Tsar Bomba (1961): The Largest Nuclear Weapon Ever Detonated

Tsar Bomba was a Soviet hydrogen bomb detonated over the Arctic archipelago of Novaya Zemlya on 30 October 1961. With an estimated yield of around 50 megatons, it remains the most powerful nuclear explosion ever carried out. Ordered by Nikita Khrushchev at the height of the Berlin crisis, it was less a practical weapon than a demonstration of Soviet power, and it became a symbol of how far the nuclear arms race had gone.

Background: the arms race in 1961

The Soviet Union tested its first atomic bomb in 1949 and its first true two-stage thermonuclear device in November 1955. The United States had tested much larger hydrogen bombs, including the 15-megaton Castle Bravo shot in 1954. A megaton is the energy released by one million tonnes of TNT.

In 1958 the United States, Britain and the Soviet Union began an informal moratorium on nuclear testing while they negotiated a ban. By 1961 relations had deteriorated sharply. The U-2 spy plane affair of 1960, the failed Vienna summit in June 1961 and the construction of the Berlin Wall in August raised tensions to a dangerous level.

On 31 August 1961 the Soviet government announced that it would resume testing, and a new series began on 1 September. Khrushchev wanted to show strength and to counter American superiority in long-range delivery systems. A super-large bomb offered a dramatic way to do so.

Khrushchev had a taste for blunt threats. At the United Nations in 1960 he had used a Russian idiom promising to show the West “Kuzka’s mother”, roughly meaning to teach someone a harsh lesson. Within the Soviet weapons programme the new giant bomb was informally nicknamed after that phrase. The decision to build it was taken only in July 1961, about four months before the test, and the designers worked under intense political pressure to have it ready in time for the Party Congress in October.

Design and development

The weapon was developed at the secret design bureau known as Arzamas-16 (today Sarov), under scientific director Yuli Khariton. A team that included Andrei Sakharov, Viktor Adamsky, Yuri Babayev, Yuri Smirnov and Yuri Trutnev produced the design in a remarkably short time during the summer and autumn of 1961. Its official designation was usually given as RDS-220 or AN602; the name “Tsar Bomba” (“Tsar of bombs”) was coined later, by analogy with the Tsar Cannon and Tsar Bell in the Moscow Kremlin, and Western writers also called it “Big Ivan”.

The device used a three-stage design. A fission primary triggered a thermonuclear secondary, which in turn ignited a larger tertiary stage. In its full configuration, with uranium-238 tampers, the design could have produced about 100 megatons. That version, however, would have created enormous radioactive fallout, much of it over Soviet territory.

To reduce the danger, the designers replaced the uranium in the outer stages with lead. This roughly halved the yield and meant that around 97 percent of the energy came from fusion rather than fission, making the explosion relatively “clean” for its size.

The bomb was about 8 metres long, about 2.1 metres in diameter and weighed around 27 tonnes. It was too large to fit inside any existing bomber, so a Tupolev Tu-95 was specially modified, with its bomb-bay doors removed and the fuselage fuel tanks taken out. A huge parachute was fitted to slow the bomb’s fall so the aircraft could get away. Its main canopy was reported to cover about 1,600 square metres, and it had to be developed and tested separately because nothing of that size had been built before.

The test, 30 October 1961

Khrushchev publicly announced the coming test of a 50-megaton device in a speech to the 22nd Congress of the Communist Party on 17 October 1961. The United Nations General Assembly passed a resolution on 27 October urging the Soviet Union not to carry it out, but the test went ahead.

On the morning of 30 October the Tu-95, commanded by Major Andrei Durnovtsev, took off from Olenya airbase on the Kola Peninsula. It was accompanied by a Tu-16 laboratory aircraft to observe and measure the blast. Both planes were painted with reflective white paint to reduce heat damage.

The bomb was released at an altitude of about 10.5 kilometres over the Sukhoy Nos test site on Novaya Zemlya. Slowed by its parachute, it detonated at 11:32 Moscow time roughly 4 kilometres above the ground. By then the bomber was about 45 kilometres away. The shock wave caused the aircraft to drop sharply in altitude, but the crew regained control and landed safely.

