John von Neumann
John von Neumann, also known as Neumann János Lajos, is an Hungarian scientist, mathematician, physicist, and computer scientist. He is seen as the father of many disciples such as: game theory, quantum mechanics, and operator theory. He was also a major contributor to hydrodynamics, statistics, the digital computers, and so many more topics.1 One of his greatest contributions is towards the Manhattan project. He helped design a crucial piece for the atom bomb that was used in World War Two and helped decided where the bomb would be used.
Neumann had a lot of interests in explosions. This led him to be a leading expert and contributor to knowledge in hydrodynamics and shock waves. Because of his knowledge and research in these fields, he was acquired by American militaries for consultancies, like the Navy. His involvement with the Navy led him to start working on the Manhattan Project.2 Neumann was a consultant to the Manhattan Project in Los Alamos, however he was able to solve a big problem the team was having with the atomic bomb.
In 1943, two bombs were being built: Little Man and Fat Man. Neumann worked primarily on Fat Man. Fat man was different compared to Little Man. Little Man used Uranium-235, however since this is very rare material and purifying uranium was not successful, Fat Man used Plutonium-239. Because Little Man used Uranium-235, it used a detonation involving uranium being shot at another piece of uranium to set off a fission chain reaction, which would detonate the bomb eventually. This did not work for plutonium-239 used in Fat Man.3 This is because there was some amounts of isotope-plutonium-240, which had a high rate of spontaneous fission. Even before the gun could shoot plutonium at plutonium, a small detonation would have already begun because of the traces of plutonium-240. This meant the bomb would fail to blow up.
Neumann had the exact solution to the problem: implosion. The implosion method basically involved having explosions occur all around the plutonium in order consolidate it. This allowed the plutonium to reach critical mass and begin fission which would ultimately lead to an explosion. This method was not made by Neumann, however he had perfected the method in a lab he supervised in Aberdeen Proving Grounds in Maryland. This method was quickly adopted by the Manhattan Project team because the plutonium would prevent detonation before assembly (unlike in the gun detonation) and that the implosion would increase the efficiency of the weapon.4
Even with implosion being chosen as the detonation method, it was still difficult to get a uniform explosion around the plutonium. Neumann once again stepped in and designed the explosive lens that would surround the Fat Man. His design used high explosives in shaped charges to implode a sphere.5 The explosive lens would send shockwaves all over the plutonium core making it compressed and denser, and also assured that fission would begin at the right time.
In 1945, the prototype for the Fat Man was made. It was going to be tested in Trinity, New Mexico. Neumann and other scientists working on the project bore witness to the destruction wreaked by the bomb. Its power was devastating, over 21,000 tons of TNT. 6 Neumann’s Fat Man was ready for World War II. Neumann was apart of a council that chose what got to be bombed. Neumann had chosen Kyoto, but that was denied by the Secretary of War. It was eventually decided that Hiroshima and Nagasaki would receive the bombs and Neumann made calculations regarding optimal detonation height for maximum destruction, death toll, etc.7
While Neumann was just a consultant for for the Manhattan Project, he played a major role in the production of Fat Man. It was due to his suggestion and his design that the Fat Man was much more efficient and more powerful compared to Little Man.
Bibliography
1Poundstone, William. “John von Neumann.” Encyclopædia Britannica. October 15, 2017. Accessed December 26, 2017. https://www.britannica.com/biography/John-von-Neumann.
2John von Neumann.” John von Neumann – Engineering and Technology History Wiki. Accessed December 26, 2017. http://ethw.org/John_von_Neumann.
3“Science Behind the Atom Bomb.” Atomic Heritage Foundation. June 05, 2014. Accessed December 26, 2017. https://www.atomicheritage.org/history/science-behind-atom-bomb.
4John Von Neumann & The Atomic Bomb. Directed by David, Hoffamn. Youtube. September 17, 2013. Accessed December 26, 2017. John Von Neumann & The Atomic Bomb.
5Flank, Lenny. “Fat Man and Little Boy: The Design of the Atomic Bombs.” Hidden History. September 17, 2014. Accessed December 26, 2017. https://lflank.wordpress.com/2015/01/14/fat-man-and-little-boy-the-design-of-the-atomic-bombs/.
6 History.com Staff. “The Trinity Test.” History.com. 2010. Accessed December 26, 2017. http://www.history.com/topics/world-war-ii/trinity-test.
7Macrae, Norman. John von Neumann the scientific genius who pioneered the modern computer, game theory, nuclear deterrence, and much more. Place of publication unknown: American Mathematical Society, 2014.
Written by Kameron Gill