The First Designs
The scientists working on the project had two main designs they thought would work. By the spring of
1944 the scientists had finalized the designs, one with a core of plutonium, the other with a core of
U-235 - both the size of a baseball. The bomb using U-235 was called "Little Boy" and was ten feet long
and 2 feet tall. Little Boy worked by shooting a uranium buttet into the uranium core, creating critical
mass and setting off a chain reaction. There more complicated bomb was "Fat Man", an implosion device
eleven feet long and five feet tall. For it to work explosives surroiunding the plutonium all had to
go off at the same time, compressing the plutonium to critical mass and starting a chain reaction.
Many scientists believed Little Boy would explode but no one was sure about Fat Man, so they decided to
test it. Groves looked for a place to test the bomb and found one, a place near Alamagordo, New Mexico
in the desert.