The following is a timeline of the Manhattan Project, the effort by the United States, United Kingdom, and Canada to develop the first nuclear weapons for use during World War II. The following includes a number of events prior to the official formation of the Manhattan Project as the Manhattan Engineering District (MED) in August 1942 and a number of events after the atomic bombings of Hiroshima and Nagasaki, until the MED was formally replaced by the United States Atomic Energy Commission in 1947.
The first page of the
MAUD Committee report, 15 July 1941, written by James Chadwick.
- February 26: Conclusive discovery of plutonium by Glenn Seaborg and Arthur Wahl.
- April - May: MAUD committee research in Liverpool, led by Chadwick, showed that a bomb's critical mass could be reached with maybe less than 8 kg of uranium. Nazis' bombing of the immediate environs of his lab, plus the burden of keeping such key findings secret from all others there, made Chadwick desolate: "it was inevitable.... Some country would put them into action.... I had to then take sleeping pills. It was the only remedy."
- May 17: A report by Arthur Compton and the National Academy of Sciences is issued which finds favorable the prospects of developing nuclear power production for military use. Vannevar Bush creates the Office of Scientific Research and Development (OSRD)
- July 2: The MAUD Committee chooses James Chadwick to write the second (and final) draft of its report on the design and costs of developing a bomb.
- July 15: The MAUD Committee issues final detailed technical report on design and costs to develop a bomb. Advance copy sent to Vannevar Bush who decides to wait for official version before taking any action.
- August: Mark Oliphant travels to USA to urge development of a bomb rather than power production [1]
- October 3: Official copy of MAUD Report (written by Chadwick) reaches Bush.
- October 9: Bush takes MAUD Report to Roosevelt, who approves Project to confirm MAUD's findings: "Roosevelt indicated that he could find a way to finance the project and asked Bush to draft a letter so that the British government could be approached 'at the top.' " [2]
- December 6: Vannevar Bush holds a meeting to organize an accelerated research project, still managed by Arthur Compton. Harold Urey is assigned to develop research into gaseous diffusion as a uranium enrichment method, while Ernest O. Lawrence is assigned to investigate electromagnetic separation methods.
- December 7: The Japanese attack Pearl Harbor. The United States issues a formal declaration of war against Japan the next day. Four days later, Nazi Germany declares war on the United States.
- December 18: First meeting of the OSRD sponsored S-1 project, dedicated to developing fission weapons
Massive
calutrons at Oak Ridge, Tennessee, worked around the clock to enrich uranium for a bomb.
The two types of fission weapon designs pursued during the Manhattan Project.
- April 5: At Los Alamos, Emilio Segrè receives the first sample of reactor-bred plutonium from Oak Ridge, and within ten days discovers that the spontaneous fission rate is too high for use in a gun-type fission weapon.
- May: Fermi at Los Alamos tests the world's third reactor, LOPO, the first aqueous homogeneous reactor, and the first fueled by enriched uranium.
- July 4: Oppenheimer reveals Segrè's final measurements to the Los Alamos staff, and the development of the gun-type plutonium weapon "Thin Man" is abandoned. Designing a workable "implosion" design becomes top priority of the laboratory.
- July 20: The Los Alamos organizational structure is completely changed to reflect the new priority of "implosion".
- July 25: First preliminary test of the RaLa Experiment series performed
- September 2: chemists Peter N. Bragg, Jr. [3] and Douglas P. Meigs [4] are killed, and Arnold Kramish almost killed, while attempting to unclog a uranium enrichment device which is part of the pilot thermal diffusion plant at the Philadelphia Navy Yard. Two soldiers, George LeFevre and John Tompkins, also receive extensive injuries. An explosion of liquid uranium hexafluoride burst nearby steam pipes, and steam combined with the uranium hexafluoride to spray them with highly corrosive hydrofluoric acid. See also [5] [6] and [7]
- September 22: First RaLa test with a radioactive source performed
- December 9: 509th Composite Group of USAAF constituted to deliver the bomb
- December 14: Definite evidence of achievable compression obtained in a RaLa test
- Mid-December: Successful test of explosive lens for Fat Man.
- January: Gen. Thomas Farrell named Gen. Groves' deputy.
- January 7: First RaLa test using exploding bridgewire detonators
- January 14: Second RaLa test using exploding bridgewire detonators
- May 7: Nazi Germany formally surrenders to Allied powers, marking the end of World War II in Europe.
- May 10–11: second meeting of the Target Committee, at Los Alamos, which works to finalize the list of cities on which atomic bombs may be dropped.[8]
- 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" test of an implosion-style plutonium-based nuclear weapon known as "the gadget", near Alamogordo, New Mexico.
- 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.[9] [10]
- August 6: "Little Boy", a gun-type uranium-235 weapon, is used against the city of Hiroshima, Japan (the primary target).
- August 9: "Fat Man", an implosion-type plutonium-239 weapon, is used against the city of Nagasaki, Japan (the secondary target, as the primary target, Kokura, was obscured by cloud).
- August 12: The Smyth Report is released to the public, giving the first technical history of the development of the first atomic bombs.
- August 15: Surrender of Japan to the Allied powers.
- August 21: Harry K. Daghlian, Jr., 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.
- October 16: Oppenheimer resigns as director of Los Alamos, and is succeeded by Norris Bradbury the next day.
- February: News of the Canadian spy ring exposed by defector Igor Gouzenko is made public (leaked by General Groves), creating a mild "atom spy" hysteria, pushing American Congressional discussions about postwar atomic regulation in a more conservative direction.[1]
- May 21: Louis Slotin, a physicist, received a fatal dose of radiation (2100 rems) when the screwdriver he was using to keep two beryllium hemispheres apart slipped; they were placed around the same plutonium core that had irradiated Daghilan. The upper hemisphere fell, causing a "prompt critical" reaction with a burst of hard radiation. Slotin lifted the upper hemisphere with his left hand and dropped it on the floor, so preventing a more serious accident. He was rushed to hospital, and died nine days later on May 30. Slotin had spent many hours with the dying Daghlian in 1945.
- August 1: Harry S. 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.
[edit] References
- ^ Gregg Herken, The Winning Weapon: The Atomic Bomb in the Cold War, 1945-1950. New York: Knopf, 1980, pp. 133.
[edit] External links
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