During the World War II the united sates used an unprecedented $2 billion to feed an ultra-secret research and development program, the outcome of which would alter the relationships of nations forever. Known as the Manhattan project, it was the search by the United States and her closest allies to create a practical atomic bomb. It is a single device which capable of mass destruction, the threat of which alone could be powerful enough to end the war. The motivation was simple. Scientists escaping the Nazi regime had revealed that research in Germany had confirmed the theoretical viability of atomic bombs. In 1939, in support of their fears that the Nazis might now be developing such a weapon, Albert Einstein and others wrote to President Franklin D. Roosevelt (FDR) warning of the need for atomic research. By 1941 FDR had authorized formal, coordinated scientific research into such a device. Among those efforts would ultimately unleash the power of the atom was Robert Oppenheimer, who was appointed the project’s scientific director in 1942. Under his direction the famous laboratories at Los Alamos would be constructed and the scientific team assembled. On July 16 1945, in a small town called Alamogordo, New Mexico, the course of human history was changed; the first atomic bomb was detonated that day.
Principle of an atomic bomb
An atom bomb works in the principle that when you break up a nucleus of an atom, a large amount of energy is released. Because it takes a large amount of energy to keep the nucleus bound together. When you split it apart, the energy is released. Scientists chose the biggest and heaviest nucleus that is found in nature to be the best object for splitting. It is uranium, it is unique in that one of its isotopes is the only naturally occurring element on that is capable of sustaining a nuclear fission reaction. A uranium atom has 92 protons and 146 neurons together to give an atomic mass of 238 or U238. A very small portion of uranium, when it is mine, is in the form of an isotope U235, this isotope has the same 92 protons but only 143 neutrons, or three fewer than U238. U235 is highly unstable, which makes it highly fissionable. When uranium U235 is slammed by a neutron, it becomes uranium 236. In the process of splitting and creating two more stable atoms, a whole bunch of energy is released, along with three more neutrons. These three more neutrons fly out and slam more U235 atoms. And thus, a chain reaction occurs, causing more and more U235 to be split, and ultimately causes a huge explosion. The uranium contains only 0.7% of this U235 isotope, and a whole bunch of it is needed to make one atomic bomb.
Another engineering challenge is to create a vessel with the correct shape and material to contain the neutrons after fissioning, so that they do not escape, but rather cause more atoms to fission. And it is lined with a special mirror so that it forces neutrons back in to the fissionable material rather than escape the vessel. Then the correct amount of fissionable material has to be placed inside this vessel. This is called ‘super critical mass’. There has to be enough mass to sustain an uncontrollable chain reaction resulting in an explosion. The super critical mass has to be kept apart until you are ready for an explosion. Otherwise an explosion can occur when you don’t want it. The reason is because these isotopes are unstable, and are throwing off neurons randomly. In an atomic bomb, two sub-critical masses are slammed together usually with a conventional bomb contained inside the outer bomb. This conventional explosive charge initiates the chain reaction. This project ultimately created the first, man-made nuclear explosion, which Robert Oppenheimer called “trinity” on July 16, 1945. The concept of an atom bomb is simple but, the process of actually creating a bomb is not so simple.
“Now I am became Death, the destroyer of worlds.” – J. Robert Oppenheimer