Atomic Bomb Design Morris Jeppson Hand-Annotated “Little Boy” Diagram from the Hiroshima Mission, 1945

Morris Jeppson

Manuscript & Autographs

Jeppson, Morris. Hand-annotated diagram of the “Little Boy” atomic bomb, 1945, provides a direct technical interpretation of the weapon used in the bombing of Hiroshima by a participant who bridged both its development and deployment. As weapons officer aboard the Enola Gay and a scientist present at Los Alamos Laboratory, Jeppson occupied a rare dual role linking the Manhattan Project’s design phase with the operational execution of nuclear warfare. His annotations explain the internal structure and function of the uranium gun-type bomb, offering a contemporaneous explanation of how critical mass was achieved and how the weapon was triggered. The document situates technical knowledge of nuclear fission within the lived experience of those responsible for its first use in warfare during World War II.

Jeppson, Morris. “Little Boy” atomic bomb diagram. United States, 1945. One-page black-and-white printed diagram with extensive handwritten annotations and arrows in ink, signed at lower margin “Morris Jeppson / Weapon Test Officer / Enola Gay Mission / HIROSHIMA 6 Aug. 1945.” The annotations identify and explain key components, including “target U235,” “projectile 235,” and the process by which the bomb “Becomes critical mass with projectile,” along with labeled elements such as the “electric detonator,” “gun barrel,” and “one of 4 radar antennas.” The markings function as a technical overlay to the printed schematic, clarifying both structure and mechanism from the perspective of the officer responsible for in-flight arming and monitoring of the device.

The atomic bombing of Hiroshima marked the first combat use of nuclear weapons and introduced a new phase of warfare defined by unprecedented destructive capacity and strategic implications. Jeppson’s role in both the scientific and operational dimensions of the mission positions this document within the immediate transmission of specialized knowledge from laboratory to battlefield. His annotations provide insight into how participants understood and communicated the bomb’s function, contributing to the historical record of nuclear science, military technology, and the transformation of warfare at the end of World War II.

Light handling wear; diagram remains clear with strong, legible annotations and signature. Overall very good.

Item #12577

Price: $550.00