Operation Ivy

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For the ska punk band, see Operation Ivy (band).
Operation Ivy
Ivy Mike
Country United States
Test site Elugelab (Flora), Enewetak Atoll; Runit (Yvonne), Enewetak Atoll
Period 1952
Number of tests 2
Test type dry surface, free air drop
Max. yield 10.4 megatonnes of TNT (44 PJ)
Previous test series Operation Tumbler–Snapper
Next test series Operation Upshot–Knothole

Operation Ivy was the eighth series of American nuclear tests, coming after Tumbler-Snapper and before Upshot-Knothole. Its purpose 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 Eniwetok Atoll in the Pacific Proving Ground in the Marshall Islands.



The first Ivy shot, Mike, was the first successful full-scale test of a multi-megaton thermonuclear weapon ("hydrogen bomb") using the Teller-Ulam design. Unlike later thermonuclear weapons, Mike used deuterium as its fusion fuel, maintained as a liquid by an expensive and cumbersome cryogenic system. It was detonated on Elugelab Island yielding 10.4 megatons, almost 500 times the yield of the bomb dropped on Nagasaki. Eight megatons of the yield was from fast fission of the uranium tamper, creating massive amounts of radioactive fallout. The detonation left an underwater crater 6,240 ft (1.9 km) wide and 164 ft (50 m) deep where Elugelab Island had been. Following this successful test, the Mike design was weaponized as the EC-16, but it was quickly abandoned for solid-fueled designs after the success of the Castle Bravo shot.

Jimmy P. Robinson,[1] a USAF captain, was lost while piloting his F-84G through the mushroom cloud to collect air samples; he ran out of fuel and attempted to land on water but was never found.[2]


The second test, King, fired the largest nuclear weapon to date using only nuclear fission (no fusion nor fusion boosting). This "Super Oralloy Bomb" was intended as a backup if the fusion weapon failed. King yielded 500 kilotons, 25 times more powerful than the Fat Man weapon.


United States' Ivy series tests and detonations
Name [note 1] Date time (UT) Local time zone [note 2][3] Location [note 3] Elevation + height [note 4] Delivery,[note 5]
Purpose [note 6]
Device [note 7] Yield [note 8] Fallout [note 9] References Notes
Mike 31 October 1952 19:14:59.4 MHT (11 hrs)
Elugelab (Flora), Enewetak Atoll 11°39′57″N 162°11′21″E / 11.66573°N 162.18928°E / 11.66573; 162.18928 (Mike) 2 m (6 ft 7 in) + 8 m (26 ft) dry surface,
weapons development
TX-5 primary "Sausage" 10.4 Mt [4][5][6][7] Megaton device. First true experimental H-bomb, used cryogenic deuterium; became TX-16 weapon. Elugelab completely cratered.
King 15 November 1952 23:30:00.0 MHT (11 hrs)
Runit (Yvonne), Enewetak Atoll 11°33′32″N 162°20′43″E / 11.55878°N 162.34541°E / 11.55878; 162.34541 (King) 0 + 450 m (1,480 ft) free air drop,
weapons development
Mk-18F SOB 500 kt [4][5][6][7] Kiloton device. Aka Super oralloy bomb (SOB), used 4 critical masses of U235. Largest pure fission device; also tested chain safety device.


  1. ^ "Into the Mushroom Cloud | History of Flight | Air & Space Magazine". airspacemag.com. Retrieved 2012-11-01. 
  2. ^ Michael Robert Patterson. "Jimmy Priestly Robinson, Captain, United States Air Force". arlingtoncemetery.net. Retrieved 2012-11-01. 
  3. ^ "Timezone Historical Database". iana.com. Retrieved 2014-03-08. 
  4. ^ a b Sublette, Carey, Nuclear Weapons Archive, retrieved 2014-01-06 
  5. ^ a b Hansen, Chuck (1995), The Swords of Armageddon, Vol. 8, Sunnyvale, CA: Chukelea Publications, ISBN 978-0-9791915-1-0 
  6. ^ a b United States Nuclear Tests: July 1945 through September 1992 (DOE/NV-209 REV15), Las Vegas, NV: Department of Energy, Nevada Operations Office, 2000-12-01, retrieved 2013-12-18 
  7. ^ a b Yang, Xiaoping; North, Robert; Romney, Carl (August 2000), CMR Nuclear Explosion Database (Revision 3), SMDC Monitoring Research 

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