The "Smoky" shot of Operation Plumbbob
The 43,000 foot high cloud as seen from the control point, 30
minutes after the Priscilla event
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
.
Background
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
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 about 38,000 cases of
thyroid cancer, leading to some 1,900 deaths.
No hard data is available on the long-term civilian effects of
these tests.
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 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 tests comprising Operation Plumbbob were as follows in TNT
equivalent:
References
- Original source for test information.
- Plumbbob page on the Nuclear Weapons Archive (also
refers to manhole cover issue mentioned above).
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