The Atomic Bomb:  Leaving an Impression on Scientific History

This website validates the impressive nature of the development of the Atomic bomb as part of scientific history. It will discuss the discoveries that scientists made throughout history that were vitally important to the project.  Additionally, this site will also cover the development of the Manhattan Project, including the different production facilities that existed. Lastly, this site will cover the testing of the first Atomic bomb.

             The development of the Atomic bomb is the most impressive scientific development in history.  The development of the bomb began with scientists working on independent projects, which climaxed with the Manhattan Project, and merged full strength with the testing at Trinity.  The background and history of the science that lead up to the Manhattan Project is important because it incorporates many ideas from prior decades. The Manhattan Project is the largest demonstration of the scientific community coming together ever. Hundreds and thousands of people and communities came together for one common goal, to end World War II.  Finally, the power and awe of this project itself was realized with the testing at Trinity. This marked the end of the Manhattan Project.  It is for these three reasons that the development of the Atomic bomb is the most impressive development in scientific history.

       The development of the Atomic bomb was impressive because it was an accumulation of decades of physics and chemistry. Before anyone ever thought or expressed ideas about mass production of atomic bombs, scientific groundwork had to be established. Forty years prior to the making of the Atomic bomb scientists were developing ideas that would later become the backbone of the Manhattan Project. Advances in physics and chemistry had to occur before the bomb could be produced. The exploration of radiation as well as the atom would eventually lead to the discovery of the Atomic bomb.

        Scientists of both physics and chemistry explored the mysterious properties of the atom.  In the late 1890’s Antoine Henri Becquerel (1852-1908) discovered the radioactivity of uranium. Radioactive elements emit radiant energy in the form of a (alpha), b (beta), g (gamma)  rays.  Following his discovery, in 1902 Marie Curie (1867-1934) and Pierre Curie (1859-1906) isolated the radioactive element radium. 

           

                                                                                    Bequerel                               Curie

        These two discoveries would soon become important when selecting a material for the bomb(3).  The discovery of the atom and its properties as well as the advances in physics enabled scientists to develop complex reactions. The famous Theory of Relativity by Albert Einstein (1879-1958) incorporates the ideas that small amounts of mass can be converted into vast amounts of energy. The equation E = mc˛, is based on the fact that the speed of light, c, is very fast and just a small amount of mass, m, can release large quantities of energy, E.  This concept set the stage for the discoveries of nuclear fission. Niels Bohr (1885-1962) performed experiments on the atom and proposed a picture of what the atom looks like, in 1913. This model suggested that the atom contains a nucleus at the center with rotating electrons. Bohr stated these electrons only orbit at specific distances. When electrons change distances toward the nucleus they emit radiation (4).

    

                                                                    Einstein                                    Bohr

          Radiation occurs in bursts since electrons can only change orbit in intervals. Ernest Rutherford (1871-1937) worked with Bohr on the atom and discovered that there was more that one type of atom and that it could be stable or unstable. The introduction of the neutron in 1932 by James Chadwick (1891-1974) added to a more complete description and understanding of the atom. The first signs of nuclear fission (the energy source for the Atomic bomb) came in 1934 when Enrico Fermi (1901-1954) and Irene Joliot-Curie (1897-1956) disintegrated heavy atoms by spraying them with neutrons. At this point these scientists did not realize that they had achieved fission. Otto Hahn (1879-1968) a German physicist performed the same experiments and is credited with discovering fission. He successfully split an atom. The splitting of an atom is based on Einstein’s E = mc˛ theory, were one atom splitting can cause large amounts of energy to be produced. With the discovery of uranium, Hahn, in 1938, was able to discover that the nucleus of uranium can be broken down easily to produce vast amounts of energy. When the nucleus is split energy is lost. This discovery alone would later have a tremendous effect on the world (3). 

           photo of Enrico Fermi     

                                        Rutherford                            Chadwick                        Fermi                                   Hahn

             With the discovery of fission many people thought this energy could be used for both good and bad. Einstein was one of Hahn’s friends and heard of his new discovery. Einstein knew this discovery would become very important and wrote a letter to President Roosevelt expressing his concern that the Germans were developing a new powerful bomb. In August of 1939, he instructed President Roosevelt to begin looking at ways of gathering this energy for a U.S. bomb before Germany did. This led to the start of the Manhattan Project.

