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Tsar Bomba (Russian: Царь-бомба, literally "Tsar Bomb"), developed by the Soviet Union, is the largest nuclear explosive ever detonated, and is also the highest power device ever used by humans. It was tested on October 30, 1961 over the island of Novaya Zemlya in the Arctic Sea. Most sources indicate that only one such weapon was ever produced.
Design
The Tsar Bomba, nicknamed "Ivan" during its development, was a multi-stage hydrogen bomb with a yield of about 50 megatonnes. (The original US estimate was 57 megatons, but since 1991 all Russian sources have stated its yield as "only" 50 megatons .) The components of the Tsar Bomba were designed by a team of physicists headed by Academician Igor Kurchatov and included Andrei Sakharov, Victor Adamsky, Yuri Babayev, Yuri Smirnov, and Yuri Trutnev. Shortly after the Tsar Bomba was detonated, Sakharov began speaking out against nuclear weapons, which culminated in his becoming a full-blown Soviet dissident (see his Memoirs).
The Tsar Bomba was not intended for use in warfare. Rather, its development and test should be seen as part of the sabre-rattling between the Soviet Union and United States in the course of the Cold War. The name was coined by analogy with Tsar Kolokol, an extraordinarily large bell and Tsar Cannon, an extraordinarily large howitzer. Like the Tsar Bomba, these were intended as demonstrations of technical prowess rather than for practical use.
Soviet Premier Nikita Khrushchev initiated the project on July 10, 1961. Design and construction took only 14 weeks, because the nuclear parts were all off-the-shelf components. The bomb weighed 27 tonnes and was 8 metres long by 2 metres in diameter. The size was such that the Tu-95 from which it was dropped had to have its bomb bay doors removed. The Tsar Bomba was attached to a special parachute weighing 800 kg, to retard its fall sufficiently to prevent the test from becoming a suicide mission. A possibly apocryphal story has it that the fabrication of this parachute required so much raw nylon that the negligible Soviet nylon hosiery industry was noticeably disrupted.
The design was capable of approximately 100 Mt, but at a cost of much radioactive fallout. (In his speeches, Khrushchev gave its yield as 100 Mt.) Any fallout from the Novaya Zemlya test would most likely have fallen on Soviet territory. To limit this fallout, the bomb was modified by replacing the uranium fusion tamper (which greatly amplifies the reaction) with one made of lead, which eliminates fast fission by the fusion neutrons. This limited the yield to 50 Mt, but resulted in a "clean" test, with approximately 97% of the energy coming from fusion rather than fission. Most of the fallout from a thermonuclear detonation results from the fission trigger, not the fusion component.
Detonation
The Tsar Bomba was detonated on October 30, 1961 at 11:33 a.m., over the nuclear testing range at Novaya Zemlya Island in the Arctic Sea. The date was chosen to overlap with the 22nd Congress of the CPSU. The bomb was carried by a specially modified Tu-95, flown by Major Andrei E. Durnotsev, and taking off from an airfield in the Kola peninsula. The bomb was dropped from an altitude of 10,500 metres, and detonated at a height of 4,000 metres over the land surface (4,200 over the sea level) by barometric sensors. The fireball touched the ground and reached nearly as high as the altitude of the release plane, which was already about 45 km distant from ground zero. The detonation was seen 1,000 km away; the subsequent mushroom cloud was about 60 km high and 30-40 km wide. The test released enough heat to cause third degree burns at a distance of 100 km, and atmospheric focusing caused blast damage up to 1,000 km away, shattering windows in Finland. The seismic shock of the test went around the Earth three times.
The Tsar Bomba was not a practical weapon, because its weight and size limited the range and speed of the specially modified bomber carrying it. A bomb of this magnitude has tremendous "blowback" potential to its user, and is inefficient by virtue of radiating much of its energy upwards into space. Contemporary nuclear weapon design employs multiple smaller warheads to produce more damage on the ground (for example, using MIRVs to deliver a "carpet" of warheads over a large area).
The full-strength version of the Tsar Bomba would have spread lethal radioactivity over an enormous area. It has been estimated that fission debris from a detonation of the original 100 Mt design would have amounted to about 25% of all fallout emitted since the invention of nuclear weapons. Employing the full-strength version against a European power would have seriously harmed the Warsaw Pact nations and the European part of the Soviet Union.
The Tsar Bomba is the most powerful device ever constructed by humans, and its test is the largest detonation ever. Since 50 Mt is 2.1×10 joules, the average power produced during the entire fission-fusion process, lasting around 3.9×10 seconds or 39 nanoseconds, was about 5.3×10 watts or 5.3 yottawatts. This constitutes over one percent of the power output of the Sun (383 yottawatts) over the same interval of time. In comparison, the largest weapon ever produced by the United States, the B41 nuclear bomb, had a predicted maximum yield of 25 Mt, and the largest weapon ever tested by the U.S. was only 15 Mt (Castle Bravo).