Enewetak Atoll Nuclear Tests: "Blast Measurment in Operation Sandstone" 1948 US Air Force

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Originally a public domain film from the National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.

The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

https://en.wikipedia.org/wiki/Operation_Sandstone

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

Operation Sandstone was a series of nuclear weapon tests in 1948. It was the third series of American tests, following Trinity in 1945 and Crossroads in 1946, and preceding Ranger. Like the Crossroads tests, the Sandstone tests were carried out at the Pacific Proving Grounds, although at Enewetak Atoll rather than Bikini Atoll. They differed from Crossroads in that they were conducted by the Atomic Energy Commission, with the armed forces having only a supporting role. The purpose of the Sandstone tests was also different: they were primarily tests of new bomb designs rather than of the effects of nuclear weapons. Three tests were carried out in April and May 1948 by Joint Task Force 7, with a work force of 10,366 personnel, of whom 9,890 were military.

The successful testing of the new cores in the Operation Sandstone tests rendered every component of the old weapons obsolete. Even before the third test had been carried out, production of the old cores was halted, and all effort concentrated on the new Mark 4 nuclear bomb, which would become the first mass-produced nuclear weapon. More efficient use of fissionable material as a result of Operation Sandstone would increase the U.S. nuclear stockpile from 56 bombs in June 1948 to 169 in June 1949...

The objectives of the Sandstone series of tests were to:

- test nuclear cores and initiators;

- improve the theory and knowledge of implosion 

- type weapons;

- test levitated cores;

- test composite cores; and

- determine the most economic designs in terms of efficient use of fissionable material.

Levitation meant that instead of being immediately inside the tamper, there would be an air gap between the tamper and the core, which would be suspended inside on wires. This would allow the tamper to gain more momentum before striking the core... the wires had to be strong enough to withstand being dropped from an aircraft, but thin enough to not disturb the spherical symmetry of the implosion. The Theoretical Division at Los Alamos, known as T Division, had run computer calculations on the levitated core as early March 1945. The use of the levitated core had been proposed during the planning for Operation Crossroads, but it had been decided instead to use the existing solid core... For Sandstone, however, it was decided that at least two of the three tests would use levitated cores.

The motivation behind the composite core was to make better use of the available fissionable material. The use of uranium-235 in an implosion weapon instead of the inefficient gun type Little Boy was an obvious development. However, while plutonium was more expensive and harder to produce than uranium-235, it fissions faster, because it makes better use of the neutrons its fission produces. On the other hand, the slower reaction of uranium-235 permits the assembly of super-critical masses, making it theoretically possible to produce weapons with high yields. By July 1945, Oppenheimer and Groves were considering using both materials in a composite core containing 3.25 kilograms (7.2 lb) of plutonium and 6.5 kilograms (14 lb) of uranium-235. The composite cores became available in 1946. Los Alamos' priority then became the development of an all-uranium-235 core. By January 1948 the national stockpile contained 50 cores, of which 36 were composite Christy cores, nine were plutonium Christy cores, and five were composite levitated cores. Testing the new levitated, composite and uranium-235 cores would require at least three test firings.

More efficient weapons would require less efficient initiators. This meant that less polonium would be required. At the time of Sandstone, the national stockpile of polonium-beryllium initiators consisted of 50 A-Class initiators, with more than 25 curies of polonium, and 13 B-Class initiators with 12 to 25 curies. During Sandstone, at least one test would be conducted with a B-Class initiator...

The Mark III bombs were withdrawn from service in 1950. At the same time, new production plants were coming online and the Wigner effect problem had been solved. By May 1951, plutonium production was twelve times that of 1947, while uranium-235 production had increased eight-fold...