The operation was the sixth test series and consisted of 29 explosions, of which two did not produce any nuclear yield. 21 laboratories and government agencies were involved. While most Operation Plumbbob tests contributed to the development of warheads for intercontinental and intermediate range missiles, they also tested air defense and anti-submarine warheads with small yields. They included 43 military effects tests on civil and military structures, radiation and bio-medical studies, and aircraft structural tests. Operation Plumbbob had the tallest tower tests to date in the U.S. nuclear testing program, as well as high-altitude balloon tests. One nuclear test involved the largest troop maneuver ever associated with U.S. nuclear testing.

Almost 1,200 pigs were subjected to bio-medical experiments and blast-effects studies during Operation Plumbbob. On shot Priscilla (37 KT), 719 pigs were used in various different experiments on Frenchman Flat. Some pigs were placed in elevated cages and provided with suits made of different materials, to test which materials provided best protection from the thermal pulse. Other pigs were placed in pens at measuring distances from the epicenter behind large sheets of glass to test the effects of flying debris on living targets.

Approximately 18,000 members of the U.S. Air Force, Army, Navy and Marines participated in exercises Desert Rock VII and VIII during Operation Plumbbob. The military was interested in knowing how the average foot-soldier would stand up, physically and psychologically, to the rigors of the tactical nuclear battlefield.

Studies were conducted of radiation contamination and fallout from a simulated accidental detonation of a weapon; and projects concerning earth motion, blast loading and neutron output were carried out.

Nuclear weapons safety experiments were conducted to study the possibility of a nuclear weapon detonation during an accident. On July 26, 1957, a safety experiment, "Pascal-A" was detonated in an unstemmed hole at NTS, becoming the first underground shaft nuclear test. The knowledge gained here would provide data to prevent nuclear yields in case of accidential detonations, for example a plane crash.

The Rainier shot, conducted September 19, 1957, was the first fully contained underground nuclear test, meaning that no fission products were vented into the atmosphere. This test of 1.7 kilotons could be detected around the world by seismologists using ordinary seismic instruments. The Rainier test became the prototype for larger and more powerful underground tests.

Radiological effects

The 43,000 foot high cloud as seen from the control point, 30 minutes after the Priscilla event

Plumbbob released 58,300 kilocuries (2.16 EBq) of radioiodine (I-131) into the atmosphere. This produced total civilian radiation exposures amounting to 120 million person-rads of thyroid tissue exposure (about 32% of all exposure due to continental nuclear tests).

Statistically speaking, this level of exposure would be expected to eventually cause between 11,000 and 212,000 excess cases of thyroid cancer, leading to between 1,000 and 20,000 deaths.

In addition to civilian exposure, troop exercises conducted near the ground near shot "Smoky" exposed over three thousand servicemen to relatively high levels of radiation. A survey of these servicemen in 1980 found significantly elevated rates of leukemia: ten cases, instead of the baseline expected four.[citation needed]

Hood's radioactive cloud tops off at nearly 49,000 feet above Yucca flats, as seen from 14 miles away. The detonation sent an above normal thermal pulse across the desert, igniting bushes and other growth up to 3 miles away on nearby foothills, as seen to the right of the dust cloud on the desert floor

The first nuclear-propelled manmade object in space?

During the Pascal-B nuclear test, a heavy (900 kg) steel plate cap (a piece of armor plate) was blasted off the top of a test shaft at an unknown speed. The test's experimental designer Dr. Brownlee had performed a highly approximate calculation that suggested that the nuclear explosion, combined with the specific design of the shaft, would accelerate the plate to six times escape velocity. The plate was never found, but Dr. Brownlee believes that the plate never left the atmosphere (it may even have been vaporized by compression heating of the atmosphere due to its high speed). The calculated velocity was sufficiently interesting that the crew trained a high-speed camera on the plate, which unfortunately only appeared in one frame, but this nevertheless gave a very high lower bound for the speed. After the event, Dr. Robert R. Brownlee described the best estimate of the cover's speed from the photographic evidence as "going like a bat!!"

