Lead: With the first sustained nuclear reaction in December, 1942, the Roosevelt Administration decided to harvest the energy of the atom by creating a weapon so powerful that it might possibly bring an end to World War II.

Tag: A Moment in Time with Dan Roberts.

Content: The executive director of the Manhattan Engineer District, the project to build the bomb, was Brigadier General Leslie Groves. He in turn chose J. Robert Oppenheimer, professor of physics at the University of California at Berkeley, who assembled the team that solved the theoretical and scientific problems associated with the bomb. Groves also selected a naval ordinance officer, Captain William S. "Deak" Parsons to tackle the construction and delivery of the weapon.

First conceived by Hungarian physicist Leo Szilard, the atomic bomb, if it were to be more than just a very expensive dud, had to bring together a mass of uranium large enough to achieve a sustained reaction and quick enough for it to reach critical mass, that point at which enriched uranium - 235 blows up with terrifying force. To reach this goal Parsons and Oppenheimer took two paths. The first concentrated on a bomb that would use the very small amount of uranium-235 that could be purified given the technology of the early 1940s. They devised a bomb that consisted basically of a gun inside the bomb casing that would fire one shaped charge of uranium into another, achieve critical mass, and blow up. Eventually, the bomb that was dropped on Hiroshima, named Little Boy, used this glorified gun technology.

The second path chose plutonium, a refined form of uranium, which was relatively more plentiful but unfortunately would not respond to the gun method of achieving critical mass. Because of the make-up of plutonium, the gun could not get enough of it together quick enough to do much more than blow up a house, certainly not a city. The solution was an implosion bomb. Instead of a long gun, the plutonium bomb, named Fat Boy, was round with explosive charges shaped around a plutonium core about the size of a grape fruit. When the charges went off they compressed the plutonium into critical mass and it went off. The first atomic bomb test in New Mexico on July 16, 1945 was of this variety, as was the second bomb dropped on Nagasaki a month later.

The Manhattan Project was one of the great intellectual and technical achievements of the twentieth century. It cost a billion dollars, involved thousands of man hours, but in the end achieved its purpose: the end of World War II.

At the University of Richmond, this is Dan Roberts.

Resources

Christman, Al. "The Atom Bomb: Making it Happen," American Heritage of Invention and Technology 11 (1, Summer, 1995), 22-35.

Cooper, Dan. "The Atom Bomb: Making it Possible, "American Heritage of Invention and Technology 11 (1, Summer, 1995), 10-21.

Genion, William, editor. The Affects of the Atomic Bombs on Hiroshima and Nagasaki by the United States Strategic Bombing Survey. Santa Fe: Genion Publishing, 1973.

Groves, Leslie R. Now It Can be Told. New York: Harper & Row Publishers, 1962.

Maddox, Robert James, " The Biggest Decision: Why We Had to Drop the Atomic Bomb," American Heritage 46 (3, May/June, 1995), 70-77.

Stehling, Kurt R. "World Shaking Week in December: When the Work in Quiet Lab in Berlin and a Walk in the Snow in Sweden Opened Up the Pandora's Box of Fission," Smithsonian 4 (9, December, 1973), 88-89.

Wyden, Peter. Day One: Before Hiroshima and After. New York: Simon and Schuster Publishing Company, 1984.

Copyright 1995 by Educational Broadcast, Inc.