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Transcript of 60 years of the Atomic Bomb - christie Sharing/A-BOMB presentation.pdfآ  The atomic bomb (A-bomb)...

  • 1

    60 years of the Atomic Bomb

    August 6, 1945

    Presented By: Amila Perera

    The Manhattan Project • In 1939, the Nazis were rumored to be developing an atomic bomb. • In August 1942, the Manhattan Engineer District was created by the

    US government to meet the goal of producing an atomic weapon under the pressure of ongoing global war. Its central mission became known as the Manhattan Project.

    • secret atomic energy communities were created overnight. The weapon itself would be built at the Los Alamos laboratory, under the direction of physicist J. Robert Oppenheimer.

    • America needed to build an atomic weapon before Germany or Japan did. This was a top-secret project.

    • General Leslie R. Groves was appointed to direct this top-secret project.

    • Italian physicist Enrico Fermi managed the University of Chicago reactor, called Chicago Pile 1 (CP-1). Nobel Prize-winner Fermi had fled Fascist Europe.

    • On the afternoon of December 2, 1942, the first controlled nuclear reaction occurred. Humankind had controlled energy released from the nucleus of the atom.

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    The People General Leslie Groves was the military leader of the Manhattan project. He named it after the Manhattan district where it originated.

    The German efforts to develop nuclear weapons, led by Werner Heisenberg, was one of the main motivations for the Manhattan Project.

    Albert Einstein’s letter helped convince President Roosevelt to begin the Manhattan Project. His energy-mass relation (E=mc2) was one of the cornerstones for nuclear physics.

    Leo Szilard He sought the help of eminent physicist Albert A Roosevelt that motivated the project’s inception.

    The People

    Enrico Fermi On December 2, 1942, he, along with Szilard, produced a controllable chain reaction which was the foundation of the atomic bomb.

    From left: Neils Bohr, Oppenheimer, Feyman and Fermi

    Glen Seaborg Discoverer of the isotope Plutonium-238 (P-238). Seaborg also developed a process for separating weapons-grade plutonium from uranium in nuclear reactors.

    Neils Bohr Bohr was involved directly in the Manhattan Project, acting as a consultant and visiting Los Alamos on a regular basis. He discovered that the rare isotope Uranium-235 (U-235) was fissionable. This allowed for neutrons to be released from the tiny fragments produced in fission.

    Richard Feyman Teaming up with Hans Bethe, he figured out the key mathematical equations, such as the critical masses.

    Robert Oppenheimer In 1943, Oppenheimer became the scientific director for the Manhattan Project.

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    The Equation

    Albert Einstein’s letter helped convince President Roosevelt to begin the Manhattan Project. His energy-mass equation (E=mc2) was one of the cornerstones for nuclear physics.

    "Politics are for the moment. Equations are for eternity."

    The Letter

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    Without Warning

    A position paper by some of the scientists involved in developing the atomic bomb opposing use of the bomb without and requesting a demonstration use. The paper was submitted to the Interim Committee, but the committee reconfirmed its decision to bomb without warning.

    Nuclear Fusion Nuclear fusion -Two smaller atoms are brought, usually hydrogen or hydrogen isotopes (deuterium, tritium), together to form a larger one (helium or helium isotopes); this is how the sun produces energy.



  • 5

    The Example



    The best example for Nuclear fusion is the nuclear reaction happening in the sun.

    Nuclear Fission •Nuclear fission - You can split the nucleus of an atom into two smaller fragments with a neutron. This method usually involves isotopes of uranium (uranium-235, uranium-233) or plutonium-239.

    Hiroshima Atomic Bomb 10-20 kg of U235 ~ 1 kg achieved fission ~ 15,000 tons of TNT in explosion Total bomb weight ~ 4000 kg



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    The Basic Principle of the Atomic Bomb

    The splitting of atomic nuclei releases enormous energy. When a single free neutron strikes the nucleus of an atom of fissile (radioactive) material like uranium 235 or plutonium 239, it usually knocks two or three more neutrons free. Energy is released when those neutrons split off from the nucleus, and the newly released neutrons strike other uranium 235 (or plutonium 239) nuclei, splitting them in the same way, releasing more energy and more neutrons. This chain reaction spreads almost instantaneously. The atomic bomb (A-bomb) was a weapon of destruction that used the power released by the splitting of atomic nuclei.

