An illustrated guide to the Atomic Bombs
NOTES: A large number of these photos were assembled from the RG-77-BT collection
in the Still Photo collection of the National Archives II building in College Park, MD.
"Thin Man" Plutonium Gun Type Bomb Casings in 1944. In the background you can see "Fat Man" casings.
It is unknown whether they are the early Model 1222 "Fat Man" casings, which required 1,200 bolts to assemble,
or the later Model 1561 casings which were substantially easier to assemble and which were used for the production versions.
Initial Bomb Assembly and Test
Photograph of personnel checking a casing. A significant number of extra casings were shipped to Tinian and used in
various tests with "dummy" bombs which contained all the active components of a working atomic bomb, but no fissile
material to test out and prove the assembly procedures for the actual devices themselves.
Implosion Sphere for Fat Man nearly assembled and about to be placed inside it's casing.
Photograph from LANL History website showing partially shrouded Little Boy unit
designated L-1. This unit was assembled with non-nuclear components and dropped on 23
July 1945. Test was a complete success.
Little Boy unit checked up to a bank of equipment; possibly to test/charge components
within the device. Unknown whether this is a test unit or L-11; the unit dropped on Hiroshima.
Project A (Alberta) member CDR A. Francis Birch (left) numbers Little Boy Unit L-11 while
Norman Ramsey (right) watches. This is the actual unit which was dropped on Nagasaki.
Final Bomb Assembly
Fat Man devices after they were assembled, underwent a final procedure outside the Assembly
Building, where their crevices were filled with putty, and then oversprayed with sealant to
maintain the proper environment within the device during the time it would take to deliver
it to the target
In this photograph, you can see the putty being applied to the forward polar plate.
The sealant is now being applied via spray gun.
Workers have substantially completed application of the sealant. Note the writing on the
tail fin assembly and the logo on the bomb's polar plate and on the worker's coveralls.
This is a frame taken from a color movie taken of the sealant application, showing the color of the device and sealant/putty.
Once the device was virtually complete, workers began to sign their names and various exhortations onto the device.
Close up of names on tail assembly of Fat Man.