“I was an unusual theorist in that my greatest strength was… seeing how theory and experiment related.”
Introduction
Born on May 14, 1916, the great Canadian-American Physicist Robert Frederick Christy was a major player in the development of the atomic bombs. His service as a theoretical physicist during the Manhattan Project would lead to the successful creation of a working plutonium-based atomic bomb.
Early Life
Robert Christy’s humble beginnings started as an orphan in Vancouver. However, his life would soon turn towards the better when he received the Governor General’s Gold Medal at age 16. This allowed him to skip the remainder of high school to attend the University of British Columbia as a sophomore. Within 3 years, he would complete his Bachelor’s degree in physics and additional 2 years, his Master’s in Physics and Mathematics. Afterwards, he traveled to the University of California at Berkeley, where he met Robert J Oppenheimer, the leading theoretical physicist at the time. Working under Oppenheimer as a graduate student, Christy would receive his doctorate’s degree in 1941 and be immediately hired as a physics professor at the Illinois Institute of Technology. During the fall of that year, he was invited to join the Manhattan Project and work with Enrico Fermi to build the first nuclear reactor. By the winter of 1942, they’d succeeded in creating Chicago Pile-1, the world’s first working nuclear reactor. And finally, in 1943, Oppenheimer would invite Robert to work at the Los Alamos research center for the development of the atomic bombs.
Manhattan Project
Under Hans Bethe, the head of the Theoretical Division in Los Alamos, Robert Christy’s first role was to aid in the development of an aqueous homogeneous reactor. This would test critical mass calculations and the effect of various tamper materials, with a strong emphasis on enriched uranium. Robert would help regain confidence within the Theoretical Division when his prediction of enriched uranium’s critical mass had a mere 1.7% error.
His key contribution, however, was the development of the Christy Pit. The previous design of the plutonium-based bomb could not deal with jets and spalling during the bomb’s drop as they would cause the hollow sphere of plutonium to change shape and prevent the nuclear blast. Robert Christy had an ingenious idea to use an ultraconservative design; he proposed using an almost solid sphere of plutonium slightly less than critical mass, with a small central cavity holding an “initiator” to supply neutrons to get the fission reaction started. When compressed hard enough, the atoms would be forced close enough to achieve critical mass, triggering the chain reaction and nuclear blast. His design would be used in “The Gadget” during the Trinity Bomb Test and in the “Fat Man” bomb during the Nagasaki bombing.
After the War
After the war, Christy would return to the University of Chicago where he became an assistant professor of physics. Soon after, however, he was invited to join the faculty at Caltech in 1946 by Oppenheimer. He turned his research towards astrophysics, where he assisted in creating some of the first computational models of stellar operation. Perhaps his most notable project was Project Orion, which investigated whether or not a spacecraft could be efficiently propelled by a series of controlled nuclear blasts behind the craft, a process known as nuclear pulse propulsion. For his work, he was awarded the Eddington Medal of the Royal Astronomical Society in 1967. Meanwhile, Christy would also be a large proponent of anti-nuclear warfare. In 1945, he became one of the founding members of the Association of Los Alamos Scientists to educate the public on the peaceful uses of atomic energy. He also aided in the studying of the radiation effects of the Hiroshima and Nagasaki bombs. Robert would be named the vice president and provost of Caltech in 1970, and in 1977, briefly become president of Caltech for a year. Unfortunately, he died on October 3, 2012, at the age of 96 in Pasadena, California. His work during the Manhattan Project will always be remembered for its importance in contributing invaluable information towards the development of the atom bomb.
-Timothy Lo
Sources
- Broad, William J. “Robert F. Christy, Atom Bomb Physicist, Dies at 96.” The New York Times, The New York Times, 4 Oct. 2012, www.nytimes.com/2012/10/05/science/robert-f-christy-atom-bomb-physicist-dies-at-96.html?ref=obituaries.
- Christy, Juliana. “Robert F. Christy (1916 – 2012).” Robert F. Christy (1916 – 2012) | American Astronomical Society, American Astronomical Society, 2012, aas.org/obituaries/robert-f-christy-1916-2012.
- Lippincott, Sara. “Robert F. Christy.” Caltech Oral Histories Library, Archives California Institute of Technology, 22 June 1994, oralhistories.library.caltech.edu/129/1/OH_Christy_R.pdf. Accessed 4 Jan. 2018.
- Los Angeles Times Staff and Wire Reports. “Robert F. Christy Dies at 96; Manhattan Project Physicist – LA Times.” Los Angeles Times, Los Angeles Times, 5 Oct. 2012, www.latimes.com/local/obituaries/la-me-robert-christy-20121006-story.html.
- Svitil, Kathy. “Noted Physicist Robert F. Christy Dies | Caltech.” The California Institute of Technology, The California Institute of Technology, 3 Oct. 2012, www.caltech.edu/news/noted-physicist-robert-f-christy-dies-36918.