Ivy Mike: The First H-Bomb

It was on this day 61 years ago that the world entered the thermonuclear era. At the Enewetak Atoll, the arms race entered a new and dangerous phase as a device that made the terrible explosives used on Hiroshima and Nagasaki at the end of World War II look like ants was detonated.

Background:

In 1949, the Soviet Union successfully detonated its first atomic device- RDS-1. It was modeled on the Fat Man device dropped on Nagasaki and had a similar yield. While the United States had earlier added more powerful weapons to its stockpile as demonstrated in tests such as Operation Greenhouse, the Soviets acquired the bomb years earlier than expected, and Washington was alarmed that it may lose its preeminence in atomic weapons if it failed to push the envelope and test more powerful bombs.

The RDS-1 test convinced President Truman that it was necessary to develop a hydrogen bomb, where part of the explosive yield would be produced by nuclear fusion.

A fusion device was speculated about as early as the Manhattan Project, but the possibility had never been seriously attempted until this time.

The Project:

Edward Teller, a veteran of the Manhattan Project and the main advocate of the idea of a hydrogen bomb since then, was called in to work on the new project at Los Alamos National Laboratory. What emerged out of all the complicated physics was the Teller-Ulam device- a sort of layered bomb wherein one fission reaction would set off a fusion reaction, followed by another fission reaction.

This was a breakthrough. Not only did it demonstrate that a hydrogen bomb was theoretically possible, but the design also broke free of any limits to a bomb's destructive power. While a classical fission device like the bombs used up to this point had an upper limit in terms of destructive power (the 500 kiloton Ivy King bomb, the second shot in the Operation Ivy series, was the most powerful non-thermonuclear device ever tested), thermonuclear bombs do not have any such limit. In theory, it would be possible to build a hydrogen bomb powerful enough to destroy a planet for instance (though finding enough fissile material to do this would certainly be a problem!). This would be done by adding additional fusion-fission stages to the bomb.

The Device:

Codenamed "Sausage," the Ivy Mike device was not actually designed by Edward Teller himself, but Richard Garwin, on Teller's suggestion. It was massive, weighing 73.8 metric tons and was two-stories tall. Part of the reason for the size of the device was the need for supercooled liquid fuel to induce the fusion reactions.

The Sausage device, to the left

The Shot:

Edward Teller was not present for the final test of his design (as the video above shows). The time scheduled for the detonation was 7:14 A.M. local time. The test was a success. The mushroom cloud reached a maximum height of 36.5 kilometers and had a diameter of 96.5 kilometers (Nuclear Weapon Archive). Ivy Mike vaporized the island it stood on and left a large crater that is still visible today, as seen below:

The estimated yield of the blast was 10.4 megatons- hundreds of times more powerful than any atomic device ever detonated before that point.

As I suspect you've seen by now in the above video, Edward Teller received the news of the successful test not from a telephone, but by using a seismograph. His simple message back to Los Alamos was "It's a boy." This signified that the project to develop a hydrogen bomb was successful.

Aftermath:

The successful detonation of the Sausage device proved that the Teller-Ulam design worked in reality. Ivy Mike however, was far too big to be weaponized. It was merely a rather fiery and spectacular experiment that proved that the hydrogen bomb design was sound. The Soviets derisively called Ivy Mike something like a fusion factory- because that's what it was. Nevertheless, the arms race would now take an even more explosive and dangerous turn. Operation Ivy touched off the next wave of testing to weaponize the hydrogen bomb- Operation Castle, which would produce weapons even more fearsome.

See also:

Making the H-Bomb (more background, including the economic and geopolitical context)
Operation Ivy project film
Operation Ivy at Nuclear Weapon Archive Operation Ivy Mike Thermonuclear Weapon Cold War

Weapons of War: The Tsar Bomba

52 years ago today- October 30th, 1961, at the nuclear test site at Novaya Zemlya, the Soviet Union detonated the most powerful weapon ever manufactured by mankind. With a staggering yield of 50 megatons of TNT (that's 50 million tons), the aptly named Tsar or 'Emperor Bomb' was more than twice as powerful as the next most powerful nuke tested. Actual footage of the detonation is below:

The Tsar Bomba was the climax of the high-yield thermonuclear weapons tests conducted by the superpowers in the 1950's and early 1960's. These were the times where the nuclear weapons detonations that we all know were captured on camera (after 1963, the Partial Test Ban Treaty went into effect and all subsequent testing was conducted underground).

Background:

No nuclear testing had been conducted by either the Soviet Union or the United States since 1958. Tensions remained high however, and as the 1960's began, the Soviets wanted to send a very loud message, timing it for the meeting of the 22nd Soviet Congress.

The Bomb:

Staggeringly, the Soviets' original intention was for the construction of a 100 megaton device. However there were numerous problems that began to become apparent as the numbers began to be crunched by the scientists. The first problem was the very high likelihood that the pilots flying the plane that would drop the bomb would be killed in the ensuing blast (as it turned out, they barely had enough time to safely get out of the way of the final 50 megaton version- and that was with a parachute to slow the bomb's fall). The second problem was the very high fallout that the 100 megaton version was expected to generate. It was also calculated that most of the energy of such a large weapon would radiate into space, making it very inefficient.

To reduce these risks, a uranium tamper inside the device was replaced with a lead one. Thus there would be less fissile and radioactive material. This reduced the yield by approximately 50%.

Like all thermonuclear weapons (popularly known as the hydrogen bomb), it was a multi-staged "Teller-Ulam" device. However unlike most, the Tsar Bomba was a three-staged weapon, whereas most thermonuclear weapons only contain two stages (I'll get into the nitty gritty of this science in an upcoming post).

The Test Results:

The bomb's detonation caused the aircraft that dropped it to fall many thousands of meters. The fireball was visible from 1,000 kilometers away. A person standing 100 kilometers from ground zero would still have gotten third degree burns, and windows were broken as far away as Finland. The mushroom cloud stretched into the mesosphere- around 60 kilometers high. The shockwave from the explosion circled the planet three times before it dissipated.

Aftermath:

Fortunately, the Tsar Bomba was far too big to be of practical use as a weapon. It was simply a very huge and ominous show of force. Nevertheless, it increased tensions between the superpowers and set off a new wave of nuclear testing.

The next two years would see the Cold War reach the tipping point of becoming the hottest one in history- the annihilation of civilization almost seemed imminent in the wake of the Cuban Missile Crisis. Cooler heads prevailed in the end, and tensions were reduced through the Partial Test Ban Treaty. As the 1960's rolled on, missile technology improved to the point of allowing smaller, more accurate nuclear weapons to be delivered more efficiently, and monster double-digit megaton bombs became unnecessary.

The Tsar Bomba is ultimately a curiosity- showcasing the destructive potential of man and serving as a dire warning that failure to communicate is no longer an option in the nuclear age.

See Also:

Nuke Calculator at SD.net (This tool allows the user to experiment with varying nuclear weapon yields and see the approximate results)
The Tsar Bomba at Nuclear Weapon Archive Soviet Union Tsar Bomba Cold War Nuclear Weapons Hydrogen