The Manhattan Project - Personalities and Problems Fromm Institute - PDF document

11/5/20 The Manhattan Project - Personalities and Problems Fromm Institute Fall 2020 bebo.white@gmail.com Lecture 7 submitted questions/comments from lecture 6 1. Why do you have a clock stopped at 10:45 and 30? 2. Could you re-explain implosion design? (**) 3. I have a riddle that Feynman might have given to his colleagues: How did I devise the lock combo 42-52-60? [First answer gets a prize from Bebo] 4. Is it true that after Germany surrendered, Nazi scientists were brought to the US to assist the Manhattan Project? (Farm Hall, Lecture 8) 5. How did scientists figure out that plutonium would pre-detonate? 6. Had German targets been selected? (**) 7. Were there Nazi spies? 8. Did they return the silver to the US Treasury? 9. What was the ratio of women to men working at Oak Ridge? 1

11/5/20 remember the 3 preliminary designs from the serber lectures? “the gadget”/“the device” - why testing was necessary •Pu(239) only 40% sphere critical mass, more stable •U(238) damper reflects neutrons •implosion squeezes Pu(239) sphere to critical density •charges must be uniform and timed perfectly 2

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11/5/20 remember the two sub-projects? • Project Alberta/Project A (readying bombs for delivery and use) - lead by “Deak” Parsons - some activities had begun in June 1943 • Project Trinity (bomb testing) - lead by Kenneth Bainbridge- work had begun Spring, 1944 project trinity • Objectives: • Characterize the physics of the implosion not possible with experiments in the laboratory • Analyze the symmetry of the implosion created by the explosive lenses • Determine if the energy release is comparable with that contemplated for final use • Assess the resulting damage 4

11/5/20 test site criteria (1944) 1. Flat 2. Good climate 3. Distant ranches and settlements 4. Minimal travel time for staff and equipment 5. Security (especially disassociation with Los Alamos) 8 possible test sites were considered (1944) • Tularosa Basin, southern New Mexico (location of White Sands Missile Range) • Jornada del Muerto (Journey of Death), northwest corner of Alamogordo Bombing Range (*) • Desert training area near Rice, California, southern tip of Mojave Desert (*) • San Nicolas Island off the coast of Southern California • Lava region south of Grants, New Mexico • Cuba, New Mexico • Sand bars off Padre Island, Texas • San Luis Valley region near the Great Sand Dunes National Monument in Colorado 5

11/5/20 Jumbo (800 yds) McDonald Ranch House (2 miles) Base Camp (10 miles) • Decision on September 7, 1944 • Setup team started on December 30, 1944 • Jumbo arrived in June 1945 Since it was unofficial and in an active test zone, it did get accidentally practice bombed! may 7 - test rehearsal • Dry run for assignments and services • 100 tons of high explosives combined with a very small amount of radioactive materials • Blast from a 20-foot platform 6

11/5/20 the world’s first “dirty bomb” 7

11/5/20 March 10, 1944 Brig. Gen. L. R. Groves P. 0. Box2610 Washington, D. C. Dear General Groves: ... [In regard to] a containing sphere [Jumbo] for proof tiring, there were a number of points made which I should like to have down in the record. . . . ... It was not known to us whether it could be made in the form of a single sphere or would have to be built up from plates. Excluding the extra weight introduced by manholes and reinforcements, the weight of the sphere was given by us as 80 tons provided steel could be obtained of yield strength 60,000 psi or better. You expressed the conviction that individual castings in excess of a hundred tons would introduce very serious transportation problems which should be avoided if possible.... We shall attempt to have a container fabricated and completely assembled by September so that it may play as useful a part as possible in the later stages of implosion development. [J. Robert Oppenheimer] the story of jumbo • Since Pu(239) was in short supply, it was proposed to contain the blast to allow recovery if the test was unsuccessful • Steel cylinder - 10 ft. in diameter, 25 feet long, 14 inch walls, 240 tons • At the time the heaviest item ever shipped by rail from Barberton, Ohio; left early April, arrived early June on a 64-wheel trailer • Use was re-thought after concern that it would limit data collection 8

11/5/20 July 11, 1945 Comdr. N. E. Bradbury K. Bainbridge Jumbo, Jumbo is a silent partner in l.OiAl1a11pplas&iand;Jti11.aoldkasJ,yet,.. K. Bainbridge planning for the test • As per the President’s Interim Committee meeting on May 31, no foreign delegations would be invited • The original July 4 date was postponed but a hard date was set for July 16 to coincide with the Potsdam Conference between Truman, Churchill, and Stalin • Note : the test was scheduled for the same day that the Indianapolis left for Tinian 9