At 11:32 Moscow time on 30 October 1961, a Soviet Tu-95V bomber over the Novaya Zemlya archipelago in the Arctic released a bomb eight metres long and about 27 tonnes in weight. It fell under a parachute for just over three minutes. When it went off, about 4,000 metres above the Mityushikha Bay test range, it released the energy of roughly 50 million tonnes of TNT. It remains the most powerful explosion humans have ever caused.

A Bomber Built Around One Bomb

The weapon was too big for any normal bomb bay. The Tu-95V was a Bear modified with an enlarged, strengthened bomb bay. The aircraft was painted in white anti-flash paint, down to the propeller blades. Alongside flew a twin-jet Tu-16, fitted as a flying laboratory with cameras, telemetry and pressure recorders to film and measure the blast.

The pilot was Major Andrei Durnovtsev, 38. The problem facing his crew was simple: a 50-megaton burst would destroy any aircraft nearby. The answer was a parachute system with a main canopy of about 1,600 square metres, which weighed on the order of 800 kilograms on its own. It slowed the bomb so much that it took about 188 seconds to fall from 10,500 to 4,000 metres.

45 Kilometres Away

That time let the Tu-95V get roughly 45 kilometres away before the burst. It was not enough to make the flight comfortable. The shock wave caught the bomber and threw it down by somewhere between 800 and 1,000 metres, depending on the account, before the crew regained control and flew home. Durnovtsev was promoted to lieutenant colonel and made a Hero of the Soviet Union.

On the ground, the fireball swelled almost to the height of the release aircraft. The mushroom cloud rose to about 64 kilometres, seven times the height of Everest, and spread to roughly 90 kilometres across. The flash was seen about 1,000 kilometres away despite cloud. Buildings in the settlement of Severny, 55 kilometres from ground zero, were destroyed. Windows were broken hundreds of kilometres away, and the Atomic Heritage Foundation reports panes broken as far as Norway and Finland, where the shock wave was focused by the atmosphere. Instruments recorded the pressure wave travelling around the Earth three times.

Why Only Half of It Went Off

Khrushchev had asked for a 100-megaton weapon. The three-stage design could have delivered it, but the designers replaced the uranium tamper of the final stage (and possibly the second) with lead. That roughly halved the yield and cut the fallout dramatically: about 97 percent of the energy came from fusion, making it, for its size, an unusually clean bomb. A full-yield test would also have left the bomber no realistic chance of escaping.

The bomb was designed in about sixteen weeks at Arzamas-16 by a team that included Andrei Sakharov, Viktor Adamsky, Yuri Babayev, Yuri Smirnov and Yuri Trutnev, under the institute’s scientific director Yuli Khariton. Sakharov later turned against nuclear testing and became a leading Soviet dissident; he was awarded the Nobel Peace Prize in 1975, though Moscow would not let him travel to Oslo to receive it.

The Film

Soviet cameras filmed the whole operation, from loading the bomb to the cloud. The footage stayed secret until 20 August 2020, when Rosatom, the Russian state nuclear corporation, released a 30-minute documentary to mark 75 years of the Russian nuclear industry.

What the Popular Version Gets Right

The widely shared account is mostly right: 30 October 1961, a bomb of about 27 tonnes and 8 metres, a parachute of around 800 kilograms, a bomber roughly 45 kilometres away at detonation, a flash seen about 1,000 kilometres off, a yield of 50 megatons from a 100-megaton design reduced by swapping uranium for lead, and a film kept secret until August 2020. Three details need correcting. The cloud reached about 64 kilometres, not 67; no reliable source gives the often-quoted 8-kilometre fireball width, only that it rose almost to the bomber’s height. And Sakharov did not oversee the project alone: he was one of its leading designers in a team at Arzamas-16 headed by Yuli Khariton.

Sources: Carey Sublette, Nuclear Weapon Archive, “Big Ivan, The Tsar Bomba”; Atomic Heritage Foundation, “Tsar Bomba” (2014); Air & Space Magazine, “King of the Bombs”; The War Zone, Thomas Newdick (24 August 2020); The Barents Observer (August 2020); Rosatom documentary film (20 August 2020); Andrei Sakharov, Memoirs.