|Fig. 1: Stages of explosion in a Teller-Ulam design. (Source: Wikimedia Commons)|
Ivy Mike was a hydrogen bomb that ushered the world into the thermonuclear age on November 1, 1952. Built under the Truman administration, Ivy Mike was - at its construction - the largest, heaviest and most powerful bomb in existence. The device detonated in the test, nicknamed "The Sausage", was the first true hydrogen bomb ever tested, that is, the first thermonuclear device built upon the Teller-Ulam principles of staged radiation implosion. 
Hydrogen bombs rely on nuclear fusion to source their destructive power. Two atoms of smaller elements, like Hydrogen, combine to make an atom of a larger, heavier element; thereby releasing immense amounts of nuclear energy. The problem is that such a process requires tremendous heat and pressure to be initiated.
In 1951, Stanislaw Ulam and Edward Teller produced a design that could theoretically generate such conditions within a bomb and initiate nuclear fusion. The idea was to put a bomb on top of a bomb (Fig. 1-A).  The first bomb was a traditional nuclear fission device, which would blow up and - for a very small amount of time - be held in place by its casing (Fig. 1-B). The heat and force thus generated would be channeled downwards and hit the store of hydrogen - the second bomb - placed beneath (Fig. 1-C).  With enough force, it was conjectured, the fusion process would begin in the lower device (Fig. 1-D) and a hydrogen bomb would be created (Fig. 1-E).
|Fig. 2: The Island of Elugelab, before and after the Ivy Mike detonation.  (Source: Wikimedia Commons)|
Ivy Mike was the test created to prove Teller-Ulam's brainchild. It used a TX-5 fission bomb as the primary stage, and a secondary stage consisting of liquid deuterium fusion fuel stored in a cylindrical Dewar flask. Surrounded by a natural uranium tamper weighing more than 5 metric tons, the Dewar had a plutonium "spark-plug" rod running down its center that ignited the fusion reaction.  Weighing over 82 tons, the entire assembly was housed in an enormous steel casing - 80 inches wide and 244 inches long, with walls about 10-12 inches thick. The inside surface of the casing was lined with sheets of lead and polyethylene to form the radiation channel that conducted heat from the primary bomb to the secondary source. To keep the liquid deuterium from evaporating, over 18 tonnes of cryogenic cooling was attached to the assembly.  Built at Elugelab, an island on the Enewetak atoll in the Pacific Proving Grounds, Ivy Mike looked more like an aircraft hangar or factory rather than a bomb to be deployed from a plane.
Before Ivy Mike, no one exactly knew what a man-made thermonuclear explosion would create; only hypotheses existed. But Mike's detonation cleared away any lingering doubts the world had about the destructive power of a thermonuclear bomb.
The almost 11-megaton explosion created a fireball 5 kilometers across, and a mushroom cloud that climbed to 57,000 feet within 90 seconds, eventually stabilizing at 120,000 feet. Ten minutes later, it had spread out to about 100 miles.  About 77% - 8 megatons - of the yield came from the fast fission of the natural uranium tamper, with the remainder coming from fusion of the deuterium fuel.  Radioactive coral debris fell on ships positioned over 35 miles from ground zero, and the immediate area around the atoll was heavily contaminated for some time to come. The intense concentration of neutron flux around the detonation site produced two new elements, Einsteinium and Fermium; the first synthetic elements ever created by man. 
As for Elugelab, the island was entirely wiped out; it does not appear in modern Atlases anymore. In its place was left a dark blue welt in the ocean, almost 2 miles across and deep enough to hold a 17-story building.  Over the next 30 years, the US put hundreds of millions of dollars into decontaminating the atoll, finally declaring the area safe for living in 1980.
The explosion was the 4th largest ever tested by the United States.  The US once again had the upper hand in the nuclear race (after Soviet Union successfully testing its own atomic device in 1949) with a significantly more powerful hydrogen bomb. However, it was only a matter of time that the Soviet Union caught up by creating its own thermonuclear bomb in 1955. 
© Aditya Singh. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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