              The Manhattan Project’s main purpose was to develop an effective method for mass production of atomic bombs. It was thought that hundreds of bombs would be needed in order to win the war and the only way to do this was to build powerful chemical and production facilities. Before these plants could be produced nuclear fission and uranium had to be understood.

              Nuclear fission is a reaction in which the nucleus of an atom is split into two equal fragments. From this reaction a 100 million volts of energy can be produced. This large amount of energy comes from the strong forces that hold the atom together. Because these forces are so strong it is difficult to split the nucleus of a stable atom. Uranium however is quite unstable and can be split easily. Uranium atoms have a difficult time staying together because they are so large (the largest natural element) and tend to want to split. Uranium will naturally decompose on its own over time. When this occurs radiation is emitted and the material turns to metal lead. Two isotopes of Uranium exist, U-238 and U-235. Both isotopes have 92 protons, but U-238 has 146 neutrons where U-235 has 143 neutrons. U-235 is the fissionable material needed for the complex fission reaction of the Atomic bomb. U-238 cannot be used because it will not split. Bombarding the nucleus with many neutrons splits U-235. When this happens a chain reaction develops. One neutron will split the one uranium nucleus into two parts, Barium and Krypton. Resulting from this is extra neutrons. These neutrons then interact with other U-235 molecules causing them to split.   This chain reaction takes place instantaneously and produces heat and gamma radiation (6).

       Obtaining pure enriched U-235 is a difficult task.  Uranium ore contains both U-238 and U-235, but separating these can be quite difficult. One obstacle with attaining U-235 is that such little of it exists in the world. Of all the Uranium in the world 99% of it is U-238 and only 1% is U-235. The Manhattan Project would spend a great deal of time and money on investigating ways to separate this precious metal (6).

      The development of the Atomic bomb is one of the most impressive scientific developments because of the immense effort put into the six years Manhattan Project. The speed at which this project took place as well as the joint efforts from many communities and companies allowed this project to occur. Secrecy was the top priority during this project, which added to its impressiveness. The Manhattan Project consisted of developing way to separate Uranium and construct a bomb mechanism.

        Once Uranium was split in 1938, efforts began on producing large amounts of the enriched U-235. Dr. Vannevar Bush of Scientific Research and Development coordinated the project. Once it was established that large amounts of Uranium could be produced President Roosevelt handed the project over the U. S. Army. Lieutenant Leslie Grooves was assigned as project leader in September of 1942. Lt.Leslie Grooves was responsible for coordinating and developing large-scale facilities that would mass produce the material needed for the Atomic bomb. A district was formed under Colonel James C. Marshall and Deputy Kenneth D. Nicholas and was called the Manhattan District or Project (1).

          Many of the years of the Manhattan Project were spent developing an adequate method for attaining and separating Uranium. Three known methods existed including gaseous diffusion, electromagnetic effects, and thermal diffusion. These three methods worked to separate small amounts of Uranium, but it was unclear whether or not they could operate at a large scale. The Manhattan Project scientists mainly focused their attention on separating Uranium through gaseous diffusion and electromagnetic effects. They also explored the use of Plutonium as another raw material for the Atomic bomb. Plutonium, or PU-239, is a fissionable material that can be produced from U-238. U-238 can be neutron saturated to produce Plutonium and it does not need to be separated (6). Plutonium was to be produced through the use of a graphite pile or reactor. The Uranium ore that was needed was difficult to find and large amounts were needed for the project. Twelve thousand tons of Uranium was purchased form Edgar Sengier and imported from the Belgian Congo. Sengier sold the Uranium at a discounted rate because he wanted to help the war effort although he was never told what this material was actually for. This Uranium supplied the project with its most essential raw material (1).

