spectacular Manhattan Project relic

This evocative relic of the first atomic bomb was preserved by the first metallurgist of the Manhattan Project’s Metallurgical Laboratory, Jules Simmons.

This aluminum hemisphere was part of an early mock-up illustrating the concept of the plutonium implosion device ultimately used in the Trinity and Nagasaki blasts. In the planned implosion bomb, the center cavity would hold a plutonium core, surrounded by a sphere of depleted uranium.

Of particular note is the machined step, which aligned the hemispheres and created a non-linear joint between the hemispheres. This was important because the core would be imploded by about 5000 pounds of Composition B high explosive. The interrupted joint reduced the phenomenon of explosive jetting. Under the pressures generated by the implosion a simple joint would allow non-symmetrical jetting by the shock wave to reach the core and disrupt the spherical geometry and cause a fizzle (no or low nuclear yield). The threaded post at the center allowed the hemispheres to be joined by a threaded rod for purposes of illustration.

This hemisphere was evidently made prior to the completion of Los Alamos experiments to determine the final weapon component engineering and dimensions. Ultimately the plutonium pit was approximately 3.5 inches in diameter and the depleted uranium tamper was approximately 8 inches in diameter. These proportions roughly correspond to the size of the present preliminary mock-up.

It is likely that this hemisphere and its mate were used in scientific meetings within the Manhattan Project to illustrate the implosion concept used in Trinity and at Nagasaki.

Provenance: Jules Simmons (1907-87), first metallurgist at the Manhattan Project’s Metallurgical Laboratory, University of Chicago. Accompanying documents include:

A family provenance letter stating that Simmons took home this piece, the third attempt of five, because of its imperfections.

Simmons, “History of Uranium Fabrication and Development of Fuel Elements for CO-43,” an 18-page memoir of the Manhattan Project Metallurgical Laboratory.

A letter from Ed Creutz, the Manhattan Project group leader who hired Simmons, calling him “certainly one of the important technical leaders of the Manhattan Project” and “the first real metallurgist on the metallurgical project working with me.”

Manhattan District certificate from Secretary of War Henry Stimson for Simmons’s contributions to the atomic bomb effort, dated August 6, 1945.

and many more

$11,000