The Manhattan Project
Was centered in Los Alamos, New Mexico
I just got back into the country and still haven’t seen the Oppenheimer movie. Maybe I should wait until I have written all of the posts about Oppenheimer in New Mexico before I do.
In this post, I have briefly outlined the Manhattan Project and the development of the atomic bomb. I’ve included basic information about nuclear reactions and how they work in the creation of a nuclear bomb. You can’t really talk about Oppenheimer and Los Alamos without first talking about the bombs themselves.
The Manhattan Project
The first atomic bomb was built in Los Alamos, New Mexico, during World War II under a program called the Manhattan Project. The project was code named Manhattan after the site of Columbia University where much of the early research was developed.
President Franklin Roosevelt was motivated to pursue nuclear weapon research after he received a letter from Nobel Prize laureate Albert Einstein in October 1939 that warned that Nazi Germany was likely already at work on developing a nuclear weapon.
Los Alamos was approved as the site for the main atomic bomb scientific laboratory on November 25, 1942, and was given the code name Project Y. General Leslie Groves was the U.S. Army General in charge of the Manhattan Project during World War II. Robert Oppenheimer was its first director, serving in that role from 1943 to December 1945.
The Bombs Produced
Scientists at Los Alamos developed two distinct types of atomic bombs by 1945—a uranium-based design called “Little Boy” and a plutonium-based weapon called “Fat Man.”
How these bombs got such names is due to their shape and from characters in literature. The one that hit Hiroshima was originally called “Thin Man” because it was a long, thin device and the name came from the Thin Man detective novels written by Dashiell Hammett. “Little Boy” was a modified version of Thin Man. The difference between the two was the materials used: Little Boy used uranium isotopes and Thin Man used plutonium. The “Fat Man” was round and fat, so it was named after a character in Dashiell Hammett’s 1930 novel The Maltese Falcon.
Atomic Bombs get their Energy from Nuclear Fission
In nuclear fission, the nucleus of an atom of radioactive material splits into two or more smaller nuclei, which causes a sudden, powerful release of energy. This is done by a neutron striking the nucleus of the radioactive isotopes uranium-235 or plutonium-239. Isotopes of a particular element are only different in the number of neutrons in the nucleus (some isotopes are more stable and don’t easily undergo fission). The isotope is indicated by the number of neutrons it has in the nucleus and is included after the element’s name.
During fission, as the nucleus splits, extra neutrons escape and can strike other nuclei, which then emit more neutrons that split still more nuclei. This series of rapidly multiplying fissions creates a chain reaction in which nearly all the fissionable material is consumed, in the process generating the explosion of an atomic bomb.
For a chain reaction to happen, there must be a minimum amount of fissionable material to generate enough neutrons to keep the reaction going. This is called “critical mass”. To detonate a bomb, an assembly of fissionable material must be brought from a subcritical to critical mass quickly. There were two methods used to achieve this. One is to bring two subcritical masses together, at which point their combined mass becomes a critical one. A second method is that of implosion in which a core of fissionable material is instantly compressed into a smaller size increasing the density. Because it is denser, the nuclei are more tightly packed and the chances of an emitted neutron’s striking a nucleus are increased.
Other Manhattan Project Locations
Two other primary locations besides Los Alamos made up the Project: Hanford, Washington (Site W) and Oak Ridge, Tennessee (Site X). Both of these locations were in remote locations to help with the secrecy of the project. These sites were responsible for providing the fuel for the bombs.
Hanford, Washington – Site W
The Hanford site was established in 1943 and was home to the first full-scale plutonium production reactor in the world. Plutonium is a synthetic element (not found in the world naturally) that had, at that time, only been isolated in the laboratory (it had only been discovered in February 1941). Since the scientists wanted to use plutonium to fuel the Fat Man bomb, it had to be manufactured in a large enough quantity. The plutonium manufactured at the site was successfully used in the first atomic bomb, which was tested at the Trinity Nuclear Test in New Mexico (subject of my next post), and in the Fat Man bomb used in the bombing of Nagasaki.
Oak Ridge, Tennessee – Site X
Site X at Oak Ridge, Tennessee was built for the purpose of enriching uranium for the first atomic bombs. It began operating in November 1943, separating uranium-235 (the enriched uranium) from natural uranium which is 99.3% uranium-238. Therefore, a large amount of natural uranium was needed to be processed to yield the desired isotope. The Uranium-235 was used for the Little Boy nuclear weapon that was dropped on Hiroshima, Japan on August 6, 1945.
Next Time
My next post will be about the Trinity Test Site near Alamogordo, New Mexico. It was where the first atomic bomb from the Manhattan Project was detonated. There are two times a year that the military open the site for the public to visit. I suspect it will be very crowded this October because of the movie Oppenheimer.
Please like this post as it helps the post to be seen. In addition, please subscribe if you aren’t already subscribed and share with a friend!!