         Uranium and Plutonium became the center of the atomic bomb project. Lieutenant Groves approved two main sites for production of Uranium and Plutonium. These sites would be the center of atomic development. Oak Ridge, Tennessee became the site for separation of Uranium through gaseous diffusion and electromagnetic effects. And Hanford, Washington adopted the Plutonium project. 

         The facility at Oak Ridge was responsible for separating U-238 and U-235 while urgency and privacy were very important when constructing this facility. No one was allowed to know what was being built, including the workers. All they knew was that it was that it had to be done fast. The building of the Oak Ridge plant began before it was certain that gaseous diffusion or electromagnetics would even work on a large scale. Groves decided that the building of Oak Ridge must start as soon as possible because the United States may have to produce many bombs at once and they could not afford to wait for technology. Groves decided that large facilities needed to be built and technology would just have to catch up (1).

         Gaseous diffusion is a complex process that involves combining Uranium with fluorine to form a Hexafluoride gas. This mixture is then sent through porous barriers and the enriched uranium is extracted.  In 1942 this procedure could only separate micrograms of enriched Uranium. The building of the gaseous diffusion plant, code name K-25 for secrecy, could not wait for research to ensure a large-scale process building. The first thing at Oak Ridge that was built in 1943 was a powerful electric plant. The 34 million dollar power plant was built with 5,600 laborers in record time of ten months.  The actual K-25 plant was designed by a company named Kellex (Kelle for Kellego and X for secret).  Union Carbide was responsible for the building of the K-25 plant. The

Chrysler Company built the large metal diffusers for the gaseous diffusion plant. Chrysler took a large risk in building these diffusers because the diffusers had to be built out of nickel, which was in short supply, in order to withstand the strong Hexaflouride gas that occurred during the process.  If Chrysler did not produce the diffusers that were needed they would lose large amounts of money as well as their reputation.  Chrysler however was dedicated to helping end the war and devised a way to plate stainless steel with nickel.  Mass production of diffusers began and they were given the code name X-100. The construction of the chemical plant was difficult to build because Uranium chemistry was unknown.  Barriers and pumps were needed for the uranium separation process and two companies Houdaille-Hershey and Allis-Chalmers Company built them. The barriers were constructed in Decatur, Illinois and the pumps in Milwaukee, Wisconsin during the spring of 1943. The final plant was U-shaped spread over an area of two million square feet. It was half of a mile long and four hundred feet wide. All the companies involved in the gaseous diffusion plant took large risks because they did not know what they were building and they did not know if it would work (1).

            While the gaseous diffusion plant was being built, research was being conducted on the electromagnetic separation of Uranium.  Lt. Groves wanted to be sure that another method was available for separating Uranium in case gaseous diffusion could produce the needed quantities of enriched U-235.  The electromagnetic separation was discovered at the University of California, Berkley. This process involved a “calutron” which smashed atoms together through the use of a magnet. University of California could only produce micrograms of enriched U-235.  Scientists and engineers both had their doubts about a large scale electromagnet plant would operate (5).

             Stone and Webster, the U.S. Army’s general contractors, constructed the electromagnetic plant, code name Y-12.  A large amount of silver was needed to produce the massive coils and electrical conductors. The U.S. Treasury Department supplied the Manhattan Project with a thousand tons of silver for the project. The department was not even told anything about the project except that the silver was needed to help end the war.  The electromagnetic plant was large just like the gaseous diffusion plant.  The work force for both these plants included 20,000 people with a payroll of five million dollars per month. None of the workers at this plant had any idea they were separating Uranium for an atomic bomb (1).

