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 ineztaneously (Badash

238). When critical mass is