion Nuclear weapon.svg|right|thumb|The basic concept of an implosion-style nuclear weapon. Actual pictures and details of the bomb's inner workings remain classified.]]
The bombs used in the first test at [[Trinity Site]] on [[July 16]] [[1945]], in New Mexico ([[the gadget]] of the [[Trinity test]]), and in the [[Nagasaki, Nagasaki|Nagasaki]] bomb, [[Fat Man]], were made primarily of plutonium-239, a synthetic element.
Although uranium-238 is useless as fissile isotope for an atomic bomb, U-238 is used to produce plutonium. The fission of U-235 produces relatively slow neutrons which are absorbed by U-238, which after a few days of decay turns into plutonium-239. The production and purification of plutonium used techniques developed in part by [[Glenn Seaborg]] while working at Berkeley and Chicago. Beginning in 1943, huge plants were built to produce plutonium at the [[Hanford Site]].
[[Image:Fat man.jpg|left|thumb|A mock-up of the plutonium bomb, Fat Man]]
From 1943–1944, development efforts were directed to a [[gun-type fission weapon]] with plutonium, called "[[Thin Man bomb|Thin Man]]". Once this was achieved, the uranium version "Little Boy" would require a relatively simple adaptation, it was thought.
Initial tests of the properties of plutonium were done using [[cyclotron]]-generated plutonium-239, very pure but in very small amounts. On [[April 5]] [[1944]], [[Emilio Segrè]] at Los Alamos received the first sample of Hanford-produced plutonium. Within ten days, he discovered a fatal flaw: reactor-bred plutonium was far less isotopically pure than cyclotron-produced plutonium, and as a result had a much higher spontaneous fission rate than uranium-235. The unwanted isotope responsible for this high fission rate was plutonium-240, formed from plutonium-239 by capture of an additional neutron. Unlike the cyclotron, the plutonium breeding reactors had a much higher [[neutron flux]] and thus yielded an increased proportion of plutonium-240. Plutonium-240 was even harder to separate from plutonium-239 than U-235 was to separate from U-238, so there was no question of doing so. The contaminating Pu-240 had to stay in the plutonium metal used in the bomb, where its spontaneous fissions were a source of unwanted neutrons. The implications of this made a "gun" detonation mechanism unsuitable. Because of the relatively slow speed of the gun device, "early" neutrons from spontaneously fissioning Pu-240 would start the reaction before the device was fully assembled by the gun process, and as a result, a plutonium bomb would "fizzle" (that is, heat up and blow itself apart) before it could be turned into a shape suitable for an efficient chain reaction which would split a substantial amount of the plutonium. Even a 1% fission of the material would result in a workable bomb, almost a thousand times more powerful than conventional bombs for the weight; but a fizzle promised far less even than this.
In July 1944, the decision was made to cease work on the plutonium gun method. There would be no "Thin Man." The gun method was further developed for uranium only, which had few complications. Most efforts were then directed to a different method for plutonium.
[[Image:Thin Man plutonium gun bomb casings.jpg|right|thumb|In July 1944 the Los Alamos laboratory abandoned the plutonium gun-type bomb ("[[Thin Man (bomb)|Thin Man]]", ''shown above'') and focused almost entirely on the problem of implosion. (The Fat Man casing is also visible in the photo background.)]]
Ideas of using alternative detonation schemes had existed for some time at Los Alamos. One of the more innovative had been the idea of "implosion"—a sub-critical sphere of fissile material could, using chemical explosives, be forced to collapse in on itself, creating a very dense critical mass, which because of the very short distances the metal needed to travel to make it, would come into existence for a far shorter time than it would take to assemble a mass from a bullet. Initially, implosion had been entertained as a possible, though unlikely method. However, after it was discovered that it was the only possible solution for using reactor-bred plutonium, and that uranium-235 production could not be substantially increased, the implosion project received the highest priority, as the only solution to scaling up fissionable material production to the level needed for multiple bombs. By the end of July 1944, the entire project had been reorganized around solving the implosion problem. It eventually involved using [[shaped charge]]s with many explosive lenses to produce the perfectly spherical explosive wave needed to properly compress the plutonium sphere.
