Even at the time of the Manhattan Project, the vast majority of the cost, facilities and workers on the project were involved in creating the fissionable materi

Even at the time of the Manhattan Project, the vast majority of the cost, facilities and workers on the project were involved in creating the fissionable materials rather than the better-known design work at Los Alamos. Remember that even then, they were confident enough in the gun-type Little Boy design that they didn't even need to test it.