In 1961, the Soviet Union tested a nuclear bomb so powerful that it would have been too big to use in war. And it had far-reaching effects of a very different kind.

On the morning of 30 October 1961, a Soviet Tu-95 bomber took off from Olenya airfield in the Kola Peninsula in the far north of Russia.

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The Tu-95 was a specially modified version of a type that had come into service a few years earlier; a huge, swept-wing, four-engined monster tasked with carrying Russia’s arsenal of nuclear bombs.  

The last decade had seen enormous strides in Soviet nuclear research. World War Two had placed the US and USSR in the same camp, but the post-war period had seen relations chill and then freeze. And the Soviets, presented with a rivalry against the world’s only nuclear superpower, had only one option – to catch up. Fast.

On 29 August 1949, the Soviets had tested their first nuclear device – known as ‘Joe-1’ in the West – on the remote steppes on what is now Kazakhstan, using intelligence gleaned from infiltrating the US’s atomic bomb programme. In the intervening years, their test programme had surged in leaps and starts, detonating more than 80 devices; in 1958 alone, the Soviet tested 36 nuclear bombs.

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But nothing the Soviet Union had tested would compare to this.

The Tu-95 carried an enormous bomb underneath it, a device too large to fit inside the aircraft’s internal bomb-bay, where such munitions would usually be carried. The bomb was 8m long (26ft), had a diameter of nearly 2.6m (7ft) and weighed more than 27 tonnes. It was, physically, very similar in shape to the ‘Little Boy’ and ‘Fat Man’ bombs which had devastated the Japanese cities of Hiroshima and Nagasaki a decade-and-a-half earlier. The bomb had become known by a myriad of neutral technical designations – Project 27000, Product Code 202, RDS-220, and Kuzinka Mat (Kuzka’s Mother). Now it is better known as Tsar Bomba – the ‘Tsar’s bomb’.

Tsar Bomba was no ordinary nuclear bomb. It was the result of a feverish attempt by the USSR’s scientists to create the most powerful nuclear weapon yet, spurred on by Premier Nikita Khruschchev’s desire to make the world tremble at the might of Soviet technology. It was more than a metal monstrosity too big to fit inside even the largest aircraft – it was a city destroyer, a weapon of last resort.

The Tupolev, painted bright white in order to lessen the effects of the bomb’s flash, arrived at its target point. Novya Zemlya, a sparsely populated archipelago in the Barents Sea, above the frozen northern fringes of the USSR. The Tupolev’s pilot, Major Andrei Durnovtsev, brought the aircraft to Mityushikha Bay, a Soviet testing range, at a height of about 34,000ft (10km). A smaller, modified Tu-16 bomber flew beside, ready to film the ensuing blast and monitor air samples as it flew from the blast zone.

In order to give the two planes a chance to survive – and this was calculated as no more than a 50% chance – Tsar Bomba was deployed by a giant parachute weighing nearly a tonne. The bomb would slowly drift down to a predetermined height – 13,000ft (3,940m) – and then detonate. By then, the two bombers would be nearly 50km (30 miles) away. It should be far enough away for them to survive.

On Novya Zemlya, the effects were catastrophic

Tsar Bomba detonated at 11:32, Moscow time. In a flash, the bomb created a fireball five miles wide. The fireball pulsed upwards from the force of its own shockwave. The flash could be seen from 1,000km (630 miles) away.

The bomb’s mushroom cloud soared to 64km (40 miles) high, with its cap spreading outwards until it stretched nearly 100km (63 miles) from end to end. It must have been, from a very far distance perhaps, an awe-inspiring sight.

On Novaya Zemlya, the effects were catastrophic. In the village of Severny, some 55km (34 miles) from Ground Zero, all houses were completely destroyed (this is the equivalent to Gatwick airport being destroyed by a bomb that had fallen on Central London). In Soviet districts hundreds of miles from the blast zone, damage of all kinds – houses collapsing, roofs falling in, damage to doors, windows shattering – were reported. Radio communications were disrupted for more than an hour.

Durovtsev’s Tupolev was lucky to survive; the blast wave from Tsar Bomba caused the giant bomber to plummet more than 1,000m (3,300ft) before the pilot could regain control.

One Soviet cameraman who witnessed the detonation said:

“The clouds beneath the aircraft and in the distance were lit up by the powerful flash. The sea of light spread under the hatch and even clouds began to glow and became transparent. At that moment, our aircraft emerged from between two cloud layers and down below in the gap a huge bright orange ball was emerging. The ball was powerful and arrogant like Jupiter. Slowly and silently it crept upwards... Having broken through the thick layer of clouds it kept growing. It seemed to suck the whole Earth into it. The spectacle was fantastic, unreal, supernatural.”

Tsar Bomba unleashed almost unbelievable energy – now widely agreed to be in the order of 57 megatons, or 57 million tons of TNT. That is more than 1,500 times that of the Hiroshima and Nagasaki bombs combined, and 10 times more powerful than all the munitions expended during World War Two. Sensors registered the bomb’s blast wave orbiting the Earth not once, not twice, but three times.

