Mark I worked around the clock on military projects, calculating massive mathematical tables. Principally it helped the Navy by computing tables for the design of equipment such as torpedos and underwater detection systems. Other branches of the military sought its help in calculating the design of surveillance camera lenses, radar, and implosion devices for the atomic bomb in the Manhattan Project.
The mathematical tables that Mark I churned out were the first of their kind: They were printed directly from a machine’s output, eliminating all human error. One of the computer’s longest running projects required it to solve a set of differential equations called Bessel Functions. As a result, the computer was given the nickname “Bessie.”