The Making of the Atomic Bomb: 25th Anniversary Edition

by Richard Rhodes

A formal status report went off immediately from the Executive Committee to Bush. It predicted enough fissionable material for a test in eighteen months—by March 1944. It estimated that a 30-kilogram bomb of U235 “should have a destructive effect equivalent to the explosion of over 100,000 tons of TNT,” much more than the mere 2,000 tons estimated earlier. And it dramatically announced the Super: If this [U235] unit is used to detonate a surrounding mass of 400 kg of liquid deuterium, the destructiveness should be equivalent to that of more than 10,000,000 tons of TNT. This should devastate an area of more than 100 square miles. The committee—Briggs, Compton, Lawrence, Urey, Eger Murphree and Conant—concluded by judging the bomb project important beyond all previous estimates: “We have become convinced that success in this program before the enemy can succeed is necessary for victory. We also believe that success of this program will win the war if it has not previously been terminated.” On August 29 Bush bumped the status report up to the Secretary of War, noting that “the physicists of the Executive Committee are unanimous in believing that this large added factor [i.e., the Super] can be obtained. . . . The ultimate potential possibilities are now considered to be very much greater than at the time of the [last] report.”1637 The hydrogen bomb was thus under development in the United States onward from July 1942.