The dropping of the atomic bombs during World War II is one of the most widely known moments in history. While many accounts focus on the science and moral questions surrounding nuclear weapons, few give detailed insight into the technical and practical problems associated with nuclear weapon development from 1941 to 1945. Richard Groves, the director of the Manhattan Project, the program in the United States that produced the first atomic bomb, said, “We had the full backing of our government, combined with the nearly infinite potential of American science, engineering and industry, and an almost unlimited supply of people endowed with ingenuity and determination.” Groves was aware of the cooperation among science, engineering, industry, and military necessary for the success of the Manhattan Project. In this essay, I will argue that the United States built the first atomic bomb by making advances in theoretical and applied sciences. I will support this argument by discussing the human, scientific, material, and financial resources that were deployed throughout several stages of the bomb development.
The origins of nuclear weapons began with theoretical physics. In 1939, Austrian scientists Otto Frisch and Lise Meitner discovered the phenomenon of nuclear fission. They demonstrated that bombarded uranium nuclei could split into two fragments, accompanied by the release of energy. Furthermore, they found that each fission released additional neutrons, raising the possibility of a self-sustaining chain reaction.
After the theory of fission was established, it took two years for the United States government to apply the theory for military use. Prompted by a letter from Leo Szilard and Albert Einstein, President Roosevelt authorized research on the feasibility of an atomic bomb on October 9, 1941. Physicists studied chain reactions, as well as methods of isotope separation (uranium has two abundant isotopes- U235 and U237, of which only U235 is fissile). They discovered a new radioactive isotope, plutonium, which was more fissile than U235. The practicality of atomic bombs was established in 1942, when Enrico Fermi achieved the first self-sustaining chain reaction. Fermi provided the proof-of-concept needed to secure additional government funding: $160 million was allocated to construct industrial-scale plutonium, and an additional $20 million toward heavy water production plants, with a total estimated cost of $400 million.
Following Fermi’s chain reaction, scientists turned to industry to supply the plutonium and U235 needed to design nuclear weapons. Production of U235 took place at Oak Ridge, Tennessee. Engineers designed calutrons to separate uranium isotopes, which required over 22,000 operators. Additionally, the calutrons required over 86,000 tons of high quality electrical conductors. The method produced 1 kg of 90% pure U235 per day, at a total construction cost of $26 million. The planned technical project at Oak Ridge demonstrated the vital role of engineers, laborers, and materials in producing the atomic bomb.
While production of U235 occurred at Oak Ridge, theoretical and applied scientists in Los Alamos, New Mexico, conducted research on bomb logistics. Five division were created: theory, experimental physics, chemistry, ordnance and engineering, and administration. These divisions demonstrate the diverse array of scientists, engineers, and military officials needed for the operation. Work at Los Alamos focused on three components of weapon production: 1) gun design, 2) initiator design, and 3) implosion. In developing gun design, engineers created a cannon that could fit inside a bomb so that a sub-critical piece of U235 could be fired into another to detonate the bomb. Additionally, a polonium initiator was needed to produce neutrons to start the chain reaction. The government used industrial resources and contracted Monsanto to coordinate polonium production. Finally, the implosion program was developed for the plutonium bomb. Two new divisions, gadget (G) and explosives (X), used a blanket of explosives to crush a shell of fissile material in on itself, thus creating a critical mass and explosion. The gun design, initiator design, and implosion projects at Los Alamos demonstrate intimate coordination among physicists, engineers, laborers, and military officials.
To test their designs, engineers used instrumentation and complex materials. High-speed cameras, x-rays, and magnetism were used to test high-explosive castings for the bombs. The castings contained over a hundred pieces, and expert metallurgists had to weld them within a precision of a few thousandths of an inch. On July 16, 1945, the researchers were ready to test the plutonium bomb. The successful test was a monumental accomplishment, combining the efforts of theoretical and practical scientists, as well as the efforts of industrial workers who had supplied tons of raw materials.
The final aspect of the project involved preparations for dropping the bomb, and brought together aspects of military, infrastructure, and science. It took place at Tinian, an island off the coast of Japan. The island was conquered by an assault of 40,000 U.S. soldiers in June 1944. The U.S. quickly developed infrastructure on Tinian, turning it into the largest airport in the world. Two divisions were created: 1) a civilian arm of scientists and technicians who assembled the nuclear devices, and 2) a military arm of 50,000 soldiers and pilots who delivered the bombs. At Tinian, infrastructure provided the final link between scientists and military, so that an atomic bomb could be assembled and delivered. On August 6, 1945, Enola Gay departed from Tinian and dropped the first atomic bomb on Hiroshima.
The development of the atomic bomb during World War II was a complicated project that could not be accomplished with theoretical physics alone. The Manhattan Project required cooperation among theoretical and practical scientists, laborers, industry, military forces, and government administration. Overall, the Manhattan Project employed 130,000 workers, cost $2 billion, and utilized tons of raw materials. Thus, the Manhattan Project exemplified science at an unprecedented scale, and introduced the link between science and government known as “Big Science”. The project “demonstrated that a well-funded, large-scale, mission-oriented, multi-disciplinary research laboratory employing the new blend of pre-war and Manhattan Project strategies could handle a problem that only one year earlier had looked impossible.” Thus, the human, scientific, material, and financial resources of the Manhattan Project demonstrate how the U.S. made advancements in both theoretical and practical sciences to create the first atomic bomb.