Because of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, an initial test would be required. The first [[nuclear test]] took place on [[July 16]] [[1945]], near [[Alamogordo]], [[New Mexico]], under the supervision of Groves's deputy Brig. Gen. [[Thomas Farrell]]. This test was dubbed by Oppenheimer "[[Trinity test|Trinity]]".
==Similar efforts==
A similar effort was undertaken in the [[Soviet Union|USSR]] in September 1941 headed by [[Igor Kurchatov]] (with some of Kurchatov's World War II knowledge coming secondhand from Manhattan Project countries, thanks to spies, including at least two on the scientific team at Los Alamos, [[Klaus Fuchs]] and [[Theodore Hall]], unknown to each other).
After the MAUD Committee's report, the British and Americans exchanged nuclear information but initially did not pool their efforts. A British project, code-named [[Tube Alloys]], was started but did not have American resources. Consequently the British bargaining position worsened, and their motives were mistrusted by the Americans. Collaboration therefore lessened markedly until the [[Quebec Agreement]] of August 1943, when a large team of British, Canadian and Australian scientists joined the Manhattan Project.
[[Image:German Experimental Pile - Haigerloch - April 1945.jpg|thumb|left|''The German experimental [[nuclear pile]] at [[Haigerloch]]'']]
The question of [[Axis Powers|Axis]] efforts on the bomb has been a contentious issue for historians. It is believed that efforts undertaken in Germany, headed by [[Werner Heisenberg]], and in [[Japanese atomic program|Japan]], were also undertaken during the war with little progress. It was initially feared that [[Hitler]] was very close to developing his own bomb. Many German scientists in fact expressed surprise to their Allied captors when the bombs were detonated in Japan. They were convinced that talk of atomic weapons was merely propaganda. However, Werner Heisenberg (by then imprisoned in England at [[Farm Hall]] with several other nuclear project physicists) almost immediately figured out what the Allies had done, explaining it to his fellow scientists (and hidden microphones) within days. The Nazi reactor effort had been severely handicapped by Heisenberg's belief that [[heavy water]] was necessary as a [[neutron moderator]] (slowing preparation material) for such a device. The Germans were short of heavy water throughout the war because of Allied efforts to prevent Germany from obtaining it, and the Germans never did stumble on the secret of purified graphite for making nuclear reactors from natural uranium.
Bohr, Heisenberg and Fermi were all colleagues who were key figures in developing the [[quantum physics|quantum theory]] together with [[Wolfgang Pauli]], prior to the war. They had known each other well in Europe and were friends. [[Niels Bohr]] and Heisenberg even discussed the possibility of the atomic bomb prior to and during the war, before the United States became involved. Bohr recalled that Heisenberg was unaware that the [[supercritical mass]] could be achieved with U-235, and both men gave differing accounts of their conversations at this sensitive time. Bohr at the time did not trust Heisenberg, and never quite forgave him for his decision not to flee Germany before the war when given the chance. Heisenberg, for his part, seems to have thought he was proposing to Bohr a mutual agreement between the two sides not to pursue nuclear technology for destructive purposes. If so, Heisenberg's message did not get through. Heisenberg, to the end of his life, maintained that the partly-built German heavy-water nuclear reactor found after the war's end in his lab was for research purposes only, and a full bomb project had not been contemplated (there is no evidence to contradict this, but by this time late in the war, Germany was far from having the resources for a Hanford-style plutonium bomb, even if its scientists ''had'' decided to pursue one and had known how to do it).
