1945 May 31
Critical mass tests with plutonium begin at Los Alamos, NM.
Critical mass tests with plutonium begin at Los Alamos, NM.
Secretary of War Henry Stimson rules out Kyoto, the ancient capital of Japan, as a target for atomic attack.
Target Committee meets with Lt. Col. Paul Tibbets in attendance. The meeting reviews preparation for delivering atomic bombs, and status of conventional bombing of Japan. Tibbets estimates that by Jan. 1, 1946 all major cities of Japan will have been destroyed by fire bombing. The target list is now Kyoto, Hiroshima, and Niigata.
464 B-29s raid Tokyo again, burning out nearly 16 square miles of the remaining city. Only a few thousand are killed, urban inhabitants have learned to flee fire bomb attacks quickly and escape the flames. Also, Operation OLYMPIC, the invasion of Kyushu (the southern Japanese island), is set for November 1.
Little Boy is ready for combat use, except for the U-235 core. It is estimated sufficient material will be available by 1 August.
Target Committee reconvenes. On the committee now are J. Robert Oppenheimer, John von Neumann, Deak Parsons, and Hans Bethe. Meeting discusses issues combat employment of atomic bombs (e.g. proper burst height, etc.). Target list is shortened to Kyoto, Hiroshima, Yokohama, and Kokura Arsenal (Niigata is considered).
General procedures for atomic bombing are completed by D.M. Dennison, under Deak Parsons.
The 100-ton test is conducted. 108 tons of TNT, laced with 1000 curies of reactor fission products, are exploded 800 yards from Trinity ground zero to test instrumentation for The Trinity Test. This is the largest instrumented explosion conducted up to this date. Also, Nazi Germany surrenders to the Allies.
The first Raytheon Mark II X-Unit arrives for detonation testing.
Initiator Committee (Hans Bethe, Enrico Fermi and Robert Christy) selects the most promising design for fission initiator (neutron generator) to be used in the implosion bomb. The "Urchin" design is favored, and work on initiator fabrication begins. Also, first batch of supplies for the atomic bomb deployment leaves for Tinian Island from Wendover, Utah.