Operation Plumbbob
Encyclopedia
Operation Plumbbob was a series of nuclear tests
conducted between May 28 and October 7, 1957, at the Nevada Test Site
, following Operation Redwing
, and preceding Operation Hardtack I
. It was the biggest, longest, and most controversial test series in the continental United States.
, of which only two did not produce any nuclear yield
. Twenty-one laboratories and government agencies were involved. While most Operation Plumbbob tests contributed to the development of warhead
s for intercontinental
and intermediate
range missile
s, they also tested air defense
and anti-submarine
warheads with smaller yields. They included forty-three 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 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. As shown and reported in the PBS documentary Dark Circle, the pigs survived, but with third-degree burns to 80% of their bodies. Other pigs were placed in pens behind large sheets of glass at measured distances from the hypocenter 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 accidental 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 KT 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.
(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.
. 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!" The use of a subterranean shaft and nuclear device to propel an object to escape velocity has since been termed a "thunder well".
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.
Objects can only be propelled to very high velocities by a nuclear explosion if they are located close to the burst point. Once a nuclear fireball has grown to a radius that is similar in size to the radius of a quantity of high explosive of similar yield, its energy density is about the same and very high velocities would not be produced. This radius for a 300 ton explosion is 3.5 meters.
The steel plate at the top of the shaft was over 150 m from the nuclear device, much too far for it to be propelled to extreme velocity directly by the explosion. The feature of Pascal-B that made this possible was the placement of the collimator close to the device. The mass of the collimator cylinder was at least 2 tonnes (if solid) and would have been vaporized by the explosion, turning it into a mass of superheated gas that expanded and accelerated up the shaft, turning it into a giant gun. It was the hypersonic expanding column of vaporized concrete striking the cover plate that propelled it off the shaft at high velocity.
To illustrate the physics, and estimate how fast it might have been going, consider that if the collimator absorbed a substantial part of the explosion energy (say a third of it, or 100 tons) it would have been heated to temperatures far higher than any conventional explosive (by a factor of 50 with the previous assumption).
The maximum velocity achieved by an expanding gas is determined by the equation:
u = 2c/(gamma - 1)
where u is the final velocity, c is the speed of sound in the gas, and gamma is the specific heat ratio of the gas. If we further assume that the thermodynamic properties of vaporized concrete are similar to the hot combustion gases of high explosives, then the speed of sound in the vaporized collimator would be about 7 km/sec (the square root of 50 times the value of c for an explosive combustion gases, which is 1 km/sec). For molecular gases gamma is usually in the range of 1.1 to 1.5, for explosives it is 1.25. Thus we get:
u = 2*7 km/sec / (1.25 - 1) = 56 km/sec
This is about five times Earth's 11.2 km/sec escape velocity, quite close to the figure of six times arrived at by Dr. Brownlee in his detailed computations.
But the assumption that it might have escaped from Earth is implausible (Dr. Brownlee's discretion in making a priority claim is well advised). Leaving aside whether such an extremely hypersonic unaerodynamic object could even survive passage through the lower atmosphere, it appears impossible for it to retain much of its initial velocity while passing through the atmosphere. A ground launched hypersonic projectile has the same problem with maintaining its velocity that an incoming meteor has. According to the American Meteor Society Fireball and Meteor FAQ meteors weighing less than 8 tonnes retain none of their cosmic velocity when passing through the atmosphere, they simply end up as a falling rock. Only objects weighing many times this mass retain a significant fraction of their velocity.
The fact that the projectile was not found of course is no proof of a successful space launch. The cylinder and cover plate of Pascal-A was also not found, even though no hypersonic projectile was involved. Even speeds typical of ordinary artillery shells can send an object many kilometers, beyond the area of any reasonable search effort.
Nuclear testing
Nuclear weapons tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the twentieth century, most nations that have developed nuclear weapons have tested them...
conducted between May 28 and October 7, 1957, at the Nevada Test Site
Nevada Test Site
The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...
, following Operation Redwing
Operation Redwing
Operation Redwing was a United States series of 17 nuclear test detonations from May to July 1956. They were conducted at Bikini and Enewetak atolls. The entire operation followed Operation Wigwam and preceded Operation Plumbbob. The primary intention was to test new, second-generation...
, and preceding Operation Hardtack I
Operation Hardtack I
Operation Hardtack I was a series of 35 nuclear tests conducted by the United States in 1958 in the Pacific Ocean.Operation Newsreel was a series of three high-altitude nuclear tests conducted as part of Hardtack I. The individual tests in the series were Orange, Teak and Yucca.-Test Blasts:-...
