NUCLEAR WEAPONSLittle Boy Postwar History Mystery

By Jim Danneskiold

Published 22 August 2024

Early on in the summer of 1945, weaponeers at Los Alamos National Laboratory were extremely dismissive of Little Boy, seeing the uranium gun-type bomb as a hedge against possible failure of the program to build the more complex Fat Man plutonium bomb, and a potential tool for future specialized missions.

Historian Alex Wellerstein offered fascinating insights into the intricacies of his research into the early days of nuclear weapons in his talk, “Little Boy After Hiroshima,” the second in the Sandia National Laboratories’  75th Anniversary Speaker Series.

Wellerstein, a professor at the Stevens Institute of Technology in New Jersey, spokelast week to an audience of about 500 Sandians at the Steve Schiff Auditorium and online.

His interest began with the big question of how the U.S. nuclear weapons stockpile evolved. While researching the immediate postwar period for a book on nuclear policymaking in the Truman administrations, he became fascinated with trying to find out how many Little Boy-type fission weapons the U.S. produced besides the one dropped in Hiroshima in August 1945.

Early on, he said, weaponeers at Los Alamos National Laboratory were extremely dismissive of Little Boy, seeing the uranium gun-type bomb as a hedge against possible failure of the program to build the more complex Fat Man plutonium bomb, and a potential tool for future specialized missions. By late 1945, they considered it definitely “obsolete,” as it required much more fissile material to achieve an even lower explosive yield than Fat Man.

By spring 1946, however, documents showed a change: “Little Boy is apparently desired in the stockpile,” due to plutonium production issues at Hanford, Wellerstein said. Later that year, the Navy made clear its interest in deploying it on aircraft carriers.

Often overlooked was Sandia’s role in those early days, he said, principally focused on moving weapon designs and developments such as the postwar Little Boy through the engineering phase and onto “The Road” to military deployment.

Scouring a range of declassified documents and linking them to highly enriched uranium production reports and a variety of other early government charts, Wellerstein wove a picture of what this “retrogression” in the early stockpile tells us about the complex and uncertain postwar period, and how the modern nuclear weapons complex evolved.

He concluded that obsolescence for Little Boy was a matter of context. Though less efficient than Fat Man, circumstances led different groups to determine it was desirable to add a small number of Little Boys to the postwar stockpile.

How many were added remains somewhat inconclusive due to conflicts in the many sources and documents, though the early stockpile included components of a couple of dozen Little Boys. Wellerstein said that it appears that as many as 10 weapons may have been available by 1950, but that even that number was dependent on uncertain definitions.

“What do we mean by a Little Boy bomb?” he asked. “What do we even mean by the stockpile? We have a little bit of this and a little bit of that.”

Jim Danneskiold is Manager, Media Relations at Sandia National Laboratories. The article was originally posted to the website of Sandia National Laboratories.