The U.S. funded an exercise back in, iirc, the 60s of getting a few physics grad students to design a fission bomb using only open-source info. (That's far less

The U.S. funded an exercise back in, iirc, the 60s of getting a few physics grad students to design a fission bomb using only open-source info. (That's far less resources than modern Japan could give it.) They succeeded at coming up with a viable implosion design.