Operation Upshot-Knothole GRABLE, 1953

- Image ID: M2HY8F
Operation Upshot-Knothole GRABLE, 1953
Science History Images / Alamy Stock Photo
Image ID: M2HY8F
Operation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site. Detonation of the weapon occurred 19 seconds after its deployment at 8:30am PDT on May 25, 1953, in Area 5 of the Nevada Test Site. The codename Grable was chosen because it is phonetic for G, as in 'gun', since the warhead was a gun-type fission weapon. As a shell, or artillery-fired atomic projectile (AFAP), the device was the first of its kind. The test remains the only nuclear artillery shell ever actually fired in the U.S. nuclear weapons test program. The test series was notable as containing the first two shots (both fizzles) by University of California Radiation Laboratory-Livermore (now Lawrence Livermore National Laboratory), and for testing out some of the thermonuclear components that would be used for the massive thermonuclear series of Operation Castle.