The properties of pure uranium-235 were relatively unknown, as were those of plutonium, an element that had only been discovered in February 1941 by Glenn Seaborg and his team.
As propiedades do uranio-235 puro eran relativamente descoñecidas, igual que as do plutonio, elemento que fora descuberto en febreiro de 1941 por Glenn Seaborg e o seu equipo.