Tsar Bomba was a Soviet hydrogen bomb detonated on 30 October 1961, and at about 50 megatons it remains the largest nuclear explosion ever produced. [1] Rosatom, the Russian state nuclear corporation, released declassified test footage of it in August 2020. [2, 3] For how it compares with the Hiroshima bomb, see Tsar Bomba vs Little Boy.
The explosion
The flash of the detonation was seen about 1,000 km away. [4] The pressure wave was so strong that it was detected circling the Earth three times. [4, 5] The fireball was large enough that it reached down to the ground and up to nearly the height from which the bomb had been released. [4] Rosatom's declassified footage, released in August 2020, shows the fireball and the rising cloud from several camera positions. [3]
How big the bomb was
The bomb itself was about 8 metres long and 2.1 metres across, and weighed roughly 27 tonnes, with sources giving a range of 24.5 to 27.5 tonnes. [4] It was too big to fit inside the bomb bay, so it was carried partly recessed, with more than half of it protruding, and lowered on a specially developed parachute that slowed its fall and gave the aircraft time to fly clear. [4] By the time the bomb detonated, the aircraft was about 45 km away. [4]
Where and when it was tested
Tsar Bomba was tested at 11:32 Moscow time on 30 October 1961 at the Mityushikha Bay test site on the west coast of Novaya Zemlya, test field D-2 near Cape Sukhoy Nos. [4, 5] It was carried by a Tu-95V bomber (Carey Sublette designates the aircraft a Tu-95N) flown by Major Andrei Durnovtsev. [5, 4] The bomb was released from about 10,500 m and burst at about 4,000 m above the test field. [4]
The mushroom cloud
The mushroom cloud rose into the stratosphere. Estimates of its height range from about 64 km (Sublette) to 67 km (the Bulletin of the Atomic Scientists), with the Atomic Heritage Foundation and the National WWII Museum giving about 40 miles. [4, 2, 5] Within about ten minutes the cloud cap had spread roughly 60 miles across. [2]
50 megatons tested against a 100-megaton design
Tsar Bomba was designed for about 100 megatons, [5] but it was tested at roughly half that. For the test the uranium tamper was replaced with lead, which roughly halved the yield and cut the fallout; about 97% of the energy released came from fusion, making it one of the cleanest large explosions relative to its yield. [4] Later US assessments put the yield as high as about 57 megatons. [4] No more powerful weapon has been tested since. You can detonate Tsar Bomba over any city on the nuclear blast radius calculator or its weapon page.