med 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 20,000
tons of TNT. The project was a success. They were an unprecedented
assemblage of civilian, and military scientific brain powerbrilliant, 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. 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. 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 fission or the
common isotope 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
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
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. 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,
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 . 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. 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.
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.
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. Everybody was restricted to a 200 mile
radius, and residents of Los Alamos were prohibited from telling friends and
relatives 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 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.
Names were not allowed to be mentioned outside of the laboratory. Everybody
was a “sir” or “mister” instead of their own name. Unless they worked at the
lab themselves, wives knew nothing of their husbands research
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. 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 bombs destructive capabilities. 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. 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.
Little boy killed about 100,000 people outright, wounded another 100,000, and
destroyed about 90 percent of Hiroshima. 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.”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 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. 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.
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.