The Manhattan Project

On the morning of August 6, 1945, a B-29 bomber named Enola Gay flew over the industrial city of Hiroshima, Japan and dropped the first atomic bomb ever. The city went up in flames caused by the immense power equal to about 20,000 tons of TNT. The project was a success. They were an unprecedented assemblage of civilian, and military scientific brain power-brilliant, intense, and young, the people that helped develop the bomb. Unknowingly they came to an isolated mountain setting, known as Los Alamos, New Mexico, to design and build the bomb that would end World War 2, but begin serious controversies concerning its sheer power and destruction. I became interested in this topic because of my interest in science and history. It seemed an appropriate topic because I am presently studying World War 2 in my Social Studies Class. The Hiroshima and Nagasaki bombings were always taught to me with some opinion, and I always wanted to know the bomb itself and the unbiased effects that it had. This I-search was a great opportunity for me to actually fulfill my interest.

The Manhattan Project was the code name for the US effort during World War II to produce the atomic bomb. It was appropriately named for the Manhattan Engineer District of the US Army Corps of Engineers, because much of the early research was done in New York City (Badash 238). Sparked by refugee physicists in the United States, the program was slowly organized after nuclear fission was discovered by German scientists in 1938, and many US scientists expressed the fear that Hitler would attempt to build a fission bomb. Frustrated with the idea that Germany might produce an atomic bomb first, Leo Szilard and other scientists asked Albert Einstein, a famous scientist during that time, to use his influence and write a letter to president FDR, pleading for support to further research the power of nuclear fission (Badash 237). His letters were a success, and President Roosevelt established the Manhattan Project.

Physicists from 1939 onward conducted much research to find answers to such questions as how many neutrons were emitted in each fission, which elements would not capture the neutrons but would moderate or reduce their velocity , and whether only the lighter and scarcer isotope of uranium (U-235) fissioned or the common isotope (U-238) could be used. They learned that each fission releases a few neutrons. A chain reaction, therefore, was theoretically possible, if not too many neutrons escaped from the mass or were captured by impurities. To create this chain reaction and turn it into a usable weapon was the ultimate goal of the Manhattan Project.

In 1942 General Leslie Groves was chosen to lead the project, and he immediately purchased a site at Oak Ridge, Tenn., for facilities to separate the necessary uranium-235 from the much more common uranium-238. Uranium 235 was an optimal choice for the bomb because of its unusually unstable composition. Thus, the race to separate the two began. During that time, the work to perfect the firing mechanism and structure of the bomb was also swiftly underway.

General Groves' initial task had been to select a scientific director for the bomb project. His first two choices, Ernest O. Lawrence, director of the electromagnetic separation project, and Arthur H. Compton, director of Chicago Metallurgical Laboratory, were not available. Groves had some doubts regarding the next best candidate, J. Robert Oppenheimer (Wood 2). Finally, Groves gambled on Oppenheimer, a theoretical mathematician, as director of the weapons laboratory, built on an isolated mesa (flat land area) at Los Alamos, New Mexico.

After much difficulty, an absorbent barrier suitable for separating isotopes of uranium was developed and installed in the Oak Ridge gaseous diffusion plant. Finally, in 1945, uranium-235 of bomb purity was shipped to Los Alamos, where it was fashioned into a gun-type weapon. In a barrel, one piece of uranium was fired at another, together forming a supercritical, explosive mass. To achieve chain-reaction fission, a certain amount of fissile material, called critical mass, is necessary. The fissile material used in the Hiroshima model was uranium 235. In the bomb, the uranium was divided into two parts, both of which were below critical mass. The bomb was designed so that one part would be slammed into the other by an explosive device to achieve critical mass instantaneously (Badash 238). When critical mass is achieved, continuous fission (a chain reaction) takes place in an extremely short period of time, and far more energy is released than in the case of a gun-powder explosion (Badash 238). On December 2, 1942, the first self-sustaining chain reaction with cadmium took place, overseen by Enrico Fermi, in the University of Chicago squash fields (Asimov 783).