              By 1944 the gaseous diffusion plant and the electromagnetic plant were not producing substantial amounts of enriched U-235. Lt. Groves decided to try another separation technique at Oak Ridge. A thermal diffusion plant, S-50 was built in 69 days. This large-scale process also did not produce a considerable amount of U-235. Scientists determined that if the electromagnetic plant was fed with some enriched material form the thermal diffusion plant it would produce U-235 (5). This was good because the construction of the thermal diffusion plant no longer became a mistake. Production of U-235 pushed on and material was sent to Los Alamos, New Mexico in July of 1945 (1).

 

                Besides the work that was occurring with the separation of Uranium, scientists were working on an effective way to produce vast amounts of Plutonium. Enrico Fermi amongst others produced the first successful chain reaction of Plutonium in Compton Laboratory at the University of Chicago in 1942. The reaction took place in a small graphite reactor.  Union Carbide chipped in to make the graphite. They stopped their own production in order to help the Manhattan Project.  Once this was proven to work a pilot plant was established at Oak Ridge with a graphite reactor, code-named X-10.  The X-10 reactor was kept secret and was used to run experiments and produce small amounts of Plutonium. The results from this reactor were used to build a Plutonium production facility in Hanford, Washington (5). 

      In 1943 Hanford was chosen as the site for a Plutonium production plant. Citizens living in Richland, Hanford, and White Bluffs, Washington were asked to vacate so that a production facility could be built on their 600 square miles of land. People were angry but understood that it had to be done in order to support the war effort. Dupont constructed the building.  Once again a company had to sacrifice their workers and reputation on a plant that was based solely on an idea. They accepted all of the risks. This Plutonium plant contained a lot of unknown risks because scientists were unsure how a large facility would operate. The Chicago pile and the Oak Ridge X-10 ran fine but it was a lot smaller than what was needed in Hanford. Many technical questions were unanswered (1).

         The construction of the plant was headed by Gilbert P. Church.  While he was running the plant he did not have any idea what it was for.  For this production facility the design and development was carried out at the same time the construction was. Church worked to organize 45,000 construction workers. In  Washington alone 29,762 people were recruited to work at Hanford. Precautions were taken not to hire anyone who lived in the Oak Ridge area. Secrecy was of the highest priority. 11,000 major pieces of equipment were gathered for the job. A town was built around the plant to occupy 400,000 people. It was like its own separate city (2).Exposing Uranium to reaction in an atomic reactor produced Plutonium. The material was allowed to sit for days until it was transformed into Plutonium. Three large reactors occupied Hanford and were cooled by water from a de-ionizing plant. In 1945 Plutonium was shipped to Los Alamos for construction of the Plutonium bomb (2).

        The building of Oak Ridge and Hanford was extremely impressive because it was highly secretive and involved many skilled scientists, engineers, and workers. Companies came together risking their own money and reputations to assist the military in ending the war. Companies such as Chrysler, Union Carbide, and Dupont interrupted their own processing to help the government. These companies and their workers were not told anything about the building of a bomb. In spite of this they still agreed to help. They took risks on safety and built these plants when there weren’t even sure if they would work. These plants were also impressive because they were built in record time. In a matter of three years Oak Ridge and Hanford were built. This is due to the fact that companies and the military cam together for one common goal.

         The final demonstration of the impressiveness of this scientific development was realized with the testing at Trinity, New Mexico. While plants were constructed for separating and producing Uranium and Plutonium, scientists were gathering at a laboratory to devise a way to produce a bomb. A mechanism for containing the chemical reaction was built at Los Alamos, New Mexico (1). Los Alamos, New Mexico was chosen by Lt. Groves as a site for the building of the bomb. The land was spacious and stretched for miles in an isolated section of the U.S.  No one lived on the land, thus no one had to move. Robert J. Oppenheimer was chosen in 1942 by Lieutenant Groves to head the project on bomb development. Oppenheimer personally hired a team of scientists to aid him in developing the bomb. Work began on the housing for the bomb in 1942. This was before it was even established that mass amounts of Uranium and Plutonium could be used. Groves did not want to fall behind the Germans in construction of the bomb so he pushed Oppenheimer to design a bomb quickly (1).

