In June 1943 , Parsons joined the Manhattan Project as Associate Director at the research laboratory at Los Alamos , New Mexico under J. Robert Oppenheimer . Parsons became responsible for the ordnance aspects of the project , including the design and testing of the non-nuclear components of nuclear weapons . In a reorganization in 1944 , he lost responsibility for the implosion-type fission weapon , but retained that for the design and development of the gun-type fission weapon , which eventually became Little Boy . He was also responsible for the delivery program , codenamed Project Alberta . He watched the Trinity nuclear test from a B-29
Trinity nuclear test
Trinity (nuclear test)
William Sterling Parsons