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. 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
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. 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 . 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