On 30 October 1961, the largest nuclear weapon ever constructed was set off over Novaya Zemlya Island in the Russian Arctic Sea. The Soviet ‘Tsar Bomba’ had a yield of 50 megatons, or the power of around 3,800 Hiroshima bombs detonated simultaneously. While its official designation was RDS-220 hydrogen bomb, the Tsar Bomba was given its nickname by the West in an analogy with two other huge Russian objects, the Tsar Bell and the Tsar Cannon, the largest of their kind in the world.

The test came amid rising political tensions between the United States and the Soviet Union. On 1 September 1961, the testing moratorium that had been in place for almost three years was broken. Within 16 months, both countries conducted more nuclear tests than in the 16 preceding years, causing a spike in global radiation levels and the further escalation of political tension before the Cuban Missile Crisis. 

Soviet Premier Nikita Khrushchev had ordered the development of a 100 megaton weapon in July 1961, leaving the engineers only 14 weeks before the first test. Unlike normal thermonuclear weapons, the Tsar Bomba comprised a third stage, whereas thermonuclear warheads usually comprise only two. By adding more stages, the explosive power of a thermonuclear bomb can theoretically be increased indefinitely. Soviet engineers had reduced the actual yield of 100 megatons by around half to limit fallout.

The bomb was air-dropped in order to demonstrate its deliverability. A huge fall-retardation parachute was attached to the bomb to increase the plane’s chances of escape. The Tu-95 bomber was also coated with a special white reflective paint to protect it from the thermal radiation released by the explosion. Nonetheless, the probability of survival for pilot Andrei Durnovtsev and his crew had been estimated at only 50%. The explosion’s shock wave caused the plane to instantly lose one kilometre of altitude but it landed safely, nonetheless.

Although the Tsar Bomba was detonated 4 kilometres above ground, a seismic shock wave equivalent to an earthquake of over 5.0 on the Richter Scale was measured around the world. The mushroom cloud reached a height of 60 kilometres. Third degree burns were possible at a distance of hundreds of kilometres. The ring of absolute destruction had a 35km radius - shown right using a map of Paris to illustrate the impact. Using the online Nukemap application by U.S. nuclear weapons historian Alex Wellerstein, the impact of a Tsar Bomba-scale nuclear explosion can be illustrated for any location in the world.

Its immense yield, large weight and bulky dimensions made the Tsar Bomba impractical for use as a military weapon. In particular, it could not be delivered via ballistic missile. The Tsar Bomba was therefore never deployed and remained a one-time display of superiority.

After a total of 715 nuclear tests, the Russian Federation signed the Comprehensive Nuclear-Test-Ban Treaty (CTBT) on 24 September 1996, the very day it opened for signature, and ratified it on 30 June 2000.

Scene from 'Trinity and Beyond: The Atomic Bomb Movie' (1995) by Peter Kuran