Манхэттен жобасы: Атом бомбасын жасау тарихы

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The Manhattan Project was a research and development project that produced the first atomic bombs during World War II. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually became the codename for the entire project. Along the way, the project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion (about $ in dollars). Over 90% of the cost was for building factories and producing the fissionable materials, with less than 10% for development and production of the weapons. Two types of atomic bombs were developed during the war. A relatively simple gun type fission weapon was made using uranium 235, an isotope that makes up only 0.7 percent of natural uranium. Since it is chemically identical to the most common isotope, uranium 238, and has almost the same mass, it proved difficult to separate. Three methods were employed for uranium enrichment: electromagnetic, gaseous and thermal. Most of this work was performed at Oak Ridge, Tennessee. In parallel with the work on uranium was an effort to produce plutonium. Reactors were constructed at Oak Ridge and Hanford, Washington, in which uranium was irradiated and transmuted into plutonium. The plutonium was then chemically separated from the uranium. The gun type design proved impractical to use with plutonium so a more complex implosion type nuclear weapon was developed in a concerted design and construction effort at the project's principal research and design laboratory in Los Alamos, New Mexico. The following is a timeline of the Manhattan Project. It includes a number of events prior to the official formation of the Manhattan Project, and a number of events after the atomic bombings of Hiroshima and Nagasaki, until the Manhattan Project was formally replaced by the Atomic Energy Commission in 1947.

August 2: Albert Einstein signs the letter (Einstein–Szilárd letter), authored by physicist Leó Szilárd and addressed to President Franklin D. Roosevelt, advising him to fund research into the possibility of using nuclear fission as a weapon as Nazi Germany may also be conducting such research. September 3: Great Britain and France declare war on Nazi Germany in response to its invasion of Poland, beginning World War II. October 11: Economist Alexander Sachs meets with President Roosevelt and delivers the Einstein–Szilárd letter. Roosevelt authorizes the creation of the Advisory Committee on Uranium. October 21: First meeting of the Advisory Committee on Uranium, headed by Lyman Briggs of the National Bureau of Standards; $6,000 is budgeted for neutron experiments.

March 2: John R. Dunning's team at Columbia University verifies Niels Bohr's hypothesis that uranium 235 is responsible for fission by slow neutrons. March: University of Birmingham based scientists Otto Frisch and Rudolf Peierls author the Frisch–Peierls memorandum, calculate that an atomic bomb might need as little as of enriched uranium to work. The memorandum is given to Mark Oliphant, who in turn hands it over to Sir Henry Tizard. April 10: MAUD Committee established by Tizard to investigate feasibility of an atomic bomb. May 21: George Kistiakowsky suggests using gaseous diffusion as a means of isotope separation. June 12: Roosevelt creates the National Defense Research Committee (NDRC) under Vannevar Bush, which absorbs the Uranium Committee. September 6: Bush tells Briggs that the NDRC will provide $40,000 for the uranium project. September – Belgian mining engineer Edgar Sengier orders that half of the uranium stock available from the Shinkolobwe mine in the Belgian Congo—about 1,050 tons—be secretly dispatched to New York by African Metals Corp., a commercial division of Union Minière.

January 19: Roosevelt formally authorizes the atomic bomb project. January 24: Compton decides to centralize plutonium work at the University of Chicago. June 19: S 1 Executive Committee is formed, consisting of Bush, Conant, Compton, Lawrence and Urey. June 25: S 1 Executive Committee selects Stone & Webster as primary contractor for construction at the Tennessee site. July–September: Physicist Robert Oppenheimer convenes a summer conference at the University of California, Berkeley to discuss the design of a fission bomb. Edward Teller brings up the possibility of a hydrogen bomb as a major point of discussion. July 30: Sir John Anderson urges Prime Minister Winston Churchill to pursue a joint project with the United States. August 13: The Manhattan Engineering District with James C. Marshall as District Engineer is established by the Chief of the United States Army Corps of Engineers, Major General Eugene Reybold, effective August 16. September 17: Major General Wilhelm D. Styer and Reybold order Colonel Leslie Groves to take over the project. September 23: Groves is promoted to brigadier general, and becomes director of the project. The Military Policy Committee, consisting of Bush (with Conant as his alternative), Styer and Rear Admiral William R. Purnell is created to oversee the project. September Lieutenant Colonel Kenneth Nichols meets Edgar Sengier in the New York offices of Union Minière. Nichols has been ordered by General Groves to find uranium. Sengier's answer has become history: "You can have the ore now. It is in New York, a thousand tons of it. I was waiting for your visit." Nichols reaches an agreement with Sengier that an average of 400 tons of uranium oxide will begin shipping to the US from Shinkolobwe each month. September 26: The Manhattan Project is given permission to use the highest wartime priority rating by the War Production Board. September 29: Under Secretary of War Robert P. Patterson authorizes the Corps of Engineers to acquire in Tennessee for Site X, which will become the Oak Ridge, Tennessee, laboratory and production site. October 100 tons of Sengier's uranium ore is sent to Canada for refining by Eldorado Mining and Refining in Port Hope, Ontario. October A special detachment from United States Army Corps of Engineers arrives in the Belgian Congo to reopen the Shinkolobwe mine in the Belgian Congo. Work involves draining water from flooded workings, upgrading the plant machinery and constructing transportation facilities. July 20: The Los Alamos organizational structure is completely changed to reflect the new priority. September 2: Two chemists are killed, and Arnold Kramish almost killed, after being sprayed with highly corrosive hydrofluoric acid while attempting to unclog a uranium enrichment device which is part of the pilot thermal diffusion plant at the Philadelphia Navy Yard. September 22: First RaLa test with a radioactive source performed at Los Alamos. September 26: The largest nuclear reactor, the B reactor, goes critical at the Hanford Site. Late November: Samuel Goudsmit, scientific head of the Alsos Mission, concludes, based on papers recovered in Strasbourg, that the Germans did not make substantial progress towards an atomic bomb or nuclear reactor, and that the programs were not even considered high priority. December 14: Definite evidence of achievable compression obtained in a RaLa test. December 17: 509th Composite Group formed under Colonel Paul W. Tibbets to deliver the bomb.

