Operation Ivy was the eighth series of American nuclear tests, coming after Tumbler-Snapper and before Upshot-Knothole. The purpose of the tests was to help upgrade the U.S. arsenal of nuclear weapons, in response to the Soviet nuclear weapons program. The two explosions were staged in late 1952 at the Pacific Proving Ground in the Marshall Islands.
The first device, codenamed Mike, was notable for being the first successful test of a multi-megaton thermonuclear weapon design (the Teller-Ulam design), usually considered the world's first hydrogen bomb test. It used liquid deuterium as its fusion fuel, kept cold with an expensive and cumbersome cryogenic system. It was detonated on Elugelab Island in the Enewetak atoll of the Marshall Islands. It yielded 10.4 megatons of explosive power, almost 500 times the power of the bomb that was dropped on Nagasaki. 8 megatons of the yield was from fast fission of the uranium tamper. The detonation obliterated Elugelab, leaving an underwater crater 6,240 ft (1.9 km) wide and 164 ft (50 m) deep where the island had been. Following this successful test a bomb known as either the EC-16 or TX-16 was developed to allow deployment in the event of a national emergency.
The second test, King, was a test of the largest nuclear weapon ever built at the time which utilized only nuclear fission as the source of its energy (it had none of its energy added from fusion or fusion boosting). It was dubbed the "Super Oralloy Bomb", and was intended as a backup if the fusion weapon was a failure. It had a yield of 500 kilotons, 25-40 times more powerful than the weapons dropped during World War II.
Jimmy P. Robinson, a USAF captain, was lost during the test after executing his mission of piloting his F-84G through the mushroom cloud to collect air samples; he ran out of fuel and attempted to land the craft on the water, but was never found.