No expert here; apparently this requires more / more enriched uranium. Since enriching uranium seems to be the bottleneck, this is suboptimal. This is why the H

No expert here; apparently this requires more / more enriched uranium. Since enriching uranium seems to be the bottleneck, this is suboptimal. This is why the Hiroshima bomb worked like this, but the second one, in Nagasaki, worked by compressing plutonium with explosives instead. There's also the question of "compactness". If you want to carry the bomb by plane, say, it has to be light-ish and compact-ish, which this design lends itself less to. If you want to shoot it up in a rocket, this is even more important.