Ivy Mike

Coordinates: 11°40′0″N 162°11′13″E / 11.66667°N 162.18694°E / 11.66667; 162.18694
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Ivy Mike
Detonation and subsequent mushroom cloud of the "Mike" shot (in fast motion).
CountryUnited States
Marshall Islands
Test seriesOperation Ivy
Test siteEnewetak, Trust Territory of the Pacific Islands
DateNovember 1, 1952
(71 years ago)
Test typeAtmospheric
Yield10.4 megatons of TNT
Test chronology

Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion.[1][2][3] Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in Enewetak Atoll, in the now independent island nation of the Marshall Islands, as part of Operation Ivy. It was the first full test of the Teller–Ulam design, a staged fusion device.[4]

Due to its physical size and fusion fuel type (cryogenic liquid deuterium), the "Mike" device was not suitable for use as a deliverable weapon. It was intended as a "technically conservative" proof of concept experiment to validate the concepts used for multi-megaton detonations.[4]

Samples from the explosion had traces of the isotopes plutonium-246, plutonium-244, and the predicted elements einsteinium and fermium.[5]


Beginning with the Teller–Ulam breakthrough in March 1951, there was steady progress made on the issues involved in a thermonuclear explosion and there were additional resources devoted to staging, and political pressure towards seeing, an actual test of a hydrogen bomb.[6]: 137–139  A date within 1952 seemed feasible.[7]: 556  In October 1951 physicist Edward Teller pushed for July 1952 as a target date for a first test, but project head Marshall Holloway thought October 1952, a year out, was more realistic given how much engineering and fabrication work the test would take and given the need to avoid the summer monsoon season in the Marshall Islands.[8]: 482  On June 30, 1952, United States Atomic Energy Commission chair Gordon Dean showed President Harry S. Truman a model of what the Ivy Mike device would look like; the test was set for November 1, 1952.[7]: 590 

One attempt to significantly delay the test, or not hold it at all, was made by the State Department Panel of Consultants on Disarmament, chaired by J. Robert Oppenheimer, who felt that avoiding a test might forestall the development of a catastrophic new weapon and open the way for new arms agreements between the United States and the Soviet Union.[6]: 139–142  The panel lacked political allies in Washington, however, and no test delay was made on this account.[6]: 145–148 

There was a separate desire voiced for a very short delay in the test, for more political reasons: it was scheduled to take place just a few days before the November 4 holding of the United States presidential election, 1952.[8]: 497  Truman wanted to keep the thermonuclear test away from partisan politics but had no desire to order a postponement of it himself; however he did make it known that he would be fine if it was delayed past the election due to "technical reasons" being found.[7]: 590–591 [8]: 497–498  Atomic Energy Commission member Eugene M. Zuckert was sent to the Enewetak test site to see if such a reason could be found, but weather considerations – on average there were only a handful of days each month that were suitable for the test – indicated it should go ahead as planned, and in the end no schedule delay took place.[7]: 590–592 [8]: 498 

Device design and preparations[edit]

A view of the "Sausage" device casing, with its instrumentation and cryogenic equipment attached. The long pipes were for measurement purposes; their function was to transmit the first radiation from the "primary" and "secondary" stages (known as "Teller light") to instruments just as the device was detonated, before being destroyed in the explosion. Note man seated lower right for scale.

The 82 short tons (74 metric tons) "Mike" device was essentially a building that resembled a factory rather than a weapon.[9] It has been reported that Soviet engineers derisively referred to "Mike" as a "thermonuclear installation".[10]: 391 

The device was designed by Richard Garwin, a student of Enrico Fermi, on the suggestion of Edward Teller. It had been decided that nothing other than a full-scale test would validate the idea of the Teller-Ulam design. Garwin was instructed to use very conservative estimates when designing the test, and told that it need not be small and light enough to be deployed by air.[11]: 327 

Liquid deuterium was chosen as the fuel for the fusion reaction because its use simplified the experiment from a physicist's point of view, and made the results easier to analyze. From an engineering point of view, its use necessitated the development of previously unknown technologies to handle the difficult material, which had to be stored at extremely low temperatures, near absolute zero.[9]: 41–42  A large cryogenics plant was built to produce liquid hydrogen (used for cooling the device) and deuterium (fuel for the test). A 3,000 kilowatts (4,000 hp) power plant was also constructed for the cryogenics facility.[9]: 44 

The device that was developed for testing the Teller-Ulam design became known as a "Sausage" design:[9]: 43 

