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 Upshot-Knothole 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.

Nuclear tests

Annie

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

Nancy

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

Simon

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

Harry

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

Encore

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

File:UpshotKnothole.webm|Operation Upshot-Knothole (1953) AEC preliminary test film report.

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List of tests

{| class="wikitable sortable"

|+ United States' Upshot-Knothole series tests and detonations

|- style="vertical-align: top;"

!style="background:#ffdead;" | Name

!style="background:#efefef;" | Date time (UT)

!style="background:#ffdead;" | Local time zone

!style="background:#efefef;" | Location

!style="background:#ffdead;" | Elevation + height

!style="background:#efefef;" | Delivery<br />Purpose

!style="background:#efefef;" | Device

!style="background:#ffdead;" | Yield

!style="background:#efefef;" class="unsortable" | Fallout

!style="background:#ffdead;" class="unsortable" | References

!style="background:#efefef;" class="unsortable" | Notes

|- style="vertical-align: top;"

! Annie

| 13:20:00.3

| style="text-align:center;" | PST (-8 hrs)<br /> || NTS Area 3

| style="text-align: right;" |<br />+

| tower,<br />weapons development

| TX-5HE "XR-3" Type D pit

| style="text-align:center;" |

| I-131 detected,

"Hydride I"