One counterexample is Manhattan Project—they developed two different designs simultaneously because they weren’t sure which would work better. From wikipedia: Two types of atomic bombs were developed concurrently during the war: a relatively simple gun-type fission weapon and a more complex implosion-type nuclear weapon.https://en.wikipedia.org/wiki/Manhattan_Project#:~:text=The%20Manhattan%20Project%20was%20a,Tube%20Alloys%20project)%20and%20Canada.
Key point for those who don’t click through (that I didn’t realize at first) -- both types turned out to work and were in fact used. The gun-type “Little Boy” was dropped on Hiroshima, and the implosion-type “Fat Man” was dropped on Nagasaki.
One counterexample is Manhattan Project—they developed two different designs simultaneously because they weren’t sure which would work better. From wikipedia: Two types of atomic bombs were developed concurrently during the war: a relatively simple gun-type fission weapon and a more complex implosion-type nuclear weapon.
https://en.wikipedia.org/wiki/Manhattan_Project#:~:text=The%20Manhattan%20Project%20was%20a,Tube%20Alloys%20project)%20and%20Canada.
Key point for those who don’t click through (that I didn’t realize at first) -- both types turned out to work and were in fact used. The gun-type “Little Boy” was dropped on Hiroshima, and the implosion-type “Fat Man” was dropped on Nagasaki.