Ionisation of the atmosphere caused by the blast interrupted radio communications across the region for some time, so ground controllers were briefly unable to contact the aircraft. Instruments on the ground and in the Tu-16 recorded the explosion, and cameras filmed the rising fireball and cloud from great distances.

Effects of the explosion

The fireball reached an estimated diameter of about 8 kilometres. It was prevented from touching the ground by the shock wave reflected from the surface. The mushroom cloud rose to an estimated 60 to 67 kilometres, well into the mesosphere, and spread to a width of roughly 95 kilometres at its top.

The flash was reportedly visible about 1,000 kilometres away. Observers estimated that the heat could have caused third-degree burns at a distance of around 100 kilometres. Buildings in a deserted settlement tens of kilometres from ground zero were destroyed, and window panes were reported broken in parts of Norway and Finland.

The atmospheric pressure wave was detected by instruments around the world and is reported to have circled the Earth three times. Because the explosion took place in the air and most of its energy came from fusion, local fallout was limited relative to its size, but it still added to global radioactive contamination from the 1961–1962 test series. Seismographs registered the explosion as a tremor equivalent to an earthquake of roughly magnitude 5.

By the numbers

Key people

• Nikita Khrushchev: the Soviet leader who ordered the test as a show of strength.
• Yuli Khariton: scientific director of Arzamas-16, responsible for Soviet nuclear weapon design.
• Andrei Sakharov: a leading designer of Soviet thermonuclear weapons, later a prominent dissident and winner of the 1975 Nobel Peace Prize.
• Andrei Durnovtsev: the pilot who commanded the Tu-95 that dropped the bomb.

Consequences and legacy

Militarily, Tsar Bomba changed little. A weapon of its weight could only be delivered by a slow, vulnerable aircraft, and both superpowers were moving towards missiles carrying smaller, more accurate warheads. No weapon of this size was ever put into service.

Politically, however, the test had a strong impact. It came during a Soviet test series of nearly 60 explosions in the autumn of 1961, and the United States resumed atmospheric testing in April 1962. Western governments condemned the test as an act of intimidation, and the Nordic countries, closest to the Arctic test site, protested strongly about the danger of fallout. American officials argued publicly that such a huge weapon added little to military power, and the United States did not attempt to match it. Public alarm about fallout grew in Europe and North America, helping to build support for the Partial Nuclear Test Ban Treaty of 1963, which ended atmospheric testing by its signatories.

The experience also influenced Sakharov. Already uneasy about fallout and its health effects, he increasingly campaigned against atmospheric testing and later became one of the Soviet Union’s best-known human rights advocates.

In August 2020 the Russian state nuclear corporation Rosatom released a previously classified documentary film of the test. A casing of the same type is displayed at the nuclear weapons museum in Sarov.

Myths and facts

Myth: Tsar Bomba was a 100-megaton bomb. The design was capable of about 100 megatons, but the device actually tested was deliberately reduced to around 50 megatons.

Myth: the bomber crew were not expected to survive. The crew’s chances were considered uncertain, which is why the parachute and reflective paint were used, but the mission was planned with their survival in mind, and they returned safely.

Timeline

• 1955, 22 November: The Soviet Union tests its first two-stage thermonuclear bomb.
• 1958, autumn: An informal moratorium on nuclear testing begins.
• 1961, 13 August: East Germany begins sealing the border in Berlin.
• 1961, 1 September: The Soviet Union resumes nuclear testing.
• 1961, 17 October: Khrushchev announces a coming 50-megaton test at the 22nd Party Congress.
• 1961, 27 October: The UN General Assembly appeals to the Soviet Union not to conduct the test.
• 1961, 30 October: Tsar Bomba is detonated over Novaya Zemlya.
• 1963, 5 August: The Partial Nuclear Test Ban Treaty is signed in Moscow.
• 2020, August: Rosatom releases declassified film of the test.

Why it matters

Tsar Bomba marked the extreme point of the race to build ever-larger nuclear weapons. It showed that there was virtually no technical limit to the size of a hydrogen bomb, and also that such size had little military purpose. Its sheer scale fed public fears of nuclear war and contributed to the first steps towards limiting nuclear testing.