Ivy King

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Ivy King was the explosion of the largest pure fission nuclear bomb ever tested by the United States. The bomb was tested during the Truman administration as part of Operation Ivy, the development of very powerful atomic weapons in response to the nuclear weapons program of the Soviet Union.

The production of this device was hurried so it would be ready if its sister project, Ivy Mike, failed in its attempt to achieve a thermonuclear reaction. In the event, the Ivy Mike test took place a fortnight before the testing of this device (although that test was not of a practical air-droppable weapon).

On November 16, 1952 at 11:30 local time (23:30 GMT) a B-36H bomber dropped the bomb over a point 2,000 feet North of Runit Island in the Enewetak atoll, resulting in a 500 kiloton explosion at 1480 feet (450 m).

The Ivy King bomb, designated as a Mk-18 bomb and named the "Super Oralloy Bomb", was a modified version of the Mk-6D bomb. Instead of using an implosion system similar to the Mk-6D, it used a 92 point implosion system initially developed for the Mk-13. Its uranium-plutonium core was replaced by 60kg of highly enriched uranium (HEU) fashioned into a thin-walled sphere equivalent to approximately four critical masses. The thin-walled sphere was a commonly used design which ensured that the fissile material remained sub-critical until imploded. The HEU sphere was then enclosed in a natural uranium tamper. To physically prevent the HEU sphere collapsing into a critical condition if the surrounding explosives were detonated, or if the sphere was crushed following an aircraft accident, the hollow centre was filled with a chain made from aluminium and boron which was pulled out to arm the bomb. The boron coated chain also absorbed the neutrons needed to drive the nuclear reaction.

The primary designer of the Super Oralloy Bomb, physicist Ted Taylor, later became a vocal proponent of nuclear disarmament.

[edit] References

Chuck Hansen (1988). U. S. Nuclear Weapons: The Secret History. Arlington: AeroFax.
Chuck Hansen (1995) Swords of Armageddon. Published on CD-Rom only by Chukelea, Sunnyvale, CA.