The Manhattan Project needed lots of computers for such things as design, explosive yield, the physics of implosion, and more. At the time “computers” usually meant a woman whose job was to perform calculations by hand or with a mechanical calculator, the Marchant. Women with degrees in math and science often took jobs as computers because of discrimination in their own fields. As such, many of the women who became computers for the Manhattan Project were grossly overqualified for these jobs.
By 1943, about 20 computers worked in the T-5 Computation group at Los Alamos, under the supervision of Mary Frankel, wife of Stanley Frankel, who, with Eldred Nelson, organized the computing program. The wartime mechanical calculators were integral to the project, but lacked mechanical reliability and required routine repairs. Richard Feynman and Nicholas Metropolis started repairing the Marchant machines as an extracurricular activity and grew more adept at maintaining them, enabling the scientific staff to model complex experiments. Metropolis would later build the MANIAC computer at Los Alamos from a design by John von Neumann.
The Marchant calculator on display at the Los Alamos History Museum is a Figurematic from the 1950s. The women computers at Los Alamos would have worked on Marchant Silent Speed calculators, first developed in 1932, and continuously improved until the Figurematic line which was produced until the business closed in the early 1970s.