Los Alamos: Beginning of an Era 1943-1945

Part II

Trinity

Development of the gun-type uranium weapon, which was to become “Little Boy”, moved confidently ahead, but work on implosion (the method in which a subcritical mass of plutonium is compressed to supercriticality by high explosives) was slow, frustrating and often seemingly hopeless. By late 1943 it was evident that there was no alternative: the implosion device would have to be tested.

If it were not, too many questions would be left unanswered. A nuclear explosion was so entirely new, the implosion method so far removed from any existing practice, the construction of the atom bomb so entirely dependent on dead reckoning, that no one was willing to risk the first trial of such a device over enemy territory or even in demonstration for the Japanese, as had been suggested, where a failure would wipe out the crucial psychological effects of so monumental a weapon.

Furthermore, it was essential to obtain detailed and quantitative information on the various effects of the new weapon which would serve as basic technical data for tactical planning in the future. Little of this could be obtained if the explosion were first observed under combat conditions.

One important question, about which there was substantial disagreement, concerned the explosive force to be expected. Only an actual nuclear detonation could settle that question, and then only if meaningful measurements (requiring many new techniques) could be made.

Other questions concerned the performance of the implosion system inside the device; the destructive effects of heat, blast, and earth shock; radiation intensities; fallout; and general phenomena (fireball, cloud, etc.) associated with the explosion.

And so the decision was made to sacrifice what was to amount to one third of the nation’s stockpile of atomic weapons and its entire supply of plutonium on a secret test on American soil.

---