Yucca Flat

August 31, 1957 – Plumbbob’s “Smoky” Leaves a Troubled Legacy

On August 31, 1957, Operation Plumbob’s “Smoky” test flamed into the sky over busy Yucca Flat, 65 miles north of Las Vegas.  Area 8 of the Nevada Test Site played host that day to the third test of the UCRL TX-41 –  a three-stage, thermonuclear weapon design.  After two previous tests of 3.5 and 5.0 megatons (Redwing Zuni and Tewa), “Smoky” was probably a partial, two-stage test with a decreased yield of 45-50 kilotons.  The MK-41 nuclear device eventually developed from the TX-41 test series became the largest-yield nuclear weapon ever developed or deployed by the United States.  Its yield of 25 megatons was also the highest yield-to-weight ratio for a US nuclear weapon, at about 6 kilotons per kilogram.

Smoky became famous – notorious, even – for its tragic consequences.   Over three thousand servicemen had been in the vicinity of ground zero shortly after the blast, practicing maneuvers as part of the Desert Rock exercise.  Their exposure to radiation from the test eventually became the subject of a Congressional investigation and epidemiological evaluation.  A 1980 study found statistically significant increases in leukemia cases among the 3224 participants.  Instead of the expected four cases, ten were found.

August 27, 1957 – Underground Nuclear Test Launches Giant “Manhole Cover”

On August 27, 1957, a four-inch-thick steel plate weighing several hundred pounds shot into the stratosphere over the Nevada Test Site, never to be seen again.  Operation Plumbbob’s Pascal-B was an underground test of a nuclear safety device designed to limit the amount of destructive energy released by a bomb in the event of an accidental detonation.  Buried at the bottom of a 500-foot shaft and sealed with an over-2-ton plug of cement, Pascal-B generated sufficient energy – the equivalent of a few hundred tons of dynamite – to vaporize the concrete plug.  The concrete vapor expanded and raced up the shaft, propelling a massive steel plate sealing the shaft opening into the sky.

According to the February 1992 issue of the Smithsonian’s Air and Space Magazine, astrophysicist Bob Brownlee was in charge of designing the Pascal-B test.  “He knew the lid [steel plate] would be blown off; he didn’t know exactly how fast.  High-speed cameras caught the giant manhole cover as it began its unscheduled flight into history.  Based on his calculations and the evidence from the cameras, Brownlee estimated that the steel plate was traveling at a velocity six times that needed to escape Earth’s gravity when it soared into the flawless blue Nevada sky.  ‘We never found it.  It was gone,’ Brownlee says, a touch of awe in his voice almost 35 years later”.

Even though the eventual whereabouts of the steel plate forever remained a mystery, it’s unlikely, according to the laws of physics and the character of the Earth’s atmosphere, that the plate headed into outer space.  Unable to maintain escape velocity on its own (not being equipped with mini-rocket engines), it would not retain sufficient speed to pass completely through the layers of nitrogen, oxygen, and other gases surrounding our planet.  Most likely it either vaporized in the explosion, disintegrated in the atmosphere, or landed somewhere far from the Nevada Test Site.  It’s also possible it became some innocent person’s “close encounter”, or enormous fish story.

July 19, 1957 – First Genie Nuclear Rocket Test at Yucca Flat

John Operation Plumbbob

On July 19, 1957, the Nevada Testing Site (NTS) hosted the first test-firing of the AIR-2 Genie air-to-air rocket.  Part of Operation Plumbbob, the “John” test over Yucca Flat involved the successful launch and detonation of the nuclear-warhead-tipped rocket from a Northrup F-89J fighter without demolishing the aircraft itself.  The AIR-2 Genie was designed to destroy incoming enemy bombers with its 1.7-kiloton, plutonium core Genie W-25 warhead.  The rocket traveled 4240 meters in 4.2 seconds, achieving about Mach 3, before detonating approximately three miles over five volunteers and a photographer at ground zero in Yucca Flat’s Area 10.  Their presence at the test site was intended to show the apparent safety of battlefield nuclear weapons to personnel on the ground.

Image Credit: U.S. Air Force

July 5, 1957 – Largest US Continental Atmospheric Nuclear Test Over Yucca Flat

Operation Plumbbob DOE

Operation Plumbbob

On July 5, 1957, the “Hood” test of Operation Plumbbob took place over Area 9 of Yucca Flat, a closed desert drainage basin within the Nevada Test Site (NTS) sixty-five miles northwest of Las Vegas.  Referred to as “the most irradiated, nuclear-blasted spot on the face of the earth”, Yucca Flat was the testing ground – both in the air and under the surface of the flat, sandy soil – for 739 nuclear tests from October of 1951 to September of 1992, when a moratorium temporarily halted all nuclear testing.

The Hood test involved the atmospheric detonation of a 74-kiloton bomb which had been carried by balloon to an elevation of 460 meters.  Two thousand American troops were on hand for training in nuclear battlefield operations.  Eleven million Curies of radioactive Iodine-131 were released by the bomb as a determinant used to track specific nuclear contamination events.  The bomb detonated in the Hood test was nearly five times larger than the bomb dropped on Hiroshima.

NTS has been studied extensively to evaluate the nuclear contamination of its soil and groundwater.  In his book, Aftermath: The Remnants of War, author Webster Donovan states that NTS has been characterized as a “national sacrifice zone”, due to the great expense and virtual impossibility of cleaning up the site.

Image Credit: US Department of Energy/flickr