Page "Trinity (nuclear test)" Paragraph 12

The impossibility of solving this problem of a gun-type bomb with plutonium was decided upon in a meeting in Los Alamos on June 17, 1944.

This forced a search for a different, more practical design of a plutonium-fueled bomb, and an implosion-type atomic-bomb design ( i. e., the Fat Man design ) was selected as the most practical one at that time.

However, even this notion required a great deal of research work and experimentation in engineering and hydrodynamics before a practical design could be worked out.