Operation Upshot–Knothole

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 Artillery Fired Atomic Projectile (AFAP) 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 AFAP shell was fired (GRABLE Shot), 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. One primary device (RACER) was tested in thermonuclear system mockup assemblies of TX-14, TX-16, and TX-17/TX-24, to examine and evaluate the behaviour of radiation cases and the compression of the secondary geometries by the primary's x-rays prior to full-scale testing during Castle. Following RACER's dodgy performance, the COBRA primary was used in the emergency capability ALARM CLOCK, JUGHEAD, RUNT I, RUNT II thermonuclear devices, as well as in the SHRIMP device. RACER IV (as redesigned and proof-tested in the Simon test) was employed as primary for the ZOMBIE, RAMROD and MORGENSTERN  devices.

Annie
Planned yield for Annie was 15 ktTNT, actual yield based on radiochemical analysis was 16.2 ktTNT.

Nancy
Planned yield for Nancy was 40 ktTNT, actual yield based on radiochemical analysis was 24.5 ktTNT.

Simon
Planned yield for Simon was 33 ktTNT, actual yield based on radiochemical analysis was 43.4 ktTNT.

Harry
Planned yield for Harry was 37 ktTNT, actual yield based on radiochemical analysis was 27 ktTNT.

Encore
Planned yield for Encore was 31 ktTNT, actual yield based on radiochemical analysis was 26 ktTNT.