Together with the [[cryptography|cryptographic]] efforts centered at [[Bletchley Park]] and also at [[Arlington Hall]], the development of [[radar]] and [[computers]] in the UK and later in the US, and the [[jet engine]] in the UK and Germany, the Manhattan Project represents one of the few massive, secret and outstandingly successful technological efforts spawned by the conflict of World War II.
==See also==
{{WorldWarIISegmentUnderInfoBox}}
{{portal|World War II|Heinkel_He_111_during_the_Battle_of_Britain.jpg}}
{{Historyportal}}
*[[Timeline of the Manhattan Project]]
*August 1945
** [[Atomic bombings of Hiroshima and Nagasaki]]
** [[Smyth Report]]
*Related locations
** [[Hanford Site]] (plutonium production)
** [[Ames Laboratory]] (uranium production from ores)
** [[Los Alamos National Laboratory]] (secret weapons lab)
** [[Lawrence Livermore National Laboratory]] (second weapons lab, created in 1950s)
** [[Metallurgical Laboratory]] (first controlled nuclear chain reaction)
** [[Oak Ridge, Tennessee]]
*** [[Oak Ridge National Laboratory]] (site of graphite reactor and pilot facilities for plutonium production)
*** [[Y-12]] (uranium enrichment)
*** [[K-25]] (uranium enrichment)
** [[Trinity site]] (first nuclear test)
** [[Trail, British Columbia]] (''Project 9'', [[heavy water]] plant)
*Nuclear weapons
** [[History of nuclear weapons]]
** [[Nuclear arms race]]
** [[Nuclear weapon]]
** [[Nuclear weapon design]]
** [[Isotope separation]] (necessary for uranium enrichment)
** [[List of countries with nuclear weapons]]
** [[The United States and nuclear weapons]]
*People
** [[:Category:Manhattan Project people]] (lists articles about people involved in the project)
** [[Lise Meitner]] and [[Otto Hahn]], discoverers of [[Nuclear fission|fission]]
** [[David Bohm]], did work that was immediately classified, that he then wasn't allowed to read
*Other projects
** [[Operation Alsos]], and [[German nuclear energy project]]
** [[Japanese atomic program]]
** [[Soviet atomic bomb project]]
** [[Tube Alloys]] (British WWII atomic program)
*Movies, in chronological order:
** ''[[Above and Beyond]]'' (1952), a film related to the project, centered on Col [[Paul Tibbets]], pilot of the plane which dropped the Hiroshima bomb
** ''[[Kiss Me Deadly]]'' (1955), a [[film noir]] only tangentially related to the Manhattan Project
** ''[[The Day After Trinity]]'' (1981), a documentary about the project.
** ''[[Day One (film)|Day One]]'' (1989), a film about the project in a political perspective
** ''[[Fat Man and Little Boy]]'' (1989), Hollywood drama based on the project staring [[Paul Newman]]
**''[[White Light/Black Rain: The Destruction of Hiroshima and Nagasaki]]'' (2007)
*Music
** [[Manhattan Project (song)|Manhattan Project]] by [[Rush (band)|Rush]]
** Brighter Than A Thousand Suns by [[Iron Maiden (band)|Iron Maiden]]
** ''[[Doctor Atomic]]'', an opera by [[John Coolidge Adams]] with libretto by [[Peter Sellars]]
*Entertainment
**The main character of the game [[Freedom Force]] , Minuteman, was a scientist for the Manhattan Project
**[[3D Realms]](originally Apogee) released a video game entitled "[[Duke Nukem: Manhattan Project]]" for PC in 2002.
**[[Dr. Manhattan]], a superhero from the graphic novel ''[[Watchmen]]'' named by the US government after the Manhattan Project.
**In the game ''[[Metal Gear Solid]]'', the character [[Otacon_%28Metal_Gear%29#Otacon|Otacon]] claims that his grandfather was involved in the Manhattan Project.
**In the game ''[[Metal Gear Solid 2]]'', the character [[Fat Man_%28Metal_Gear%29#Fat Man|Fat Man]] is named after the bomb dropped in Nagasaki, Japan.
