Ivy Mike was the code name given to the first test of a multi-stage thermonuclear weapon, detonated on October 31, 1952 by the United States. The device was the first full test of the Teller-Ulam principle for a "staged" hydrogen bomb.

The "Mike" device used a TX-5 boosted nuclear fission bomb as its "primary" stage. The "secondary" stage used liquid deuterium fusion fuel stored in a cylindrical flask. Running down the center of the flask was a cylindrical rod of plutonium (the "sparkplug") to ignite the fusion reaction. Surrounding this assembly was a five-ton natural uranium tamper. The interior of the casing was lined with sheets of lead and polyethylene foam, which formed a radiation channel to conduct heat from the primary to secondary. The outermost layer was a steel casing 10-12 inches thick. The entire "Sausage" (as it was nicknamed) assembly measured 80 inches in diameter and 244 inches in height, and weighed 82 tons.

The shot cab that housed the Mike device was set up on the Pacific Island of Elugelab, part of Enewetak Atoll. An 9,000-foot long artificial causeway connected the islands of Elugelab, Teiter, Bogairikk, and Bogon. Atop this causeway was an aluminium-sheathed plywood tube filled with helium ballonets. This allowed gamma and neutron radiation to pass uninhibited to an unmanned detection station on Bogon.

In total, 9,350 military and 2,300 civilian personnel were involved in the Mike shot. The test was carried out 0715 hours local time on November 1, 1952. The mushroom cloud rose to an altitude of 57,000 feet in less than 90 seconds. One minute later it had reached 108,000 feet, before stabilizing at 120,000 feet.

The blast stripped the test islands clean of vegetation, and blasted out a crater 6,240 feet in diameter where Elugelab once stood. Chunks of irradiated coral fell upon ships stationed 30 miles from the blast, and the immediate area around the atoll was heavily contaminated for some time. Although the test yielded 10.4 megatons, 77% of the final yield came from fast fission of the uranium tamper.

Only 408 personnel are said to have received no radiation following the test. The entire shot was filmed, and a private screening was given to President Dwight D. Eisenhower. It was later released to the public, and was for many days played continuously on many television channels.

The Mike shot was followed on November 16 by Ivy King. Ivy King was a test of the Mk 18 Super Oralloy bomb, airdropped from a B-36 and detonated at 1,480 feet. It yielded 500 kilotons, the most powerful purely fission bomb up to that time.

See also

• Castle Bravo
• History of nuclear weapons

References

• Richard Rhodes, Dark Sun: The Making of the Hydrogen Bomb (New York: Simon and Schuster, 1995).