1945: Building the Bomb

1945: Building the Bomb

Timeline Image: 
Oppenheimer and Groves

1945 Feb

Uranium gun design is completed and frozen. Only planning for deployment and combat use once the U-235 is delivered is now required (although studies of an improved gun design, begun on Dec. 7 and later abandoned, are underway).

1945 Jan 20

Curtis LeMay takes command of the Twentieth Air Force in the Marianas. The fleet contains 345 aircraft, but in three months of bombing none of the nine top priority targets have been destroyed. Also, the first stage of the K-25 Plant is charged with uranium hexafluoride and begins operation.

1945 Jan 18

The Dragon experiment conducted by Otto Frisch, in which a U-235 hydride slug is dropped through a barely subcritical U-235 hydride assembly, creates the world's first assembly critical through prompt neutrons alone (prompt critical). The largest energy production for a drop is 20 megawatts for 3 milliseconds (the temperature rises 6 degrees C in that time).

1945 Jan

160 g of plutonium from the X-10 Graphite Reactor is on hand at Los Alamos, NM. The first shipment from Hanford, WA has not yet arrived.