**In the game ''[[Civilization Revolution]]'', the player can research the Manhattan Project resulting in the creation of an atomic bomb which the player can use against his enemies.
==Notes==
{{reflist}}
==References==
;Overall, administrative, and diplomatic histories of the Manhattan Project
*DeGroot, Gerard, "The Bomb: A History of Hell on Earth", London: Pimlico, 2005. ISBN 0-7126-7748-8
*[[Leslie Groves|Groves, Leslie]]. ''Now it Can be Told: The Story of the Manhattan Project.'' New York: Harper, 1962. ISBN 0-306-70738-1
*Herken, Gregg. ''Brotherhood of the Bomb : The Tangled Lives and Loyalties of Robert Oppenheimer, Ernest Lawrence, and Edward Teller.'' New York: Henry Holt and Co., 2002. ISBN 0-8050-6588-1
*[[Richard G. Hewlett|Hewlett, Richard G.]], and Oscar E. Anderson. ''The New World, 1939-1946.'' University Park: Pennsylvania State University Press, 1962.
*Howes, Ruth H. and Herzenberg, Caroline L. ''Their Day in the Sun: Women of the Manhattan Project.'' Philadelphia: Temple University Press, 1999. ISBN 1-56639-719-7
*[[Robert Jungk|Jungk, Robert]], ''Brighter Than a Thousand Suns: A Personal History of the Atomic Scientists'', (NY: Harcourt, Brace, 1956, 1958)
*Norris, Robert S., "Racing for the Bomb: General Leslie R. Groves, The Manhattan Project's Indispensable Man". Vermont: Steerforth Press, First Paperback edition, 2002. ISBN 1-58642-067-4.
*[[Richard Rhodes|Rhodes, Richard]]. ''The Making of the Atomic Bomb''. New York: Simon & Schuster, 1986. ISBN 0-671-44133-7
* Rhodes, Richard. ''Dark Sun: The Making of the Hydrogen Bomb.'' New York: Simon & Schuster, 1995. ISBN 0-684-80400-X
*[[Richard P. Feynman|Feynman, Richard P.]] ''Surely you're joking, Mr. Feynman'' W. W. Norton & Company, 1997. ISBN-13: 978-0393316049
;Technical histories
*Sherwin, Martin J. ''A World Destroyed: The Atomic Bomb and the Grand Alliance.'' New York: Alfred A. Knopf, 1975. ISBN 0-394-49794-5
*Groueff, Stephane. ''Manhattan Project: The Untold Story of the Making of the Atomic Bomb.'' Boston: Little, Brown & Co, 1967.
*Hoddeson, Lillian, Paul W. Henriksen, Roger A. Meade, and Catherine L. Westfall. ''Critical Assembly: A Technical History of Los Alamos During the Oppenheimer Years, 1943–1945.'' New York: Cambridge University Press, 1993. ISBN 0-521-44132-3
*[[Robert Serber|Serber, Robert]]. ''The Los Alamos Primer: The First Lectures on How to Build an Atomic Bomb.'' Berkeley: University of California Press, 1992. ISBN 0-520-07576-5—Original 1943, Los Alamos Report "LA-1", declassified in 1965. (Available on [[commons:Image:Los Alamos Primer.pdf|Wikimedia Commons]]).
*[[Henry DeWolf Smyth|Smyth, Henry DeWolf]]. ''Atomic Energy for Military Purposes; the Official Report on the Development of the Atomic Bomb under the Auspices of the United States Government, 1940–1945.'' Princeton: Princeton University Press, 1945. See [[Smyth Report]].
*Yenne, William. "The Manhattan Project," ''Secret Weapons of World War II: The Techno-Military Breakthroughs That Changed History''. New York: Berkley Books, 2003. 2-7.