  • At its center was a cylindrical insulated steel Dewar (vacuum flask) or cryostat. This tank, almost 7 ft (2.1 m) across and more than 20 ft (6.1 m) high,[9]: 43  had walls almost 30 cm (0.98 ft) thick.[12] It weighed approximately 54 short tons (49 metric tons).[13] It was capable of holding 1,000 L (260 U.S. gal) of liquid deuterium, cooled to near-absolute zero.[14][15] The cryogenic deuterium provided the fuel for the "secondary" (fusion) stage of the explosion.[9]: 43 
  • At one end of the cylindrical Dewar flask was a TX-5[16]: 66  regular fission bomb (not boosted[16]: 43 ). The TX-5 bomb was used to create the conditions needed to initiate the fusion reaction. This "primary" fission stage was nested inside the radiation case at the upper section of the device, and was not in physical contact with the "secondary" fusion stage. The TX-5 did not require refrigeration.[16]: 43 [9]: 43–44 
  • Running down the center of the Dewar flask within the secondary was a cylindrical rod of plutonium within a chamber of tritium gas. This "fission sparkplug" was imploded by x-rays from the primary detonation. That provided a source of outward-moving pressure inside the deuterium and increased conditions for the fusion reaction.[9]: 43–44 
  • Surrounding the assembly was a 5 short tons (4.5 metric tons) natural uranium "tamper". The exterior of the tamper was lined with sheets of lead and polyethylene, forming a radiation channel to conduct X-rays from the "primary" to the "secondary" stage. As laid out in the Teller-Ulam design, the function of the X-rays was to compress the "secondary" with tamper/pusher ablation, foam plasma pressure and radiation pressure. This process increases the density and temperature of the deuterium to the level needed to sustain a thermonuclear reaction, and compress the "sparkplug" to a supercritical mass – inducing the "sparkplug" to undergo nuclear fission and to thereby start a fusion reaction in the surrounding deuterium fuel.[9]: 43–44 
The Ivy Mike shot cab and signal tower.

The entire "Mike" device (including cryogenic equipment) weighed 82 short tons (74 metric tons). It was housed in a large corrugated-aluminum building, called the shot cab, which was 88 ft (27 m) long, 46 ft (14 m) wide, and 61 ft (19 m) high, with a 300 ft (91 m) signal tower. Television and radio signals were used to communicate with a control room on the USS Estes where the firing party was located.[9]: 43–44 [17]: 42 

It was set up on the Pacific island of Elugelab, part of the Enewetak atoll. Elugelab was connected to the islands of Dridrilbwij (Teiteir), Bokaidrikdrik (Bogairikk), and Boken (Bogon) by a 9,000 ft (2.7 km) artificial causeway. Atop the causeway was an aluminum-sheathed plywood tube filled with helium ballonets, referred to as a Krause-Ogle box.[17]: 34  This allowed gamma and neutron radiation to pass uninhibited to instruments in an unmanned detection station, Station 202, on Boken Island. From there signals were sent to recording equipment at Station 200, also housed in a bunker on Boken Island. Personnel returned to Boken Island after the test to recover the recording equipment.[17]: 136, 138 

In total, 9,350 military and 2,300 civilian personnel were involved in the "Mike" shot.[17]: 2 The operation involved the cooperation of the United States army, navy, air force and intelligence services. The USS Curtiss brought components from the United States to Elugelab for assembly. Work was completed on October 31, at 5.00 p.m. Within an hour, personnel were evacuated in preparation for the blast.[9]: 43–44 


Ivy Mike test video.
Enewetak Atoll, before "Mike" shot. Note island of Elugelab on left.
Enewetak Atoll, after "Mike" shot. Note crater on left.

The test was carried out on 1 November 1952 at 07:15 local time (19:15 on 31 October, Greenwich Mean Time). It produced a yield of 10.4 megatons of TNT (44 PJ).[18][19] However, 77% of the final yield came from fast fission of the uranium tamper, which produced large amounts of radioactive fallout.[citation needed]

The fireball created by the explosion had a maximum radius of 2.9 to 3.3 km (1.8 to 2.1 mi).[20][21][22] The maximum radius was reached a number of seconds after the detonation, during which the hot fireball lifted up due to buoyancy. While still relatively close to the ground, the fireball had yet to reach its maximum dimensions and was thus approximately 5.2 km (3.2 mi) wide. The mushroom cloud rose to an altitude of 17 km (56,000 ft) in less than 90 seconds. One minute later it had reached 33 km (108,000 ft), before stabilizing at 41 km (135,000 ft) with the top eventually spreading out to a diameter of 161 km (100 mi) with a stem 32 km (20 mi) wide.[23]

