The Enola Gay flew overthe 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 20,000tons of TNT. The project was a success. They were an unprecedentedassemblage of civilian, and military scientific brain powerbrilliant, intense,and young, the people that helped develop the bomb.
Unknowingly they cameto an isolated mountain setting, known as Los Alamos, New Mexico, to designand build the bomb that would end World War 2, but begin seriouscontroversies concerning its sheer power and destruction. I became interestedin this topic because of my interest in science and history. It seemed anappropriate topic because I am presently studying World War 2 in my SocialStudies Class.
The Hiroshima and Nagasaki bombings were always taught tome with some opinion, and I always wanted to know the bomb itself and theunbiased effects that it had. This I-search was a great opportunity for me toactually fulfill my interest. The Manhattan Project was the code name for the US effort during World WarII to produce the atomic bomb. It was appropriately named for the ManhattanEngineer District of the US Army Corps of Engineers, because much of theearly research was done in New York City.
Sparked by refugee physicists inthe United States, the program was slowly organized after nuclear fission wasdiscovered by German scientists in 1938, and many US scientists expressed thefear that Hitler would attempt to build a fission bomb. Frustrated with the ideathat Germany might produce an atomic bomb first, Leo Szilard and otherscientists asked Albert Einstein, a famous scientist during that time, to use hisinfluence and write a letter to president FDR, pleading for support to furtherresearch the power of nuclear fission. His letters were a success, and PresidentRoosevelt established the Manhattan Project.
Physicists from 1939 onward conducted much research to find answers to suchquestions as how many neutrons were emitted in each fission, which elementswould not capture the neutrons but would moderate or reduce their velocity ,and whether only the lighter and scarcer isotope of uranium fission or thecommon isotope could be used. They learned that each fission releases a fewneutrons. A chain reaction, therefore, was theoretically possible, if not toomany neutrons escaped from the mass or were captured by impurities. To createthis chain reaction and turn it into a usable weapon was the ultimate goal of theManhattan Project.
In 1942 General Leslie Groves was chosen to lead the project, and heimmediately purchased a site at Oak Ridge, Tenn., for facilities to separate thenecessary uranium-235 from the much more common uranium-238. Uranium235 was an optimal choice for the bomb because of its unusually unstablecomposition. Thus, the race to separate the two began. During that time, thework to perfect the firing mechanism and structure of the bomb was alsoswiftly underway.
General Groves initial task had been to select a scientific director for the bombproject. His first two choices, Ernest O. Lawrence, director of theelectromagnetic separation project, and Arthur H. Compton, director ofChicago Metallurgical Laboratory, were not available. Groves had some doubtsregarding the next best candidate, J. Robert Oppenheimer. Finally, Grovesgambled on Oppenheimer, a theoretical mathematician, as director of theweapons laboratory, built on an isolated mesa (flat land area) at Los Alamos,New Mexico. After much difficulty, an absorbent barrier suitable for separating isotopes ofuranium 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 ofuranium was fired at another, together forming a supercritical, explosive mass.
To achieve chain-reaction fission, a certain amount of fissile material, calledcritical mass, is necessary. The fissile material used in the Hiroshima modelwas uranium 235. In the bomb, the uranium was divided into two parts, both ofwhich were below critical mass. The bomb was designed so that one part wouldbe slammed into the other by an explosive device to achieve critical massinstantaneously .
When critical mass is achieved, continuous fission (a chainreaction) takes place in an extremely short period of time, and far more energyis released than in the case of a gun-powder explosion. On December 2, 1942,the first self-sustaining chain reaction with cadmium took place, overseen byEnrico Fermi, in the University of Chicago squash fields.
Another type of atomic bomb was also constructed using the synthetic elementplutonium. Fermi built a reactor at Chicago in late 1942, the prototype of fiveproduction reactors erected at Hanford, Wash. These reactors manufacturedplutonium by bombarding uranium-238 with neutrons. At Los Alamos theplutonium was surrounded with high explosives to compress it into a superdense, super critical mass far faster than could be done in a gun barrel. Theresult was tested at Alamogordo, New Mexico, on July 16, 1945, and was thefirst explosion of an atomic bomb code-named Trinity.
