| Ivy Mike | |
|---|---|
 Detonation and subsequentmushroom cloud of the"Mike" shot (in fast motion). | |
 | |
| Information | |
| Country | United States Marshall Islands |
| Test series | Operation Ivy |
| Test site | Enewetak, Trust Territory of the Pacific Islands |
| Date | November 1, 1952 (73 years ago) (1952-11-01) |
| Test type | Atmospheric |
| Yield | 10.4megatons of TNT |
| Test chronology | |
Ivy Mike was thecodename given to the first full-scale[note 1] test of athermonuclear device, in which a significant fraction of the explosiveyield comes fromnuclear fusion.[1][2][3]Ivy Mike was detonated on November 1, 1952, by theUnited States on the island ofElugelab inEnewetak Atoll, in the now independent island nation of theMarshall Islands, as part ofOperation Ivy. It was the first full test of theTeller–Ulam design, astaged fusion device.[4]
Due to its physical size and fusion fuel type (cryogenic liquiddeuterium), 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 isotopesplutonium-246,plutonium-244, and the predicted elementseinsteinium andfermium.[5]
Beginning with theTeller–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 physicistEdward Teller pushed for July 1952 as a target date for a first test, but project headMarshall 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 chairGordon Dean showed PresidentHarry 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 theState Department Panel of Consultants on Disarmament, chaired byJ. 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 theSoviet 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 the1952 presidential election.[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 memberEugene 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
The 82-short-ton (74-metric-ton) "Mike" device was 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 byRichard Garwin, a student ofEnrico Fermi, on the suggestion ofEdward Teller. It had been decided that nothing other than a full-scale test would validate the idea of theTeller-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
Liquiddeuterium 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, nearabsolute 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 3000 kW 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
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 onUSS Estes where the firing party was located.[9]: 43–44 [17]: 42
It was set up on the Pacific island ofElugelab, part of theEnewetak 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 analuminum-sheathedplywood tube filled withheliumballonets, referred to as aKrause-Ogle box.[17]: 34 This allowedgamma andneutron 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. TheUSSCurtiss 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
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 10.4megatons of TNT (44 PJ).[18][19]77% of the final yield came fromfast fission of the uranium tamper, which produced large amounts of radioactivefallout.[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 several seconds after the detonation, during which the hot fireball lifted up due tobuoyancy. 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. Themushroom 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 ofLookout Mountain studios.[29] Apost-production explosion sound wasoverdubbed over what was a completely silent detonation from the vantage point of the camera, with the blast wave sound only arriving later, as akin tothunder, 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 actorReed Hadley. A private screening was given to PresidentDwight D. Eisenhower who had succeeded PresidentHarry 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 inBerkeley, California, at the time of the shot.[32] He was able to receive first notice that the test was successful by observing aseismometer, which picked up theshock wave that traveled through the earth from thePacific Proving Grounds.[33][8]: 777–778 In his memoirs, Teller wrote that he immediately sent an unclassified telegram toDr. Elizabeth "Diz" Graves, the head of the rump project remaining atLos 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
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" LeaderVirgil 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, entering a spin 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 a successfuldead-stick landing on the runway. Robinson'sF-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 toLos Alamos, New Mexico for analysis. Radioactive and contaminated withcalcium carbonate, the "Mike" samples were extremely difficult to handle. Scientists at Los Alamos found traces in them of isotopesplutonium-246 andplutonium-244.[5]
Al Ghiorso at theUniversity 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 andGlenn Seaborg obtained half a filter paper from the Ivy Mike test. They were able to detect the existence of the elementseinsteinium andfermium, 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 ofAlbert Einstein andEnrico Fermi.[5][37][38]
A simplified and lightened bomb version (theEC-16) was prepared and scheduled to be tested in operationCastle Yankee, as a backup in case the non-cryogenic "Shrimp" fusion device (tested inCastle Bravo) failed to work; that test was canceled when the Bravo device was tested successfully, making the cryogenic designs obsolete.[citation needed]
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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."
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.
11°40′0″N162°11′13″E / 11.66667°N 162.18694°E /11.66667; 162.18694