. It was the biggest, longest, and most controversial test series in the continental United States.
Background
The operation was the sixth test series and consisted of 29 explosionsEffects of nuclear explosions
The energy released from a nuclear weapon detonated in the troposphere can be divided into four basic categories:*Blast—40-50% of total energy*Thermal radiation—30-50% of total energy...
, of which only two did not produce any nuclear yield
Nuclear weapon yield
The explosive yield of a nuclear weapon is the amount of energy discharged when a nuclear weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene , either in kilotons or megatons , but sometimes also in terajoules...
. Twenty-one laboratories and government agencies were involved. While most Operation Plumbbob tests contributed to the development of warhead
Warhead
The term warhead refers to the explosive material and detonator that is delivered by a missile, rocket, or torpedo.- Etymology :During the early development of naval torpedoes, they could be equipped with an inert payload that was intended for use during training, test firing and exercises. This...
s for intercontinental
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...
and intermediate
Intermediate-range ballistic missile
An intermediate-range ballistic missile is a ballistic missile with a range of 3,000–5,500 km , between a medium-range ballistic missile and an intercontinental ballistic missile...
range missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
s, they also tested air defense
Anti-aircraft warfare
NATO defines air defence as "all measures designed to nullify or reduce the effectiveness of hostile air action." They include ground and air based weapon systems, associated sensor systems, command and control arrangements and passive measures. It may be to protect naval, ground and air forces...
and anti-submarine
Anti-submarine weapon
An anti-submarine weapon is any one of a range of devices that are intended to act against a submarine, and its crew, to destroy the vessel or to destroy or reduce its capability as a weapon of war...
warheads with smaller yields. They included forty-three military effects tests on civil and military structures, radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
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
Balloon
A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...
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 experiments on Frenchman Flat
Frenchman Flat
Frenchman Flat is a Tonopah Basin landform used as a nuclear weapons detonation site at the Nevada Test Site , some from Las Vegas, in the United States. Frenchman Flat is a dry lake, an alkaline desert depression which spans Area 5 and Area 11 within NTS...
. 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. As shown and reported in the PBS documentary Dark Circle, the pigs survived, but with third-degree burns to 80% of their bodies. Other pigs were placed in pens behind large sheets of glass at measured distances from the hypocenter to test the effects of flying debris on living targets.
Approximately 18,000 members of the U.S. Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
, Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
, Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
and Marines
United States Marine Corps
The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...
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
Nuclear warfare
Nuclear warfare, or atomic warfare, is a military conflict or political strategy in which nuclear weaponry is detonated on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage...
.
Studies were conducted of radiation contamination and fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
from a simulated accidental detonation of a weapon; and projects concerning earth motion, blast loading and neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
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 accidental 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 KT could be detected around the world by seismologists
Seismology
Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...
using ordinary seismic instruments. The Rainier test became the prototype
Prototype
A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...
for larger and more powerful underground tests.
Radiological effects
Plumbbob released 58,300 kilocuriesCurie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
(2.16 EBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
) of radioiodine (I-131) into the atmosphere. This produced total civilian radiation exposures amounting to 120 million person-rads
Rad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...
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
Thyroid cancer
Thyroid neoplasm is a neoplasm or tumor of the thyroid. It can be a benign tumor such as thyroid adenoma, or it can be a malignant neoplasm , such as papillary, follicular, medullary or anaplastic thyroid cancer. Most patients are 25 to 65 years of age when first diagnosed; women are more affected...
, 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
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
: ten cases, instead of the baseline expected four.
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. Before the test, 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 velocityEscape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
. 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!" The use of a subterranean shaft and nuclear device to propel an object to escape velocity has since been termed a "thunder well".
This incident was reputedly used as part of the technical justification for the Orion project
Project Orion (nuclear propulsion)
Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft...
for possible use of nuclear blasts for outer-space propulsion.
Objects can only be propelled to very high velocities by a nuclear explosion if they are located close to the burst point. Once a nuclear fireball has grown to a radius that is similar in size to the radius of a quantity of high explosive of similar yield, its energy density is about the same and very high velocities would not be produced. This radius for a 300 ton explosion is 3.5 meters.
