Doesn't everyone studying for a bachelor's degree in applied physics have to work out things like critical mass and how to avoid premature explosion?
At least we did when I was studying for my Applied Physics degree in the mid 70s. It was not regarded as even slightly controversial that we should do so nor that it was especially difficult. It was simply one of the problems set in the nuclear physics course.
Of course we didn't go into the same degree of detail as Dobson, Pipkorn, and Selden and our solutions would probably not have been as effective but that was mostly because it was the thought process rather than the ultimate result that was important.
I had a first year’s physics class where we convinced our professor to walk through how to create a nuclear bomb of the two main types.
He was a young physicist at the Manhattan Project and told us stories of that as well… like the worry of igniting the oxygen of the planet’s atmosphere, how he didn’t worry being at blast site but grew concerned the farther he got (but inside dangerous radius), how the guards lost their shit and dropped their guns and ran when it went off (and the physicists cheer and looked at the panels instead of the slit window).
Well the trick is to ensure that the mass only becomes critical right when you want it to. So -- I imagine -- most of the work in making a working atomic bomb is more about the precisely-controlled explosions that detonate it, not the fission itself.
Gun-type bombs like Little Boy used in Hiroshima are less efficient, but much simpler. Shoot an enriched uranium projectile into an enriched uranium target, such that the combined volume they compress to is supercritical.
At least we did when I was studying for my Applied Physics degree in the mid 70s. It was not regarded as even slightly controversial that we should do so nor that it was especially difficult. It was simply one of the problems set in the nuclear physics course.
Of course we didn't go into the same degree of detail as Dobson, Pipkorn, and Selden and our solutions would probably not have been as effective but that was mostly because it was the thought process rather than the ultimate result that was important.