COMPUTERS

• Cockroft-Walton Machines
• Computers
• Cyclotrons
• Experimental Reactors
• Mass Spectrometer
• The Dragon Machine

Computers and powerful calculators are so deeply integrated into today's science - indeed, into every aspect of today's world - that it can be difficult to imagine working without them. At the beginning of the Manhattan Project, however, the only "computers" available for the complex calculations necessary were teams of assistants using mechanical hand calculators. Scientists' wives at Los Alamos were enlisted, the work divided amongst them to maximize efficiency - one dedicated to adding, one to dividing, one to cubing, and so forth. This basic form of calculation worked well initially, but as calculations of neutron mean free paths, critical densities, and shockwave propagation grew ever more complex and time-intensive, it strained to produce results in a timely manner. Further, the scarcity of materials (especially radioactive materials) and scientific manpower means that extensive experimentation was impossible, so theoretical calculations were the only way to test central elements of the bomb designs before the final Trinity test. Los Alamos needed either far more teams of woman "calculators" or some new way of handling extensive calculations.

Luckily, a new set of technologies for handling just this sort of problem were emerging from university and corporate laboratories. International Business Machines (IBM), still a relatively small company, sold punch-card computing machines capable of these simple, repetitive calculations, and Los Alamos purchased several of them in September 1943. A John Henry-esque test pitted the human teams against the new machines, and the humans and their hand calculators kept up on the first day. Still, in the words of Richard Feynman, "the IBM machines didn't get tired and could work three shifts. But the girls got tired after a while." After Feynman innovated a color-coded punch-card system to allow parallel calculations, the IBM machines became effectively much faster still. Computers were an important part of the Manhattan Project from then onward.

This push towards embracing the latest computer technology was aided by the inclusion of one of the key pioneers of this field, the mathematician John von Neumann, in the Project. Von Neumann had several important contributions to the Manhattan Project in his role as a traditional "pencil and paper" mathematician, but it was also his knowledge of emerging computer technologies that led to the inclusion of such devices as the Mark I electromechanical calculator under development at Harvard. Even more revolutionary was the electronic numerical integrator and calculator (ENIAC) being developed at the University of Pennsylvania, a programmable machine which represented a leap of several orders of magnitude in computer power over earlier electromagnetic machines. ENIAC was initially designed to calculate artillery trajectories of the Army, but von Neumann saw additional needs in the problems of Los Alamos, and he developed a way to translate mathematical calculations into code usable by an ENIAC-like machine in 1944 and 1945.

During the war, the main contribution of these computers was in the design of the explosive lenses needed for the implosion device. As the war ended, the quickly improving computer technology became ever more important to nuclear weapon design. Von Neumann himself aided Edward Teller in using ENIAC to run calculations for Teller's proposed thermonuclear "super" bomb. Los Alamos worked to build its own mathematical analyzer, numerical integrator and computer, or MANIAC, in 1952, and soon developed the world's largest scientific computing center. The material shortages that made computers so vital for early atomic weapon design fell away after the war, but a new type of limitation emerged in the 1960s that once again increased the importance of computers in nuclear weapon design - political pressure and then international treaties aimed at limiting or eliminating live tests of nuclear weapons. Today, many design elements of nuclear weapons are tested exclusively in the vastly more powerful descendants of the hand calculators and IBM punch-card machines used by the Manhattan Project.

• Cockroft-Walton Machines
• Computers
• Cyclotrons
• Experimental Reactors
• Mass Spectrometer
• The Dragon Machine

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