I roto i te 1941, ki te Pakanga Tuarua o te Ao riri i roto i Europe, engari i te United States kahore ano i roto i te whawhai, Feynman pau te raumati mahi i runga i ngā raruraru ballistics i te Frankford Arsenal i Pennsylvania. I muri i te whakaeke i runga i Pearl Harbor i kawea te United States ki te whawhai, Feynman i tonoa e Robert R. Wilson, i te mahi i runga i tikanga ki te whakaputa i te uranium whakarei mō te whakamahi i roto i te poma karihi, hei wāhanga o te aha e riro i te Manhattan Project. i te rōpū o Wilson i Princeton i te mahi i runga i te pūrere i huaina he isotron, tikanga ki te wehe electromagnetically uranium-235 i uranium-238. i mahi i tenei i roto i te tikanga rawa rerekē i te mea i whakamahia e te calutron i i raro i te whanaketanga e te rōpū i raro i te kaiako o mua o Wilson, Ernest O. Lawrence, i te Laboratory Radiation o te California. i runga i te wā, ko te tino pai te Calutron Ultimate i roto i Los Angeles. i roto i roto i te pakanga o te
te whakatakoto i ngā tikanga haumaru mō te rokiroki rauemi