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Operation Upshot–Knothole

Operation Upshot–Knothole
Upshot-Knothole GRABLE.jpg
The Grable test, with the Atomic Annie artillery piece used to fire the warhead.
Country United States
Test site NTS Areas 5, 11, Frenchman Flat; NTS, Areas 1-4, 6-10, Yucca Flat
Period 1953
Number of tests 11
Test type free air drop, gun deployed, tower
Max. yield 61 kilotonnes of TNT (260 TJ)
Previous test series Operation Ivy
Next test series Operation Castle

Operation Upshot–Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site. It followed Operation Ivy and preceded Operation Castle.

Over 21,000 soldiers took part in the ground exercise Desert Rock V in conjunction with the Grable shot.Grable was a 280mm shell fired from the “Atomic Cannon” and was viewed by a number of high-ranking military officials.

The test series was notable as containing the first time an atomic artillery shell was fired (shot Grable), 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.