On October 30, 1961, a Soviet Tu-95V bomber dropped a single 27-ton bomb over Novaya Zemlya, a remote Arctic island. The detonation released approximately 50 megatons of TNT equivalent — more than 3,300 times the yield of the Hiroshima bomb and more than ten times the combined yield of all explosives used in World War II. To this day no weapon has been detonated bigger.
The 100-megaton design
Tsar Bomba was originally designed to yield 100 megatons. The bomb was a three-stage thermonuclear device with a fission primary, a lithium-deuteride fusion secondary, and a uranium-238 tertiary jacket that would have undergone fast fission from the secondary's neutron flux.
For the test, the U-238 jacket was replaced with lead. This roughly halved the yield — the U-238 fast-fission stage would have been responsible for about half the original 100 Mt yield — but it also reduced fallout by approximately 97%. Khrushchev personally ordered the substitution: a clean 50 Mt test was politically more useful than a dirty 100 Mt test.
Even at 50 Mt, the test was the cleanest in history relative to its yield, with about 97% of the energy coming from fusion rather than fission.
Delivery and detonation
The bomb was so heavy (27 tons) that the modified Tu-95V bomber could not close its bomb-bay doors with the weapon loaded. To survive the detonation, the bomb was suspended from a giant parachute that slowed its descent and gave the Tu-95V time to fly to a safe distance. Even so, the crew's estimated probability of survival was given as only 50%.
At 11:32 a.m. Moscow time, the bomb detonated at an altitude of about 4,000 m above the test site at Sukhoy Nos on Novaya Zemlya. The yield was later assessed at 50 to 58 megatons, depending on source — the largest nuclear explosion ever produced by humans.
The fireball and mushroom cloud
The fireball reached approximately 8 km in diameter — large enough that its lower edge nearly touched the ground despite the high-altitude burst, and its upper edge reached roughly the altitude of a commercial airliner. The fireball was visible at a distance of more than 1,000 km, and observers in Norway and Finland (north of the test site) reported a brilliant flash of light.
The mushroom cloud rose to about 67 km altitude — well into the stratosphere and seven times the height of Mount Everest. The cloud cap reached 95 km in diameter. The Tu-95V crew, who had flown about 50 km from ground zero by detonation time, were briefly knocked out of formation by the shock wave but survived.
Effects at distance
The blast wave from Tsar Bomba was detected three times as it circled the planet. At Dikson, a Soviet weather station 800 km from ground zero, all wooden buildings were destroyed and stone buildings were damaged. At Severny, an island 400 km away, the windows of every building were shattered.
On the island of Novaya Zemlya itself, all buildings within 55 km of ground zero were leveled. Wooden houses collapsed, telephone poles snapped, and seismographs as far as 1,000 km away registered the blast as a magnitude 5 earthquake.
The thermal pulse from Tsar Bomba was strong enough to cause 3rd-degree burns on exposed skin out to 100 km, and to start fires up to 35 km away.
Why no one tested anything bigger
After Tsar Bomba, no state ever designed or tested a more powerful weapon. The reasons are practical, not political. First, a 100-megaton weapon offers diminishing returns: because blast radius scales with the cube root of yield, doubling the yield from 50 Mt to 100 Mt only multiplies blast radius by about 1.26. The marginal additional damage is not worth the cost.
Second, the size and weight of multi-megaton bombs make them impractical to deliver. Tsar Bomba required a specially modified bomber and a parachute system; an ICBM cannot carry such a payload at intercontinental range.
Third, by the early 1970s the move was firmly toward lower-yield, higher-accuracy MIRVed warheads. A Trident II SLBM carrying eight 475-kiloton W88 warheads delivers more total destruction than a single 50-megaton weapon — at any chosen set of targets.
Tsar Bomba in modern arsenals
Tsar Bomba was a one-off test article. The Soviet Union never deployed a weapon of comparable yield. Modern Russian strategic warheads (the RS-28 Sarmat, for example) carry warheads of typically 750 kt to a few megatons, comparable to US strategic warheads. The largest currently deployed warhead worldwide is in the low single-digit megatons.
Tsar Bomba is best understood as the technological maximum of a particular design philosophy — one that the major nuclear powers ultimately abandoned in favor of accuracy and MIRV. Its main legacy today is symbolic: it remains the loudest demonstration in history of just how much energy a single explosion can release. The simulator includes Tsar Bomba in its weapons database; you can detonate it over any city to see the radii.