Operation Upshot-Knothole

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The fireball from the Upshot-Knothole Grable test.

Operation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site.

Over twenty-one thousand 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.

Operation Upshot-Knothole followed Operation Ivy and preceded Operation Castle. 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.

The individual shots were:

The Grable test, including the artillery piece used to fire the warhead

Upshot-Knothole Test Blasts
Test Name	Date	Location	Yield	Note
Annie	17 March, 1953	Nevada Test Site	16 kilotons
Nancy	24 March, 1953	Nevada Test Site	24 kilotons
Ruth	31 March, 1953	Nevada Test Site	0.2 kilotons	First UCRL device, uranium hydride device, fizzle
Dixie	6 April, 1953	Nevada Test Site	11 kilotons
Ray	11 April, 1953	Nevada Test Site	0.2 kilotons	Second UCRL device, uranium hydride device, fizzle
Badger	18 April, 1953	Nevada Test Site	23 kilotons
Simon	25 April, 1953	Nevada Test Site	43 kilotons
Encore	8 May, 1953	Nevada Test Site	27 kilotons
Harry	19 May, 1953	Nevada Test Site	32 kilotons	Extreme contamination of downwinders
Grable	25 May, 1953	Nevada Test Site	15 kilotons	nuclear artillery, gun-type fission weapon
Climax	4 June, 1953	Nevada Test Site	61 kilotons