However, all was not that easy coming up to this milestone point. Securityrestrictions bound both workers and townspeople. Everybody had the sameaddress where all mail was censored. Everybody was restricted to a 200 mileradius, and residents of Los Alamos were prohibited from telling friends andrelatives where they lived. There were serious issues of security of documents,due to failure to lock up. The one serious incident was the hiring of KlausFuchs. He was later found, and convicted of obtaining secret documents andsending them to the Soviet Union. A competent and hardworking scientisthimself, Fuchs enabled the Soviet Union to create their own atomic bomb.
Names were not allowed to be mentioned outside of the laboratory. Everybodywas a “sir” or “mister” instead of their own name. Unless they worked at thelab themselves, wives knew nothing of their husbands researchDecisions to drop the atomic bomb went through several personalities, yetultimately rested upon president Truman.
The man whose decisions created theManhattan Project, never lived to see the results of his labor. FDR died onApril 12, three months before the first successful Trinity test. Theresponsibilities were soon placed upon Truman, the next president. Trumanknew nothing about the bomb and its effects yet hastily decided that the bombbe used on Japan, considering Germany was no longer a target with the war inEurope over. Initiated by Szilard, a petition was made to offer the opinion thatthe bomb should be used only if Japan refused to surrender, even after beinginformed of the bombs destructive capabilities.
Nevertheless, the decision wasmade that the bombs would be used until Japan surrendered.The Hiroshima model is known as a gun-barrel-type atomic bomb. Due to itslong 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.
The energyreleased from the Hiroshima A-bomb was originally thought to be equivalent tothe destructive power of 20,000 tons of TNT. Later estimates, however, put theenergy equivalent to approximately 15,000 tons of TNT, based on damage doneto buildings and research on the bomb’s composition. Despite the release ofsuch enormous energy, it is believed that less than one kilogram of the 10 to 30kilograms of uranium 235 housed in the bomb achieved fission.
The fissionable material used in the Nagasaki bomb was plutonium 239. Theplutonium 239 was divided into below-critical-mass units and packed into aspherical case. At the time of detonation, the units were compressed to thecenter with a gun-powder explosion to achieve fission. The Nagasaki model isknown as an implosion-type atomic bomb. Compared to the HiroshimaA-bomb, the one used in Nagasaki was larger in diameter and round so it wascalled “Fat Man.” Only slightly more than one kilogram of the plutonium 239is thought to have achieved fusion, but the energy released is estimated to beequivalent to the destructive power of about 20,000 tons of TNT.
Little boy killed about 100,000 people outright, wounded another 100,000, anddestroyed about 90 percent of Hiroshima. Yet, while the first atomic bomb wasa roaring success, it raised many ethical and controversial issues. Most of thepeople in the United States of America supported the use of the atomic bomb,even President Truman called it, “the greatest thing in history.”Many people,including the scientists that developed the bomb, opposed the bombings and feltthat it was immoral to kill that many innocent people just to get an influence inthe war.
The Manhattan Project was one of the most important parts of AmericanHistory. It was the first effort to create an atomic bomb, that helped end thewar in the Pacific. All of our lives have changed through the development andbombing of the atomic bomb. The cold war, nuclear restrictions, nuclearenergy, are all results of the first nuclear breakthrough. However, thecontroversial issues will still rage on. Nuclear testing, nuclear power, andnuclear waste are still being debated for over 50 years, and the United States,the only country to actually use the bomb, is the leader.
- Asimov, Isaac. Asimovs Biographical Encyclopedia of Science ;Technology. 2nd ed. New York: Double day, 1978.
- Badash, Lawrence. “Manhattan Project.” Dictionary of American History. Vol. 4. New York: Charles Scribers Sons, 1976.
- Beyer, Don. The Manhattan Project. New York: Franklin Watts, 1991. Hewlett, Richard. “Atomic Bomb.” Dictionary of American History. Vol. 1. New York: Charles Scribers Sons, 1976.
- Wood, Linda. “Men and Mission of the Manhattan Project.” World War 2. Jul. 1995: 38-45. SIRS Researcher. CR computer network. SIRS, 1995.