The steel plate at the top of the shaft was over 150 m from the nuclear device, much too far for it to be propelled to extreme velocity directly by the explosion. The feature of Pascal-B that made this possible was the placement of the collimator close to the device. The mass of the collimator cylinder was at least 2 tonnes (if solid) and would have been vaporized by the explosion, turning it into a mass of superheated gas that expanded and accelerated up the shaft, turning it into a giant gun. It was the hypersonic expanding column of vaporized concrete striking the cover plate that propelled it off the shaft at high velocity.
To illustrate the physics, and estimate how fast it might have been going, consider that if the collimator absorbed a substantial part of the explosion energy (say a third of it, or 100 tons) it would have been heated to temperatures far higher than any conventional explosive (by a factor of 50 with the previous assumption).
The maximum velocity achieved by an expanding gas is determined by the equation:
u = 2c/(gamma - 1)
where u is the final velocity, c is the speed of sound in the gas, and gamma is the specific heat ratio of the gas. If we further assume that the thermodynamic properties of vaporized concrete are similar to the hot combustion gases of high explosives, then the speed of sound in the vaporized collimator would be about 7 km/sec (the square root of 50 times the value of c for an explosive combustion gases, which is 1 km/sec). For molecular gases gamma is usually in the range of 1.1 to 1.5, for explosives it is 1.25. Thus we get:
u = 2*7 km/sec / (1.25 - 1) = 56 km/sec
This is about five times Earth's 11.2 km/sec escape velocity, quite close to the figure of six times arrived at by Dr. Brownlee in his detailed computations.
But the assumption that it might have escaped from Earth is implausible (Dr. Brownlee's discretion in making a priority claim is well advised). Leaving aside whether such an extremely hypersonic unaerodynamic object could even survive passage through the lower atmosphere, it appears impossible for it to retain much of its initial velocity while passing through the atmosphere. A ground launched hypersonic projectile has the same problem with maintaining its velocity that an incoming meteor has. According to the American Meteor Society Fireball and Meteor FAQ meteors weighing less than 8 tonnes retain none of their cosmic velocity when passing through the atmosphere, they simply end up as a falling rock. Only objects weighing many times this mass retain a significant fraction of their velocity.
The fact that the projectile was not found of course is no proof of a successful space launch. The cylinder and cover plate of Pascal-A was also not found, even though no hypersonic projectile was involved. Even speeds typical of ordinary artillery shells can send an object many kilometers, beyond the area of any reasonable search effort.
List of test blasts
| Test Name | Date | Yield | Note | Image | |
|---|---|---|---|---|---|
| Boltzmann | Tower shot | ||||
| Franklin | Fizzled Fizzle (nuclear test) In nuclear weapons, a fizzle occurs when the testing of a nuclear bomb fails to meet its expected yield. The reason for the failure can be linked to improper bomb design, poor construction, or lack of expertise. All countries that have had a nuclear weapons testing program have experienced fizzles... |
||||
| Lassen | Balloon shot | ||||
| Wilson | Balloon shot | ||||
| Priscilla | Balloon shot | ||||
| Coulomb-A | Safety experiment | ||||
| Hood | Balloon shot, largest atmospheric test in the continental United States |  |
|||
| Diablo | Tower shot | ||||
| John | Live fire of AIR-2 Genie AIR-2 Genie The Douglas AIR-2 Genie was an unguided air-to-air rocket with a 1.5kt W25 nuclear warhead. It was deployed by the United States Air Force and Canada during the Cold War... air-to-air rocket |
||||
| Kepler | Tower shot | ||||
| Owens | Balloon shot | ||||
| Pascal-A | Shaft safety experiment. Yield described as slight. Expected yield was 1–2 pounds. | ||||
| Stokes | Balloon |  |
|||
| Saturn | Shaft safety experiment | ||||
| Shasta | Tower shot | ||||
| Doppler | Balloon shot | ||||
| Pascal-B | Shaft safety experiment. Yield often described as slight. Expected yield was 1–2 pounds. | ||||
| Franklin Prime | Balloon | ||||
| Smoky | Tower shot |  |
|||
| Galileo | Tower shot | ||||
| Wheeler | Balloon shot | ||||
| Coulomb-B | Surface safety experiment | ||||
| Laplace | Balloon shot | ||||
| Fizeau | Tower shot |  |
|||
| Newton | Balloon shot | ||||
| Rainier | Tunnel shot. First US underground nuclear test. | ||||
| Whitney | Tower shot |  |
|||
| Charleston | Balloon shot | ||||
| Morgan | Balloon Shot |