    The Timeline • Uranium Fission

    1938 Otto Hahan and Fritz Strassmann's discovery of fission steered Germany toward developing an atomic weapon. This motivated the U.S. to launch the Manhattan Project.

    • The Race for the Atomic Bomb Begins 1939-1941 World War II started September 1, 1939, when Germany attacked Poland. By 1941, the Germans were leading the race for the atomic bomb. They had a heavy-water plant, high-grade uranium compounds, a nearly complete cyclotron, capable scientists and engineers, and the greatest chemical engineering industry in the world.

    • The Research Effort Struggles 1941-1945 Factors including internal struggles, a major scientific error, and the devastation of total war compromised any successful research toward a German atom bomb. Unlike the American program, the Germans never had a clear mission under continuously unified leadership.

    • The First Controlled Nuclear Reaction 1942 At the University of Chicago reactor, Enrico Fermi oversaw the first controlled energy release from the nucleus of the atom.

    • U-235 Output Begins 1945 After intense effort, the Y-12 plant in Oak Ridge, Tenn., began to produce bomb-grade U-235, which was shipped to Los Alamos, N.M. U-235 was used in the Little Boy bomb and plutonium was used in the Fat Man bomb produced at Los Alamos.

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    Workers with the Manhattan Engineer District gently carry the plutonium core for the world's first atomic bomb—in the form of two small hemispheres—into the McDonald Ranch house (near the Trinity test site) for assembly, July 12, 1945

    The Prototype

    Physicist Norris Bradbury and Boyce McDaniel (part of the Manhattan Project's Special Engineering Detachment) stand at the top of a 100 foot (30.5 meter) tower after helping to assemble the world's first atomic bomb on July 15, 1945, one day before the Trinity test. Detonators and cables cover the surface of the handmade device, nicknamed the "Gadget." The "Gadget" was detonated at 05:29:45 mountain war time on July 16, 1945 at the Trinity site (now part of the White Sands Missile Range, New Mexico). The device had a yield of 23 kilotons ± 3 kilotons.

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    Cost of the Project

    • US$ 1.9 billion (now more than US$ 21.6 billion)

    The Bomber

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    The Crew

    August 5, 1945 • They loaded the bomb into the Enola Gay that afternoon. "Little Boy" was

    12 feet long and 28 inches in diameter - bigger than any bomb Tibbetts had ever seen. Its explosive power equalled 20,000 tons of TNT; or roughly as much as two thousand Superfortresses could carry - all in a single bomb that weighed about 9,000 pounds. Deak Parsons practiced the delicate arming process. That night the crew was briefed, for the first time, on the nature of their weapon - an atomic bomb.

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    August 6, 1945 • They started engines at 2:30 AM on the morning of August 6, 1945.

    Three hours after takeoff, they flew over Iwo Jima at dawn, where 5,500 Americans and 25,000 Japanese had died, so that the USAAF could use Iwo as an emergency landing field. They adjusted course and headed northwest. At 7:30, Deak Parsons completed his adjustments; the atomic bomb was live. They climbed slowly to their bombing altitude of 30,700 feet.

    • They looked down at the city below. The other crewmen verified that it was indeed Hiroshima. They spotted the Initial Point, or I.P. They turned and headed almost due west. Tom Ferebee peered into his Norden bombsight, and cranked in the information to correct for the south wind. Tibbets reminded the crew to put on their heavy dark Polaroid goggles, to shield their eyes from the blinding blast. It had been calculated to have the intensity of ten suns. They easily spotted the distinctive T-shaped bridge that was their primary. 90 seconds before drop, he turned the controls over to Tom Ferebee, the bombardier.

    The Time At 8:15 (Hiroshima time), they dropped "Little Boy" and made a 155 degree diving turn to the right. Unable to fly the plane with the dark goggles, they shoved them aside. 43 seconds later, a tingling in Tibbets' teeth told him of the Hiroshima explosion: the bomb's radioactive forces interacting with his fillings. The bomb exploded at 1890 feet above the ground. Bob Caron, the tail gunner was the only crew member to see the fireball. Even wearing the goggles, he thought he was blinded. The plane raced away, while the shockwave from the explosion raced toward them at 1,100 feet per second. When the shockwave hit, it felt like a near-miss from flak. The mushroom cloud boiled up, 45,000 feet high, three miles above them, and it was still rising. They flew away, shocked and horrified at the sight below. The city had completely disappeared under a blanket of smoke and fire. They