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An unearthly spectacle: The untold story of the world’s biggest bomb via the Bulletin of Atomic Scientists

By Alex Wellerstein


The flash alone lasted more than a minute. The fireball expanded to nearly six miles in diameter—large enough to include the entire urban core of Washington or San Francisco, or all of midtown and downtown Manhattan. Over several minutes it rose and mushroomed into a massive cloud. Within ten minutes, it had reached a height of 42 miles and a diameter of some 60 miles. One civilian witness remarked that it was “as if the Earth was killed.” Decades later, the weapon would be given the name it is most commonly known by today: Tsar Bomba, meaning “emperor bomb.”

Designed to have a maximum explosive yield of 100 million tons (or 100 megatons) of TNT equivalent, the 60,000-pound monster bomb was detonated at only half its strength. Still, at 50 megatons, it was more than 3,300 times as powerful as the atomic bomb that killed at least 70,000 people in Hiroshima, and more than 40 times as powerful as the largest nuclear bomb in the US arsenal today. Its single test represents about one tenth of the total yield of all nuclear weapons ever tested by all nations.[2]

At the time of its detonation, the Tsar Bomba held the world’s attention, largely as an object of infamy, recklessness, and terror. Within two years, though, the Soviet Union and the United States would sign and ratify the Limited Test Ban Treaty, prohibiting atmospheric nuclear weapons testing, and the 50-megaton bomb would fall into relative obscurity.

From the very beginning, the United States sought to minimize the importance of the 50-megaton test, and it became fashionable in both the United States and the former Soviet Union to dismiss it as a political stunt with little technical or strategic importance. But recently declassified files from the Kennedy administration now indicate that the Tsar Bomba was taken far more seriously as a weapon, and possibly as something to emulate, than ever was indicated publicly. And memoirs from former Soviet weapons workers, only recently available outside Russia, make clear that the gigantic bomb’s place in the history of Soviet thermonuclear weapons may be far more important than has been appreciated. Sixty years after the detonation, it’s now finally possible to piece together a deeper understanding of the creation of the Tsar Bomba and its broader impacts.

The Tsar Bomba is not just a subject for history; some of the same dynamics exist today. It is not just the story of a single weapon that was detonated six decades ago, but a parable about political posturing and technical enablement that applies just as acutely today. In a new era of nuclear weapons and delivery competition, the Tsar Bomba is a potent example of how nationalism, fear, and high-technology can combine in a fashion that is ultimately dangerous, wasteful, and pointless.


A few days later, Seaborg met with weapons scientists to discuss building high-yield weapons. Betts initiated a discussion with Sandia National Laboratory over the feasibility of dropping weapons with yields of 30 or 50 megatons from a B-52, which would require using drogue parachutes to ensure the survival of the pilots. At the same time, a team of Livermore scientists got together to review the possibilities of a US return to nuclear testing. Along with ideas relating to more optimized designs and “clean” bombs deriving most of their yield from fusion, they were intrigued once again by Teller’s possibility of bigger bangs: “USSR high-yield tests have reawakened interest in high-yield testing by the United States. High-yield weapons (50 megatons to 1,000 megatons) should be reconsidered and re-evaluated for their possible military use.”[34] Again, let that sink in: Even after denouncing the Tsar Bomba as pointless terrorism, there were scientists and military planners working for the US government who were considering nuclear weapons with yields 20 times larger.

In early 1962, one scientist at the Sandia lab reported to his colleagues about this sudden interest in superbombs, noting dryly that the Soviet detonation had “started some thinking in this country that there must be a good application for these things that has escaped our attention… the military would like to see the development of a few [very high-yield] bombs and would even feel good if a few were in the stockpile even though no known targets justify such weapons.”[35]


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