This incident was reputedly used as part of the technical justification for the Orion project for possible use of nuclear blasts for outer-space propulsion.

List of tests

The tail, or ft, section of a U.S. Navy Blimp is shown with the Stokes cloud in background. The blimp was over five miles from ground zero when it was collapsed by the shock wave. The airship was unmanned and was used in military effects experiments on blast and heat. Navy personnel on the ground in the vicinity of the experimental area were unhurt. On the ground to the left are the remains of the blimp's forward section.

The fireball from the 74 kiloton "Hood" thermonuclear event as seen from the control point 14 miles from ground zero. Hood was the largest atmospheric nuclear event to occur on the continent. The blast was powerful enough to rattle windows over 300 miles away in California, and the flash was seen by an airline pilot flying over Hawaii, about 2700 miles from the NTS.

The tests comprising Operation Plumbbob were as follows in TNT equivalent:

Operation Plumbbob Test Blasts

Test Name






12 kt

Tower shot



140 tons



5 June 1957

0.5 kt

Balloon shot


18 June 1957

10 kt

Balloon shot


24 June 1957

37 kt

Balloon shot


1 July 1957

zero yield

Safety experiment


5 July 1957

74 kt

Balloon shot, largest atmospheric test in the continental United States


15 July 1957

17 kt

Tower shot


19 July 1957

2 kt

Live fire of AIR-2 Genie air-to-air rocket


24 July 1957

10 kt

Tower shot


25 July 1957

9.7 kt

Balloon shot


26 July 1957


Shaft safety experiment


7 August 1957

19 kt



10 August 1957

Zero yield

Shaft safety experiment


18 August 1957

17 kt

Tower shot


23 August 1957

11 kt

Balloon shot


27 August 1957


Shaft safety experiment

Franklin Prime

30 August 1957

4.7 kt



31 August 1957

44 kt

Tower shot


2 September 1957

11 kt

Tower shot


6 September 1957

197 tons

Balloon shot


6 September 1957

300 tons

Surface safety experiment


8 September 1957

1 kt

Balloon shot


14 September 1957

11 kt

Tower shot


16 September 1957

12 kt

Balloon shot


19 September 1957

1.7 kt

Tunnel shot. First US underground nuclear test.


23 September 1957

19 kt

Tower shot


28 September 1957

12 kt

Balloon shot


7 October 1957

8 kt

Balloon Shot


"United States Nuclear Tests, July 1945 through September 1992 (DOE/NV-209)" (pdf). U.S. Department of Energy Nevada Operations Office. 2000.  Original source for test information.

Plumbbob page on the Nuclear Weapons Archive (also refers to manhole cover issue mentioned above).

"Estimated Exposures and Thyroid Doses Received by the American People from Iodine-131 in Fallout Following Nevada Atmospheric Nuclear Bomb Tests". National Cancer Institute. 1997. 


Wikimedia Commons has media related to: Operation Plumbbob

^ Institute of Medicine (U.S.). Committee on Thyroid Screening Related to I-131 Exposure, National Research Council (U.S.). Committee on Exposure of the American People to I-131 from the Nevada Atomic Bomb Tests, ed (1999) (in English). Exposure of the American people to Iodine-131 from Nevada nuclear-bomb tests: review of the National Cancer Institute report and public health implications. National Academies Press. pp. 113-114. ISBN 9780309061759.;="operation+plumbbob"+OR+nevada+atmospheric+"thyroid+cancer"&ei=zN98S8TAEqTgkQTGwfz-CA&client=firefox-a&cd=2#v=onepage&q="operation plumbbob" OR nevada atmospheric "thyroid cancer"&f=false. 

^ Brownlee, Robert R. (June 2002). "Learning to Contain Underground Nuclear Explosions". Retrieved 2006-07-31. 

^ Learning to Contain Underground Nuclear Explosions By Dr. Robert R. Brownlee - June 2002

^ Operation Plumbob at the Nuclear Weapon Archive

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