           A team of Army engineers built the Los Alamos facility. It was not as nice as the Oak Ridge and Hanford facilities. The government wanted a military laboratory with everyone in uniform. Some scientists disagreed stating that a scientific group organized along military lines would be too rigid. Scientists did not want rank to be used to distinguish between people; they felt that it would be an annoyance. Thus it became a civilian laboratory. In spite of these relationships between the scientific community and the Army were coupled with strain and irritation. The scientists felt that the laboratory was under too much surveillance. Their mail was read and telephone calls were limited. The military personal could not deal with the scientists not following the rules. As a result Los Alamos was segregated. This type of controversy was also seen in other in the other production plants. Physicists were disappointed to see the project handed over to the military and engineers because the scientists felt that they could not understand nuclear physics. The physicists had never worked with the engineers before and new working relationship had to be established. Despite all this controversy the Manhattan Project was a success.

     Two Bombs were developed at Los Alamos, one was made out of Uranium and one was constructed out of Plutonium. The Uranium bomb was named Little Boy and the Plutonium bomb was named Fat Man. Fat Man was to be tested at a located named Trinity. The Uranium bomb was not tested because not enough Uranium existed to make a test bomb and a real bomb. Trinity performed some early testing with explosives, which included some TNT and fissionable material from Hanford.  The atomic blast was expected to equal 5,000 tons of TNT. In the early morning of July 16, 1945, The Plutonium bomb was dropped at Trinity. Scientists observed the bomb from five to twenty miles away.  The first thing that was seen was a large bright light. Then thirty seconds later the air blast was experienced followed by a load roar one minute and thirty seconds later. The blast equaled roughly 10,000 tons of TNT. The building of the bomb was a complete success. Two weeks later on August 6, 1945 Little Boy was dropped on Hiroshima, Japan and three days later Fat man was dropped on Nagasaki, Japan (1).              

    With the testing at Trinity complete the development of the Atomic bomb was finalized. The combination of the scientific work before hand, the Manhattan Project itself, and the final testing at Trinity defines why development of the Atomic bomb is the most impressive scientific development in history. The accumulation of years of scientific research, thousands of man-hours, and millions of dollars, is what makes the development so impressive. The simple fact that no one was allowed to know how their contribution fit into the entire scheme yet they all came together perfectly is what makes it so impressive. The idea that companies were willing to sacrifice personal profits for the common goal of ending the war without knowing if the project would even work is also what makes this so extraordinary. It is for all these reasons that the development of The Atomic bomb is the single most remarkable scientific development in history.

By Megan Meintel, Spring 2001

 

 

References:  

Printed Materials

1. Groueff, Stephane. Manhattan Project: The Untold Story of the Making of the Atomic Bomb. Canada:Little Brown and Company, 1967. p3-362
2. Groves, Leslie R. Now it can be Told: The Story of the Manhattan Project. New York: Harper and Brothers, 1962. p 68-93
3. Lens, Sidney. The Bomb. New York: E.P. Dutton, 1982. p 4-10
4. Meadows, Jack. The Great Scientists. New York: Oxford University Press, 1987.
5. Rhodes, Richard. The Making of Atomic Bomb. New York: Sim and Schuster, 1986. p 394-395,  487-491, 547-548, 602

Web Sites

 6. http://www.student.nada.kth.se/~nv91-asa/atomic.html
 7. www.ornl.gov/graphite/graphite.html - Oak Ridge Reactor picture
8. www.atomicarchive.com/main.shtml- Fission picture, Trinity Map, Chicago Pile    
9. www.if.ufrj.br/famous/physlist.html- Scientist pictures
10. www2.lucidcafe.com/lucidcafe/lucidcafe/library/95nov/curie.html – Marie Curie picture
11. Search.gallery.yahoo.com/search/corbis?p=atomic+bomb – Fat Man and Little Boy pictures