January: Brigadier General Thomas Farrell is named Groves' deputy. January 7: First RaLa test using exploding bridgewire detonators. January 20: First stages of K 25 are charged with uranium hexafluoride gas. February 2: First Hanford plutonium arrives at Los Alamos. April 22: Alsos Mission captures German experimental nuclear reactor at Haigerloch. April 27: First meeting of the Target Committee. May 7: Nazi Germany formally surrenders to Allied powers, marking the end of World War II in Europe; 100 ton test explosion at Alamogordo, New Mexico. May 10: Second meeting of the Target Committee, at Los Alamos. May 28: Third meeting which works to finalize the list of cities on which atomic bombs may be dropped: Kokura, Hiroshima, Niigata and Kyoto. May 30: Stimson drops Kyoto from the target list; it is replaced by Nagasaki. June 11: Metallurgical Laboratory scientists under James Franck issue the Franck Report arguing for a demonstration of the bomb before using it against civilian targets. July 16: the first nuclear explosion, the Trinity nuclear test of an implosion style plutonium based nuclear weapon known as the gadget at Alamogordo; Indianapolis sails for Tinian with Little Boy components on board. July 19: Oppenheimer recommends to Groves that gun type design be abandoned and the uranium 235 used to make composite cores (but Little Boy was not abandoned). July 24: President Harry S. Truman discloses to Soviet leader Joseph Stalin that the United States has atomic weapons. Stalin feigns little surprise; he already knows this through espionage. July 25: General Carl Spaatz is ordered to bomb one of the targets: Hiroshima, Kokura, Niigata or Nagasaki as soon as weather permitted, some time after August 3. July 26: Potsdam Declaration is issued, threatening Japan with "prompt and utter destruction". August 6: B 29 Enola Gay drops Little Boy, a gun type uranium 235 weapon, on the city of Hiroshima, the primary target. August 9: B 29 Bockscar drops a Fat Man implosion type plutonium weapon on the city of Nagasaki, the secondary target, as the primary, Kokura, is obscured by cloud and smoke. August 12: The Smyth Report is released to the public, giving the first technical history of the development of the first atomic bombs. August 13: Groves holds shipment of material for a third bomb, on his own authority as he could not reach Marshall or Stimson; as it would be a terrible mistake for us to send overseas the ingredients of another atomic bomb. A Fat Man bomb as enough U 235 for a second Little Boy bomb would not be available until December. August 14: Surrender of Japan to the Allied powers. August 21: Harry Daghlian, a physicist, receives a fatal dose (510 rems) of radiation from a criticality accident when he accidentally dropped a tungsten carbide brick onto a plutonium bomb core. He dies on September 15. September 4: Manhattan District orders shutdown of S 50 liquid thermal diffusion plant and the Y 12 Alpha plant. September 8: Manhattan Project survey group under Farrell arrives in Nagasaki. September 17: Survey group under Colonel Stafford L. Warren arrives in Nagasaki. September 22: Last Y 12 alpha track ceases operating. October 16: Oppenheimer resigns as director of Los Alamos, and is succeeded by Norris Bradbury the next day.

February: News of the Russian spy ring in Canada exposed by defector Igor Gouzenko is made public, creating a mild "atomic spy" hysteria, pushing American Congressional discussions about postwar atomic regulation in a more conservative direction. May 21: Physicist Louis Slotin receives a fatal dose of radiation (2100 rems) when the screwdriver he was using to keep two beryllium hemispheres apart slips. July 1: Able test at Bikini Atoll as part of Operation Crossroads. July 25: Underwater Baker test at Bikini. August 1: Truman signs the Atomic Energy Act of 1946 into law, ending almost a year of uncertainty about the control of atomic research in the postwar United States.

January 1: the Atomic Energy Act of 1946 (known as the McMahon Act) takes effect, and the Manhattan Project is officially turned over to the United States Atomic Energy Commission. August 15: Manhattan District is abolished.