The blast created a crater 1.9 km (6,230 ft) in diameter and 50 m (164 ft) deep where Elugelab had once been;[24] the blast and water waves from the explosion (some waves up to 6 m (20 ft) high) stripped the test islands clean of vegetation, as observed by a helicopter survey within 60 minutes after the test, by which time the mushroom cloud and steam were blown away. Radioactive coral debris fell upon ships positioned 56 km (35 mi) away, and the immediate area around the atoll was heavily contaminated.[25][26][27]

Close to the fireball, lightning discharges were rapidly triggered.[28] The entire shot was documented by the filmmakers of Lookout Mountain studios.[29] A post-production explosion sound was overdubbed over what was a completely silent detonation from the vantage point of the camera, with the blast wave sound only arriving a number of seconds later, as akin to thunder, with the exact time depending on its distance.[30] The film was also accompanied by powerful, Wagner-esque music featured on many test films of that period and was hosted by actor Reed Hadley. A private screening was given to President Dwight D. Eisenhower who had succeeded President Harry S. Truman in January 1953.[31]: 80  In 1954, the film was released to the public after censoring, and was shown on commercial television channels.[31]: 183 

Edward Teller, perhaps the most ardent supporter of the development of the hydrogen bomb, was in Berkeley, California, at the time of the shot.[32] He was able to receive first notice that the test was successful by observing a seismometer, which picked up the shock wave that traveled through the earth from the Pacific Proving Grounds.[33][8]: 777–778  In his memoirs, Teller wrote that he immediately sent an unclassified telegram to Dr. Elizabeth "Diz" Graves, the head of the rump project remaining at Los Alamos during the shot. The telegram contained only the words "It's a boy," which came hours earlier than any other word from Enewetak.[34][11]: 352 

Scientific discoveries[edit]

Mike mushroom cloud.

An hour after the bomb was detonated, U.S. Air Force pilots took off from Enewetak Island to fly into the atomic cloud and take samples. Pilots had to monitor extra readouts and displays while "piloting under unusual, dangerous, and difficult conditions” including heat, radiation, unpredictable winds and flying debris. "Red Flight" Leader Virgil K. Meroney flew into the stem of the explosion first. In five minutes, he had gathered all the samples he could, and exited. Next Bob Hagan and Jimmy Robinson entered the cloud. Robinson hit an area of severe turbulence, spinning out and barely retaining consciousness. He regained control of his plane at 20,000 feet, but the electromagnetic storm had disrupted his instruments. In rain and poor visibility, without working instruments, Hagan and Robinson were unable to find the KB-29 tanker aircraft to refuel.[5][17]: 96  They attempted to return to the field at Enewetak. Hagan, out of fuel, made an extraordinary successful dead-stick landing on the runway. Robinson's F-84 Thunderjet crashed and sank 3.5 miles short of the island. Robinson's body was never recovered.[5][35][36]

Fuel tanks on the airplane's wings had been modified to scoop up and filter passing debris. The filters from the surviving planes were sealed in lead and sent to Los Alamos, New Mexico for analysis. Radioactive and contaminated with calcium carbonate, the "Mike" samples were extremely difficult to handle. Scientists at Los Alamos found traces in them of isotopes plutonium-246 and plutonium-244.[5]

Al Ghiorso at the University of California, Berkeley speculated that the filters might also contain atoms that had transformed, through radioactive decay, into the predicted but undiscovered elements 99 and 100. Ghiorso, Stanley Gerald Thompson and Glenn Seaborg obtained half a filter paper from the Ivy Mike test. They were able to detect the existence of the elements einsteinium and fermium, which had been produced by intensely concentrated neutron flux about the detonation site. The discovery was kept secret for several years, but the team was eventually given credit. In 1955 the two new elements were named in honor of Albert Einstein and Enrico Fermi.[5][37][38]

Related tests[edit]

A simplified and lightened bomb version (the EC-16) was prepared and scheduled to be tested in operation Castle Yankee, as a backup in case the non-cryogenic "Shrimp" fusion device (tested in Castle Bravo) failed to work; that test was canceled when the Bravo device was tested successfully, making the cryogenic designs obsolete.[citation needed]


See also[edit]


