| Upshot–Knothole Encore | |
|---|---|
 The explosion, viewed from the air | |
| Information | |
| Country | United States |
| Test series | Operation Upshot–Knothole |
| Test site | Nevada Test Site, Area 5 |
| Date | May 8, 1953 |
| Test type | Atmospheric |
| Yield | 27 kt |
| Test chronology | |
Upshot–Knothole Encore was a nuclear weapons test conducted by the United States as part of Operation Upshot–Knothole. It took place on May 8, 1953 in Yucca Flat, in the Nevada Test Site. [1]
The test device, codenamed Encore, was detonated at 8:30 local time by performing an airdrop of a Mk-6D bomb from 19,000 feet (5,800 m) with a B-50 Superfortress over Area 5 at the Nevada Test Site. At 2,423 feet (739 m), the bomb detonated, although it was 15 feet (4.6 m) west and 937 feet (286 m) south of its designated target. The estimated yield of the weapon was 30-36 kilotons, although it yielded 27 kilotons. In the codename "Encore", the letter "E" was a reference to the "effects" of weapons testing. [2]
As Encore was an effects test, multiple objects were subjected to the blast, including trees. Since the Nevada Test Site sits in a desert and does not contain trees, the United States Forest Service transported 145 Ponderosa pines from a nearby canyon to Area 5. The trees were then placed in holes at Frenchman Flat, and cemented into the ground, 6,500 feet from ground zero. The initial release of thermal radiation ignited many of the trees, and the subsequent blast wave blew them over. [3] Model houses built for the test were recorded to produce the Civil Defense film The House in the Middle . [4]
Soldiers were brought in to view the blast as part of the Desert Rock exercises. [5] 3,500 soldiers from all over the country participated in the exercises, and were formed into Combat Battalion teams. In addition to this, six hundred high-ranking personnel and congressmen were on hand to view the exercises, which were aimed to "indoctrinate troops in atomic weapons in order that they will know how to protect themselves and their equipment in event of an enemy atomic attack in combat situations". [6]
The Nevada National Security Sites, popularized as the Nevada Test Site (NTS) until 2010, is a reservation of the United States Department of Energy located in the southeastern portion of Nye County, Nevada, about 65 mi (105 km) northwest of the city of Las Vegas.
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.
Project Plowshare was the overall United States program for the development of techniques to use nuclear explosives for peaceful construction purposes. The program was organized in June 1957 as part of the worldwide Atoms for Peace efforts. As part of the program, 35 nuclear warheads were detonated in 27 separate tests. A similar program was carried out in the Soviet Union under the name Nuclear Explosions for the National Economy, although the Soviet program consisted of 124 tests.
Nuclear weapons tests are experiments carried out to determine the performance of nuclear weapons and the effects of their explosion. Nuclear testing is a sensitive political issue. Governments have often performed tests to signal strength. Because of their destruction and fallout, testing has seen opposition by civilians as well as governments, with international bans having been agreed on. Thousands of tests have been performed, with most in the second half of the 20th century.
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).
Operation Upshot–Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site. It followed Operation Ivy and preceded Operation Castle.
Operation Teapot was a series of 14 nuclear test explosions conducted at the Nevada Test Site in the first half of 1955. It was preceded by Operation Castle, and followed by Operation Wigwam. Wigwam was, administratively, a part of Teapot, but it is usually treated as a class of its own. The aims of the operation were to establish military tactics for ground forces on a nuclear battlefield and to improve the nuclear weapons used for strategic delivery.
Operation Plumbbob was a series of nuclear tests that were conducted between May 28 and October 7, 1957, at the Nevada Test Site, following Project 57, and preceding Project 58/58A.
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.
Upshot–Knothole Simon was a nuclear detonation conducted as part of the U.S. Operation Upshot–Knothole nuclear testing program. Simon was conducted on 25 April 1953 at the Nevada Test Site, and tested the TX-17/24 thermonuclear weapon design which had a yield of 43 kilotons.
The W9 was an American nuclear artillery shell fired from a special 280 mm howitzer. It was produced starting in 1952 and all were retired by 1957, being superseded by the W19.
Upshot–Knothole Grable was a nuclear weapons test conducted by the United States as part of Operation Upshot–Knothole. Detonation of the nuclear weapon, a W9 warhead, occurred 19 seconds after its deployment at 8:30am PDT on May 25, 1953, in Area 5 of the Nevada Test Site.
Gerboise Bleue was the codename of the first French nuclear test. It was conducted by the Nuclear Experiments Operational Group (GOEN), a unit of the Joint Special Weapons Command on 13 February 1960, at the Saharan Military Experiments Centre near Reggane, French Algeria in the Sahara desert region of the Tanezrouft, during the Algerian War. General Pierre Marie Gallois was instrumental in the endeavour, and earned the nickname of père de la bombe A.
A fizzle occurs when the detonation of a device for creating a nuclear explosion grossly fails to meet its expected yield. The bombs still detonate, but the detonation is much weaker than anticipated. The cause(s) for the failure might be linked to improper design, poor construction, or lack of expertise. All countries that have had a nuclear weapons testing program have experienced some fizzles. A fizzle can spread radioactive material throughout the surrounding area, involve a partial fission reaction of the fissile material, or both. For practical purposes, a fizzle can still have considerable explosive yield when compared to conventional weapons.
Yucca Flat is a closed desert drainage basin, one of four major nuclear test regions within the Nevada Test Site (NTS), and is divided into nine test sections: Areas 1 through 4 and 6 through 10. Yucca Flat is located at the eastern edge of NTS, about ten miles (16 km) north of Frenchman Flat, and 65 miles (105 km) from Las Vegas, Nevada. Yucca Flat was the site for 739 nuclear tests – nearly four of every five tests carried out at the NTS.
Upshot-Knothole Dixie was the fourth test-firing of Operation Upshot–Knothole, an atomic weapons test series conducted in 1953 by the United States at the Nevada Test Site.
Upshot–Knothole Harry (UK#9) was a nuclear weapons test conducted by the United States as part of Operation Upshot–Knothole. It took place at the recorded time of 04:05 hours, on May 19, 1953, in Yucca Flat, in the Nevada Test Site. The sponsor of the test was the National Laboratory of the United States of America located at Los Alamos.
Frenchman Flat is a hydrographic basin in the Nevada National Security Site south of Yucca Flat and north of Mercury, Nevada. The flat was used as an American nuclear test site and has a 5.8 sq mi (15 km2) dry lake bed that was used as a 1950s airstrip before it was chosen after the start of the Korean War for the Nevada Proving Grounds. Nellis Air Force Base land 12 mi × 30 mi was transferred to the Atomic Energy Commission on which Site Mercury was constructed on the flat for supporting American nuclear explosive tests. The 1951 Operation Ranger "Able" test was the first continental US nuclear detonation after the 1945 Trinity test, and Frenchman Flat also had the only detonation of an American artillery-fired nuclear projectile in the 1953 Upshot-Knothole Grable test using the M65 Atomic Cannon.
Upshot–Knothole Annie was one of eleven nuclear weapons tests conducted by the United States as part of Operation Upshot–Knothole. It took place at the Nevada Test Site on 17 March 1953, and was nationally televised. The device used in the blast was a 16 kt Mark 5 Nuclear Bomb - a low yield fission weapon, detonated 90 meters / 300 feet above the ground. The live TV coverage was recorded on a kinescope, so it is a rare record of the sound an actual atomic bomb makes.