Another type of atomic bomb was also constructed using the synthetic element plutonium. Fermi built a reactor at Chicago in late 1942, the prototype of five production reactors erected at Hanford, Wash. These reactors manufactured plutonium by bombarding uranium-238 with neutrons. At Los Alamos the plutonium was surrounded with high explosives to compress it into a super dense, super critical mass far faster than could be done in a gun barrel. The result was tested at Alamogordo, New Mexico, on July 16, 1945, and was the first explosion of an atomic bomb code-named Trinity (Beyer 55).

However, all was not that easy coming up to this milestone point. Security restrictions bound both workers and townspeople. Everybody had the same address where all mail was censored (Wood 4). Everybody was restricted to a 200 mile radius, and residents of Los Alamos were prohibited from telling friends and relatives where they lived (Wood 4). There were serious issues of security of documents, due to failure to lock up (Wood 4).

The one serious incident was the hiring of Klaus Fuchs. He was later found, and convicted of obtaining secret documents and sending them to the Soviet Union. A competent and hardworking scientist himself, Fuchs enabled the Soviet Union to create their own atomic bomb (Beyer 45).

Names were not allowed to be mentioned outside of the laboratory. Everybody was a "sir" or "mister" instead of their own name (Wood 4). Unless they worked at the lab themselves, wives knew nothing of their husbands' research (Wood 4).

Decisions to drop the atomic bomb went through several personalities, yet ultimately rested upon president Truman. The man whose decisions created the Manhattan Project, never lived to see the results of his labor. FDR died on April 12, three months before the first successful Trinity test (Beyer 56). The responsibilities were soon placed upon Truman, the next president. Truman knew nothing about the bomb and its effects yet hastily decided that the bomb be used on Japan, considering Germany was no longer a target with the war in Europe over. Initiated by Szilard, a petition was made to offer the opinion that the bomb should be used only if Japan refused to surrender, even after being informed of the bomb's destructive capabilities (Beyer 65). Nevertheless, the decision was made that the bombs would be used until Japan surrendered.

The Hiroshima model is known as a gun-barrel-type atomic bomb. Due to its long and narrow shape, the Hiroshima model was called "Thin Man" at first, but during the manufacturing process the original plans were modified, shortening the length and giving rise to the name "Little Boy." (Beyer 48).The energy released from the Hiroshima A-bomb was originally thought to be equivalent to the destructive power of 20,000 tons of TNT. Later estimates, however, put the energy equivalent to approximately 15,000 tons of TNT, based on damage done to buildings and research on the bomb's composition. Despite the release of such enormous energy, it is believed that less than one kilogram of the 10 to 30 kilograms of uranium 235 housed in the bomb achieved fission.

The fissionable material used in the Nagasaki bomb was plutonium 239. The plutonium 239 was divided into below-critical-mass units and packed into a spherical case. At the time of detonation, the units were compressed to the center with a gun-powder explosion to achieve fission. The Nagasaki model is known as an implosion-type atomic bomb. Compared to the Hiroshima A-bomb, the one used in Nagasaki was larger in diameter and round so it was called "Fat Man." Only slightly more than one kilogram of the plutonium 239 is thought to have achieved fusion, but the energy released is estimated to be equivalent to the destructive power of about 20,000 tons of TNT (Hewlett 215).

Little boy killed about 100,000 people outright, wounded another 100,000, and destroyed about 90 percent of Hiroshima (Hewlett 216). Yet, while the first atomic bomb was a roaring success, it raised many ethical and controversial issues. Most of the people in the United States of America supported the use of the atomic bomb, even President Truman called it, "the greatest thing in history" (Beyer 75). Many people, including the scientists that developed the bomb, opposed the bombings and felt that it was immoral to kill that many innocent people just to get an influence in the war.

The Manhattan Project was one of the most important parts of American History. It was the first effort to create an atomic bomb, that helped end the war in the Pacific. I enjoyed researching the topic and learned a lot from my readings. Now I understand the atomic bomb better and also understand the motives behind it. Researching helped me understand the sheer strength and power of what a small element can do. All of our lives have changed through the development and bombing of the atomic bomb. The cold war, nuclear restrictions, nuclear energy, are all results of the first nuclear breakthrough. However, the controversial issues will still rage on. Nuclear testing, nuclear power, and nuclear waste are still being debated for over 50 years, and the United States, the only country to actually use the bomb, is the leader.

Works Cited