  1. ^ "OPERATION GREENHOUSE - 1951". ATOMIC SHADOWS. Retrieved January 9, 2020.
  2. ^ The first small-scale thermonuclear test was the George explosion of Operation Greenhouse.
  3. ^ United States Nuclear Tests: July 1945 through September 1992 (PDF) (DOE/NV-209 REV15), Las Vegas, NV: Department of Energy, Nevada Operations Office, December 1, 2000, archived from the original (PDF) on June 15, 2010, retrieved December 18, 2013
  4. ^ a b Wellerstein, Alex (January 8, 2016). "A Hydrogen Bomb by Any Other Name". The New Yorker. Retrieved January 19, 2020.
  5. ^ a b c d e Chapman, Kit (January 14, 2020). "Element Hunting in a Nuclear Storm". Distillations. Science History Institute. Retrieved January 14, 2020.
  6. ^ a b c Bernstein, Barton J. (Fall 1987). "Crossing the Rubicon: A Missed Opportunity to Stop the H-Bomb?". International Security. 14 (2): 132–160. doi:10.2307/2538857. JSTOR 2538857. S2CID 154778522.
  7. ^ a b c d Hewlett, Richard G.; Duncan, Francis (1969). Atomic Shield, 1947–1952 (PDF). A History of the United States Atomic Energy Commission. Vol. 2. University Park, Pennsylvania: Pennsylvania State University Press.
  8. ^ a b c d e Rhodes, Richard (1 August 1995). Dark Sun: The Making of the Hydrogen Bomb. Simon & Schuster. ISBN 978-0-68-480400-2. LCCN 95011070. OCLC 456652278. OL 7720934M. Wikidata Q105755363 – via Internet Archive.
  9. ^ a b c d e f g h i j k Parsons, Keith M.; Zaballa, Robert A. (July 26, 2017). Bombing the Marshall Islands: A Cold War Tragedy. Cambridge University Press. pp. 41–46. ISBN 9781108508742.
  10. ^ Herken, Gregg (9 September 2002). "Notes for Chapter Fourteen "A Bad Business Now Threatening"". Brotherhood of the Bomb: The Tangled Lives and Loyalties of Robert Oppenheimer, Ernest Lawrence and Edward Teller (1st ed.). Henry Holt and Company. ISBN 978-0-80-506588-6. LCCN 2002017219. OCLC 890256840. OL 7932650M. Retrieved 10 November 2021 – via Internet Archive. p. 391: Mike was meant to be a proof-of-principle test of radiation implosion, and not a deliverable bomb. Housed in a six-story building, weighing more than 80 tons, the cryogenically-cooled device was later described disdainfully by the Russians as a "thermonuclear installation."
  11. ^ a b Teller, Edward; Schoolery, Judith (September 9, 2009). Memoirs: A Twentieth Century Journey In Science And Politics. Cambridge, MA: Perseus Publishing. ISBN 9780786751709.
  12. ^ "1 November 1952 – Ivy Mike". Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization. Retrieved 10 November 2021.
  13. ^ Dillingham, Clay, ed. (1 July 2015). "Atomic Photography: Blasts From The Past" (PDF). National Security Science. 15 (5). Los Alamos National Laboratory: 16–21. Retrieved 10 November 2021.
  14. ^ "Deuterium" (PDF). p. 8.
  15. ^ Reichhardt, Tony (November 2, 2017). "The First Hydrogen Bomb". Air & Space. Retrieved January 22, 2020.
  16. ^ a b c Hansen, Chuck (2007). The Swords of Armageddon: U.S. Nuclear Weapons Development Since 1945 (PDF) (CD-ROM & download available) (2nd ed.). Sunnyvale, California: Chukelea Publications. ISBN 978-0979191503. OCLC 231585284.
  17. ^ a b c d e Gladeck, F. R.; Hallowell, J. H.; Martin, E. J.; McMullan, F. W.; Miller, R. H.; et al. (1 December 1982). OPERATION IVY: 1952 (pdf) (Technical report). Washington, D.C.: Defense Nuclear Agency. DNA 6036F. Archived (PDF) from the original on 22 August 2021. Retrieved 10 November 2021.
  18. ^ Rowberry, Ariana (February 27, 2014). "Castle Bravo: The Largest U.S. Nuclear Explosion". Brookings. Retrieved January 9, 2020.
  19. ^ Fabry, Merrill (2 November 2015). "What the First H-Bomb Test Looked Like". History. Time. Vol. 186, no. 16. ISSN 0040-781X. OCLC 1311479. Archived from the original on 4 September 2021. Retrieved 10 November 2021. At 7:15 a.m. local time on Elugelab Island, Mike was detonated from a control ship 30 m. away. The detonation resulted in a massive explosion, equivalent to 10.4 Megatons of TNT.
