Overpressure is the pressure caused by a shock wave over and above normal atmospheric pressure. The shock wave may be caused by sonic boom or by explosion, and the resulting overpressure receives particular attention when measuring the effects of nuclear weapons or thermobaric bombs.
Operation Ivy was the eighth series of American nuclear tests, coming after Tumbler-Snapper and before Upshot–Knothole. The two explosions were staged in late 1952 at Enewetak Atoll in the Pacific Proving Ground in the Marshall Islands.
The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories:
Operation Crosstie was a series of 48 nuclear tests conducted by the United States in 1967–1968 at the Nevada Test Site. These tests followed the Operation Latchkey series and preceded the Operation Bowline series.
Operation Castle was a United States series of high-yield (high-energy) nuclear tests by Joint Task Force 7 (JTF-7) at Bikini Atoll beginning in March 1954. It followed Operation Upshot–Knothole and preceded Operation Teapot.
Operation Ranger was the fourth American nuclear test series. It was conducted in 1951 and was the first series to be carried out at the Nevada Test Site. All the bombs were dropped by B-50D bombers and exploded in the open air over Frenchman Flat (Area 5).
"Duck and cover" is a method of personal protection against the effects of a nuclear explosion. Ducking and covering is useful in offering a degree of protection to personnel located outside the radius of the nuclear fireball but still within sufficient range of the nuclear explosion that standing upright and uncovered is likely to cause serious injury or death. In the most literal interpretation, the focus of the maneuver is primarily on protective actions one can take during the first few crucial seconds-to-minutes after the event, while the film of the same name and a full encompassing of the advice also cater to providing protection up to weeks after the event.
Operation Wigwam involved a single test of the Mark 90 "Betty" nuclear bomb. It was conducted between Operation Teapot and Project 56 on May 14, 1955, about 500 miles (800 km) southwest of San Diego, California. 6,800 personnel aboard 30 ships were involved in Wigwam. The purpose of Wigwam was to determine the vulnerability of submarines to deeply detonated nuclear weapons, and to evaluate the feasibility of using such weapons in a combat situation. The task force commander, Admiral John Sylvester, was embarked on the task force flagship USS Mount McKinley. Wigwam was the first atomic test in the deep ocean, and it remains the only test that has been conducted in water deeper than 1,000 ft (300 m).
Operation Buster–Jangle was a series of seven nuclear weapons tests conducted by the United States in late 1951 at the Nevada Test Site. Buster–Jangle was the first joint test program between the DOD and Los Alamos National Laboratories. As part of Operation Buster, 6,500 troops were involved in the Operation Desert Rock I, II, and III exercises in conjunction with the tests. The last two tests, Operation Jangle, evaluated the cratering effects of low-yield nuclear devices. This series preceded Operation Tumbler–Snapper and followed Operation Greenhouse.
Operation Hardtack I was a series of 35 nuclear tests conducted by the United States from April 28 to August 18 in 1958 at the Pacific Proving Grounds. At the time of testing, the Operation Hardtack I test series included more nuclear detonations than the total of prior nuclear explosions in the Pacific Ocean. These tests followed the Project 58/58A series, which occurred from 1957 December 6 to 1958, March 14, and preceded the Operation Argus series, which took place in 1958 from August 27 to September 6.
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 by Joint Task Force 7 (JTF7). The entire operation followed Project 56 and preceded Project 57. The primary intention was to test new, second-generation thermonuclear weapons. Also tested were fission devices intended to be used as primaries for thermonuclear weapons, and small tactical weapons for air defense. Redwing demonstrated the first United States airdrop of a deliverable hydrogen bomb during test Cherokee. Because the yields for many tests at Operation Castle in 1954 were dramatically higher than predictions, Redwing was conducted using an "energy budget": There were limits to the total amount of energy released, and the amount of fission yield was also strictly controlled. Fission, primarily "fast" fission of the natural uranium tamper surrounding the fusion capsule, greatly increases the yield of thermonuclear devices, and constitutes the great majority of the fallout, as nuclear fusion is a relatively clean reaction.
Operation Sailor Hat was a series of explosives effects tests, conducted by the United States Navy Bureau of Ships under the sponsorship of the Defense Atomic Support Agency. The tests consisted of two underwater explosions at San Clemente Island, California in 1964 and three surface explosions at Kahoʻolawe, Hawaii in 1965. They were non-nuclear tests employing large quantities of conventional explosives to determine the effects of a nuclear weapon blast on naval vessels, and the first major test of this kind since Operation Crossroads in July 1946.
Operation Julin was a group of 7 nuclear tests conducted by the United States in 1991–1992. These tests followed the Operation Sculpin series, and were the last before negotiations began for the Comprehensive Test Ban Treaty.
Bomb Power Indicator, also known by the acronym BPI, was an instrument built to detect nuclear explosions and measure the peak overpressure of their blast waves. It was used at the twenty five British Royal Observer Corps (ROC) controls and nearly 1,500 ROC underground monitoring posts, across the United Kingdom during the Cold War.
Misty Picture was a test conducted on May 14, 1987 by the United States Defense Nuclear Agency involving the detonation of several thousand tons of conventional explosives to simulate the explosion of a small nuclear bomb.
Operation Distant Plain was a series of non-nuclear explosive and detonable gas tests performed on test sites in Alberta, Canada, during the course of 1966 and 1967. Their purpose was to provide airblast, cratering, and ground shock data in summer and winter conditions for testing new prototype equipment, military targets and coniferous forest blowdown, and defoliation.
Operation Dominic was a series of 31 nuclear test explosions ("shots") with a 38.1 Mt (159 PJ) total yield conducted in 1962 by the United States in the Pacific. This test series was scheduled quickly, in order to respond in kind to the Soviet resumption of testing after the tacit 1958–1961 test moratorium. Most of these shots were conducted with free fall bombs dropped from B-52 bomber aircraft. Twenty of these shots were to test new weapons designs; six to test weapons effects; and several shots to confirm the reliability of existing weapons. The Thor missile was also used to lift warheads into near-space to conduct high-altitude nuclear explosion tests; these shots were collectively called Operation Fishbowl.
Operation Snowball was a conventional explosive test to obtain information on nuclear weapon detonations run by the Defence Research Board with participation from the United Kingdom and United States. A detonation of 500 short tons (450 t) of TNT was used to study the resulting phenomena. The test was held at the Suffield Experimental Station in Alberta and was the largest ever man-made, non-accidental explosion in Canada. The test was also the first of its kind using a stacked TNT block hemisphere of such magnitude, a method repeated in six subsequent tests such as Operation Sailor Hat and Prairie Flat. The test allowed verifying predicted properties of shock and blast and determining its effect on a variety of military targets at varied distances from ground zero.
Operation Prairie Flat was a test involving the detonation of a 500-short-ton (450 t) spherical surface charge of TNT to evaluate airblast, ground shock and thermal effects of nuclear weapons.
