Why were Los Alamos scientists so confident “Little Boy” would work?

Question

The 1945 Trinity test was run to prove the complicated “Fat Man” design would even work. But why were scientists so confident of the “Little Boy” design that the didn’t feel the need to do a full test of the design? The design was simpler, but still, no one had ever done it before. Was it purely for time? Lack of materials? Or was the design and principles so sound, it couldn’t fail?

In: 11

Answer 1

because the type of reaction little boy used had accidentally been caused in labs when a critical mass was accidentally assembled and thankfully fell apart quickly.

the design was such overkill that there was almost no way it could fail.