 James Cooley and John Tukey published a more general version of FFT in 1965 that is applicable when "N" is composite and not necessarily a power of 2.Tukey came up with the idea during a meeting of President Kennedy's Science Advisory Committee where a discussion topic involved detecting nuclear tests by the Soviet Union by setting up sensors to surround the country from outside.To analyze the output of these sensors, an FFT algorithm would be needed.