The Tsar Bomba was one of the most fearsome devices ever built, a multistage hydrogen bomb that shattered the idea that there were any technological limits to the destructiveness of atomic weaponry.
After the Soviet Union detonated a 50-megaton bomb over an uninhabited island north of the Arctic Circle October 30, 1961, it was clear that human beings would need to consciously decide to curtail atomic yields, since science had imposed so few limits on them. The Tsar Bomba was a glimpse of how enormous a human-made nuclear explosion could be.
Its yield of 50 megatons, or 50,000 kilotons, was equal to 3,800 of the bombs dropped on Hiroshima, or to 50 million tons of TNT.
“The mushroom cloud reached a height of 60 kilometers [37 miles],” according to the website of the Comprehensive Test-Ban Treaty Organization. “Third-degree burns were possible at a distance of hundreds of kilometers. The ring of absolute destruction had a 35 km [28-mile] radius.”
The Tsar Bomba’s fireball was over 5 miles in width. According to the NukeMap, a project of nuclear historian Alex Wellerstein, if the Tsar Bomba were dropped over Business Insider’s headquarters at 20th Street and Fifth Avenue in Manhattan, the “radiation zone” would stretch from north of Times Square to south of the Brooklyn Bridge. The radiation zone is the area in which between 50% and 90% of people would die if they didn’t receive medical assistance.
The fireball would stretch from Brooklyn Heights to the American Museum of Natural on the Upper West Side of Manhattan:
The “thermal radiation radius” — where there’s near certainty of people receiving third-degree burns — would swallow pretty much the entire New York metropolitan area:
And it could have been even larger. Then Soviet Premier Nikita Khrushchev originally wanted to test a 100-megaton weapon. Plans were scaled back when researchers realized that such a device would produce dangerous fallout that could pollute areas far beyond the bomb’s test site.
As the Nuclear Weapons Archive notes, the bomb’s design wasn’t technologically path-breaking and “pushed no envelopes, saved for size.” The weapon used a thermonuclear detonation to trigger an additional and even larger explosion, a process that could be used to produce ever-larger blasts.
But the Tsar Bomba would represent the high-water mark of explosive output. A bomb of its yield had little practical applicability: It was large enough in size to make it nearly impossible to deliver using ballistic missiles, and in a battlefield scenario it would potentially kill as many friendlies as enemies.
Miniaturization was, and is, a more important technical hurdle than sheer atomic yield for the would-be nuclear weapons power, which needs bombs that are small and light enough to fit on ballistic missiles more than it needs ones that produce a city-sized fireball.
The Tsar Bomba test came during a period when the US was trying to build high-yield thermonuclear devices that it could practicably deliver by air, the aspiration behind the disastrous Castle Bravo test that the US carried out in the Pacific in 1954.
According to authors Michael Fitzgerald and Michael Packwood, the Tsar Bomba was a means of projecting Soviet power, and Khrushchev’s own strength, during one of the tensest stretches of the Cold War, a time when the Berlin Wall was under construction and the US’s missile capabilities were worryingly ahead of Moscow’s.
Krushchev had at least proven that the Soviets had built a weapon with a horrifying yield — a contemporary BBC report on the test notes that British officials were immediately aware that the Soviets had managed an unprecedentedly large blast.
But the Cuban Missile Crisis, and the Soviet removal of nuclear-capable missiles from the Western Hemisphere, would come roughly a year after the Tsar Bomba test, which seemed to pay no real strategic dividend for Moscow.
The US and the Soviet Union saw that there was no point in building a bomb that could never really be delivered via missile, and that was awkward to deliver by plane. No test of its magnitude was ever attempted by either side.
But it’s a reminder that such devices have been within the human race’s technological capabilities for decades now, and that it’s only their lack of a practical application — and not any insurmountable technical barriers — that has prevented ever larger and more alarming weapons from being built.