;Participant accounts
*Badash, Lawrence, Joseph O. Hirschfelder, Herbert P. Broida, eds. ''Reminiscences of Los Alamos, 1943–1945.'' Dordrecht, Boston: D. Reidel, 1980. ISBN 90-277-1097-X
*[[Hans Bethe|Bethe, Hans A]]. ''The Road from Los Alamos.'' New York: Simon and Schuster, 1991. ISBN 0-671-74012-1
*[[Kenneth Nichols|Nichols, Kenneth David]]. ''The Road to Trinity: A Personal Account of How America's Nuclear Policies Were Made.'' New York: William Morrow and Company Inc, 1987. ISBN 0-688-06910-X
*[[Robert Serber|Serber, Robert]]. ''Peace and War: Reminiscences of a Life on the Frontiers of Science.'' New York: Columbia University Press, 1998. ISBN 0-231-10546-0
*[[Stanisław Ulam|Ulam, Stanisław]]. ''Adventures of a Mathematician.'' New York: Charles Scribner's Sons, 1983. ISBN 0-520-07154-9
==External links==
*[http://www.nytimes.com/2007/10/30/science/30manh.html/ Why They Called It the Manhattan Project]
*[http://www.hbo.com/docs/programs/whitelightblackrain/index.html White Light/Black Rain Official Website] (film)
{{Commons|Manhattan Project}}
*[http://www.atomicmuseum.com/tour/manhattanproject.cfm National Atomic Museum - The Manhattan Project]
*[http://www.3rd1000.com/nuclear/cruc18.htm Development of the Atomic Bomb]
*[http://www.pcf.city.hiroshima.jp/peacesite/English/Stage1/1-1E.html Truth of Atomic Bomb : from Hiroshima]
*[http://alsos.wlu.edu/qsearch.aspx?browse=warfare/Manhattan+Project Annotated bibliography for the Manhattan Project from the Alsos Digital Library for Nuclear Issues.]
*[http://www.nuclearfiles.org/menu/key-issues/nuclear-weapons/history/pre-cold-war/manhattan-project/ Nuclear Files.org] Information on the history of the Manhattan Project
*[http://www.atomicarchive.com/History/mp/index.shtml The Manhattan Project: Making the Atomic Bomb] from atomicarchive.com
*[http://www.travelgoat.com/index.php/pages/place/10183.html Profile of 90 Church Street] travelgoat guide to New York City
*[http://www.eh.doe.gov/ohre/roadmap/achre/intro_3.html The Manhattan Project: A New and Secret World of Human Experimentation]
* [http://www.atomicheritage.org Atomic Heritage Foundation] Manhattan Project Historic Preservation
* [http://www.vega.org.uk/video/programme/22 Interview with Joseph Rotblat who worked on the Manhattan Project and left to work for Pugwash.] The Nobel Peace Prize was awarded to both Rotblat and Pugwash. Freeview video provided by the Vega Science Trust.
*{{gutenberg author | id=United_States._Army._Corps_of_Engineers._Manhattan_District | name=United States Army - Corps of Engineers (Manhattan District)}}
* ''[http://www.randomhouse.com/boldtype/0797/kanon/ Los Alamos]'', a [[murder mystery]] [[novel]] by [[Joseph Kanon]], shows life at the Manhattan Project base.
*[http://www.footnote.com/viewer.php?image=4346693 Notebook recording the first controlled nuclear chain reaction] (includes "We're cookin!" note at the bottom of the page)
*[http://hypertextbook.com/eworld/einstein.shtml Albert Einstein's Letters to President Franklin Delano Roosevelt.]
{{Manhattan Project|state=open}}
[[Category:Atomic bombings of Hiroshima and Nagasaki]]
[[Category:Manhattan Project]]
[[Category:Military projects]]
[[Category:Nuclear weapons of the United States]]
[[Category:Nuclear weapons program of the United States]]
[[Category:Secret military programs]]
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