Nuclear weapons testing: The "Small Boy" test shot Little Feller I becomes the last atmospheric test detonation at the Nevada National Security Site.
Little Feller II and Little Feller I were code names for a set of nuclear tests undertaken by the United States at the Nevada Test Site on July 7 and 17, 1962 as part of Operation Sunbeam. They were both tests of stockpiled W54 warheads, the smallest nuclear warheads known to have been produced by the United States, used in both the Davy Crockett warhead and the Special Atomic Demolition Munition.
In Little Feller II (July 7), the warhead was suspended only three feet above the ground and had a yield equivalent to only 22 tons of TNT (92 GJ). In Little Feller I (July 17), the warhead was launched as a Davy Crockett device from a stationary 155 millimeter launcher and set to detonate between 2040 feet (6.112.2 m) above the ground around 1.7 miles (2.7 km) from the launch point, with a yield of 18 tons of TNT (75 GJ). This test was performed in conjunction with Operation Ivy Flats, a simulated military environment, and was observed by Attorney General Robert F. Kennedy and presidential adviser General Maxwell D. Taylor.
Little Feller I has the additional distinction of being the last near-ground atmospheric nuclear detonation conducted by the United States of America (the high altitude
Fishbowl tests concluded in November 1962 with a detonation at around 69,000 feet (21 km) altitude).
All further tests were conducted under ground, in accordance with the Partial Test Ban Treaty. An additional footnote is Operation Roller Coaster. Although this later series of tests involved no true nuclear detonation, they did disperse radioactive material using conventional explosives and thus may alternatively be considered the last aboveground nuclear test.
Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by different conditions, and how personnel, structures, and equipment are affected when subjected to nuclear explosions. However, nuclear testing has often been used as an indicator of scientific and military strength. Many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status through a nuclear test.
The first nuclear device was detonated as a test by the United States at the Trinity site in New Mexico on July 16, 1945, with a yield approximately equivalent to 20 kilotons of TNT. The first thermonuclear weapon technology test of an engineered device, codenamed "Ivy Mike", was tested at the Enewetak Atoll in the Marshall Islands on November 1, 1952 (local date), also by the United States. The largest nuclear weapon ever tested was the "Tsar Bomba" of the Soviet Union at Novaya Zemlya on October 30, 1961, with the largest yield ever seen, an estimated 50–58 megatons.
In 1963, three (UK, US, Soviet Union) of the then four nuclear states and many non-nuclear states signed the Limited Test Ban Treaty, pledging to refrain from testing nuclear weapons in the atmosphere, underwater, or in outer space. The treaty permitted underground nuclear testing. France continued atmospheric testing until 1974, and China continued until 1980. Neither has signed the treaty.Underground tests in the Soviet Union continued until 1990, the United Kingdom until 1991, the United States until 1992 (its last nuclear test), and both China and France until 1996. In signing the Comprehensive Nuclear-Test-Ban Treaty in 1996, these countries have pledged to discontinue all nuclear testing; the treaty has not yet entered into force because of failure to be ratified by eight countries. Non-signatories India and Pakistan last tested nuclear weapons in 1998. North Korea conducted nuclear tests in 2006, 2009, 2013, 2016, and 2017. The most recent confirmed nuclear test occurred in September 2017 in North Korea.