  20. ^ Walker, John (June 2005). "Nuclear Bomb Effects Computer". Fourmilab. Retrieved November 22, 2009.
  21. ^ Walker, John (June 2005). "Nuclear Bomb Effects Computer Revised Edition 1962, Based on Data from The Effects of Nuclear Weapons, Revised Edition "The maximum fireball radius presented on the computer is an average between that for air and surface bursts. Thus, the fireball radius for a surface burst is 13 percent larger than that indicated and for an air burst, 13 percent smaller. "". Fourmilab. Retrieved November 22, 2009.
  22. ^ "Mock up". Remm.nlm.gov. Archived from the original on June 7, 2013. Retrieved November 30, 2013.
  23. ^ Blades, David M. Blades; Siracusa, Joseph M. (May 1, 2014). A History of U.S. Nuclear Testing and Its Influence on Nuclear Thought, 1945–1963. Rowman & Littlefield. p. 54. ISBN 9781442232013. Retrieved January 21, 2020.
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  25. ^ Froehlich, M.B.; Chan, W.Y.; Tims, S.G.; Fallon, S.J.; Fifield, L.K. (December 2016). "Time-resolved record of 236U and 239,240Pu isotopes from a coral growing during the nuclear testing program at Enewetak Atoll (Marshall Islands)". Journal of Environmental Radioactivity. 165: 197–205. doi:10.1016/j.jenvrad.2016.09.015. PMID 27764678.
  26. ^ Buesseler, Ken O.; Charette, Matthew A.; Pike, Steven M.; Henderson, Paul B.; Kipp, Lauren E. (April 2018). "Lingering radioactivity at the Bikini and Enewetak Atolls". Science of the Total Environment. 621: 1185–1198. Bibcode:2018ScTEn.621.1185B. doi:10.1016/j.scitotenv.2017.10.109. hdl:1912/9537. PMID 29096952.
  27. ^ Hughes, Emlyn W.; Molina, Monica Rouco; Abella, Maveric K. I. L.; Nikolić-Hughes, Ivana; Ruderman, Malvin A. (July 30, 2019). "Radiation maps of ocean sediment from the Castle Bravo crater". Proceedings of the National Academy of Sciences. 116 (31): 15420–15424. Bibcode:2019PNAS..11615420H. doi:10.1073/pnas.1903478116. PMC 6681739. PMID 31308235.
  28. ^ Colvin, J. D.; Mitchell, C. K.; Greig, J. R.; Murphy, D. P.; Pechacek, R. E.; Raleigh, M. (1987). "An empirical study of the nuclear explosion-induced lightning seen on IVY-MIKE". Journal of Geophysical Research. 92 (D5): 5696. Bibcode:1987JGR....92.5696C. doi:10.1029/JD092iD05p05696.
  29. ^ Chamberlain, Craig (January 14, 2019). "New book tells story of secret Hollywood studio that shaped the nuclear age". Illinois News Bureau.
  30. ^ "Nuclear Warfare Lecture 14 by Professor Grant J. Matthews of University of Notre Dame OpenCourseWare. Mechanical Shock velocity equation". Archived from the original on December 19, 2013.
  31. ^ a b Weart, Spencer (2012). The Rise of Nuclear Fear. Harvard University Press. p. 80. ISBN 9780674065062.
  32. ^ "THE ATOM: The Road Beyond Elugelab". Time. Vol. 63, no. 15. April 12, 1954. p. 23. Retrieved January 21, 2020.
  33. ^ Axelrod, Alan (December 10, 2009). The Real History of the Cold War: A New Look at the Past. Sterling. pp. 156. ISBN 9781402763021. Retrieved January 21, 2020.
  34. ^ Ford, Kenneth; Wheeler, John Archibald (June 18, 2010). Geons, Black Holes, and Quantum Foam: A Life in Physics. W. W. Norton & Company. p. 227. ISBN 9780393079487. Retrieved December 21, 2013.
  35. ^ "F-84G-5-RE Thunderjet Serial Number 51-1040". Pacific Wrecks. Retrieved January 9, 2020.
  36. ^ Wolverton, Mark (2009). "Into the Mushroom Cloud Most pilots would head away from a thermonuclear explosion". Air & Space Magazine (August). Smithsonian. Retrieved January 9, 2020.
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  38. ^ Nagy, Sandor (2009). Radiochemistry and Nuclear Chemistry. Vol. I. EOLSS Publications. pp. 91–92. ISBN 9781848261266. Retrieved January 21, 2020.

Further reading[edit]

External links[edit]

11°40′0″N 162°11′13″E / 11.66667°N 162.18694°E / 11.66667; 162.18694