http://en.wikipedia.org/wiki/Tsar_Bomba
Tsar Bomba
Tsar Bomba, literally "Tsar-bomb", is the nickname for the AN602 hydrogen bomb (codenamed "Ivan"[citation needed] by its developers) — the largest, most powerful nuclear weapon ever detonated, and currently the most powerful explosive ever detonated in human history.
Developed by the Soviet Union, the bomb was originally designed to have a yield of about 100 megatons of TNT (420 PJ); however, the bomb yield was reduced by half in order to limit the amount of nuclear fallout that would result. One bomb was built and tested on October 30, 1961, in the Novaya Zemlya archipelago. The weapon never entered service.
A mock bomb was stored in the Russian Nuclear Weapons Museum in Sarov.
The Tsar Bomba was a three-stage hydrogen bomb with a yield of 57 megatons (Mt). This is equivalent to ten times the amount of all the explosives used in World War II combined, including Little Boy and Fat Man, the bombs that destroyed Hiroshima and Nagasaki. A three-stage H-bomb uses a fission bomb primary to compress a thermonuclear secondary, as in most H-bombs, and then uses energy from the resulting explosion to compress a much larger additional thermonuclear stage. However, there is evidence that the Tsar Bomba had a number of third stages rather than a single very large one.
The initial three-stage design was capable of approximately 100 Mt, but at a cost of too much radioactive fallout. To limit fallout, the third stage, and possibly the second stage, had a lead tamper instead of a uranium-238 fusion tamper (which greatly amplifies the reaction by fissioning uranium atoms with fast neutrons from the fusion reaction). This eliminated fast fission by the fusion-stage neutrons, so that approximately 97% of the total energy resulted from fusion alone (as such, it was one of the "cleanest" nuclear bombs ever created, generating a very low amount of fallout relative to its yield). There was a strong incentive for this modification since most of the fallout from a test of the bomb would fall on populated Soviet territory.
The Tsar Bomba was flown to its test site by a specially modified Tu-95V release plane, flown by Major Andrei Durnovtsev, which took off from an airfield in the Kola peninsula. The release plane was accompanied by a Tu-16 observer plane that took air samples and filmed the test. Both aircraft were painted with a special reflective white paint to limit heat damage.
The bomb, weighing 27 tons, was so large (8 metres (26 ft) long by 2 metres (6.6 ft) in diameter) that the Tu-95V had to have its bomb bay doors and fuselage fuel tanks removed. The bomb was attached to an 800 kilogram fall-retardation parachute, which gave the release and observer planes time to fly about 45 kilometres (28 mi) from ground zero.
The Tsar Bomba detonated at 11:32 on October 30, 1961 over the Mityushikha Bay nuclear testing range (Sukhoy Nos Zone C), north of the Arctic Circle on Novaya Zemlya Island in the Arctic Sea. The bomb was dropped from an altitude of 10.5 kilometres (6.5 mi); it was designed to detonate at a height of 4 kilometres (2.5 mi) over the land surface (4.2 kilometres (2.6 mi) over sea level) by barometric sensors.
The original U.S. estimate of the yield was 57 Mt, but since 1991 all Russian sources have stated its yield as 50 Mt. Khrushchev warned in a filmed speech to the Communist parliament of the existence of a 100 Mt bomb (technically the design was capable of this yield). The fireball touched the ground, reached nearly as high as the altitude of the release plane, and was seen and felt almost 1,000 kilometres (620 mi) from ground zero. The heat from the explosion could have caused third degree burns 100 km (62 miles) away from ground zero. The subsequent mushroom cloud was about 64 kilometres (40 mi) high (nearly seven times higher than Mount Everest) and 40 kilometres (25 mi) wide. The explosion could be seen and felt in Finland, breaking windows there and in Sweden. Atmospheric focusing caused blast damage up to 1,000 kilometres (620 mi) away. The seismic shock created by the detonation was measurable even on its third passage around the Earth. Its Richter magnitude was about 5 to 5.25. The energy yield was around 7.1 on the Richter scale, but since the bomb was detonated in air rather than underground, most of the energy was not converted to seismic waves.
Since 50 Mt is 2.1×1017 joules, the average power produced during the entire fission-fusion process, lasting around 39 nanoseconds, was about 5.4×1024 watts or 5.4 yottawatts (5.4 septillion watts). This is equivalent to approximately 1.4% of the power output of the Sun.
The Tsar Bomba is the single most physically powerful device ever utilized throughout the history of humanity. Its size and weight excluded a successful delivery in case of a real war.
http://dictionary.reference.com/browse/underground
underground
existing, situated, operating, or taking place beneath the surface of the ground.
the place or region beneath the surface of the ground.
Situated, occurring, or operating below the surface of the earth: underground caverns; underground missile sites.
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