Because the fireball had not made contact with the Earth, there was a surprisingly low amount of radiation

Such a blast could not be kept secret. The US had a spyplane only tens of kilometres from the blast. It carried a special optical device called a bhangmeter useful for calculating the yield of far-off nuclear explosions. Data from this aircraft – codenamed Speedlight – was used by the Foreign Weapons Evaluation Panel to calculate this mystery test’s yield.

International condemnation soon followed, not only from the US and Britain, but from some of the USSR’s Scandinavian neighbours such as Sweden. The only silver lining in this mushroom cloud was that because the fireball had not made contact with the Earth, there was a surprisingly low amount of radiation.

It could have been very different. But for a change in its design to rein in some of the power it could unleash, Tsar Bomba was supposed to have been twice as powerful.

***

One of the architects of this formidable device was a Soviet physicist called Andrei Sakharov – a man who would later become world famous for his attempts to rid the world of the very weapons he had helped create. He was a veteran of the Soviet atomic bomb programme from the very beginning, and had been part of the team that had built some of the USSR’s earliest atom bombs.

Sakharov began work on a layered fission-fusion-fission device, a bomb that would create further energy from the nuclear processes in its core. This involved wrapping deuterium – a stable isotope of hydrogen – with a layer of unenriched uranium. The uranium would capture neutrons from the igniting deuterium and would itself start to react. Sakharov called it the sloika, or layered cake. This breakthrough allowed the USSR to build its first hydrogen bomb, a device much more powerful than the atomic bombs of only a few years before.

Sakharov had been told by Khrushchev to come up with a bomb that was more powerful than anything else tested so far.

The Soviet Union needed to show that it could pull ahead of the US in the nuclear arms race, according to Philip Coyle, the former head of US nuclear weapons testing under President Bill Clinton, who spent 30 years helping design and test atomic weapons. “The US had been very far ahead because of the work it had done to prepare the bombs for Hiroshima and Nagasaki. And then it did a large number of tests in the atmosphere before the Russians even did one.

“We were ahead and the Soviets were trying to do something to tell the world that they were to be reckoned with. Tsar Bomba was primarily designed to cause the world to sit up and take notice of the Soviet Union as an equal,” says Coyle.

The original design – a three layered bomb, with uranium layers separating each stage – would have had a yield of 100 megatons – 3,000 times the size of the Hiroshima and Nagasaki bombs. The Soviets had already tested large devices in the atmosphere, equivalent to several megatons, but this would have been far, far bigger. Some scientists began to believe it was too big.

With such immense power, there would be no guarantee that the giant bomb wouldn’t swamp the north of the USSR with a vast cloud of radioactive fallout.

It was the beginning of his journey from being a bomb designer to becoming a dissident – Frank von Hippel

That was of particular concern to Sakharov, says Frank von Hippel, a physicist and head of Public and International Affairs at Princeton University.

“He was really apprehensive about the amount of radioactivity it would create,” he says, “and the genetic effects that could have on future generations

“It was the beginning of his journey from being a bomb designer to becoming a dissident.”

Before it was ready to be tested, the uranium layers that would have helped the bomb achieve its enormous yield were replaced with layers of lead, which lessened the intensity of the nuclear reaction.

The Soviets had built a weapon so powerful that they were unwilling to even test it at its full capacity. And that was only one of the problems with this devastating device.

The Tu-95 bombers built to carry the Soviet Union’s nuclear weapons were designed to carry much lighter weapons. The Tsar Bomba was so big that it couldn’t be placed on a missile, and so heavy that the planes designed to carry it wouldn’t have been able to take them all the way to their targets with enough fuel. And, if the bomb was as powerful as intended, the aircraft would have been on a one-way mission anyway.

Even where nuclear weapons are concerned, there can be such as thing as too powerful, says Coyle, who is now a leading member of the Center for Arms Control and Non-Proliferation, a think tank based in Washington DC. “It’s hard to find a use for it unless you want to knock down very large cities,” he says. “It simply would be too big to use.”

Von Hippel agrees. “These things [large free-falling nuclear bombs] were designed that if you wanted to be able to destroy the target even if you were a mile off, it could be done. Things moved in a different direction – increasing missile accuracy and multiple warheads.”

It’s hard to find a use for it unless you want to knock down very large cities – Philip Coyle

Tsar Bomba had other effects. Such was the concern over the test – which was 20% of the size of every atmospheric test combined before it, von Hippel says – that it hastened the end of atmospheric testing in 1963. Von Hippel says that Sakharov was particularly worried by the amount of radioactive carbon 14 that was being emitted into the atmosphere – an isotope with a particularly long half-life. “This has been partly mitigated by all the fossil fuel carbon in the atmosphere which has diluted it,” he says.

Sakharov worried that a bomb bigger than the one tested would not be repelled by its own blastwave – like Tsar Bomba had been – and would cause global fallout, spreading toxic dirt across the planet.

Sakharov become an ardent supporter of the 1963 Partial Test Ban, and an outspoken critic of nuclear proliferation and, in the late 1960s, anti-missile defences that he feared would spur another nuclear arms race. He became increasingly ostracised by the state, a dissident against oppression who would in 1975 be awarded the Nobel Peace Prize, and referred to as “the conscience of mankind”, says von Hippel.

Tsar Bomba, it seems, may have had fallout of a very different kind.

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