Everything about Ivy Mike totally explained
Ivy Mike was the codename given to the first US test of a
fusion device where a major part of the explosive yield came from fusion. It was detonated on
November 1,
1952 by the
United States at 11.6709 N, 162.1980 E on
Enewetak, an
atoll in the Pacific Ocean, as part of
Operation Ivy. The device was the first full test of the
Teller-Ulam design, a
staged fusion bomb, and is generally considered the first successful test of a hydrogen bomb.
Due to its physical size and fusion fuel type (
cryogenic liquid
deuterium) the Mike device wasn't suitable for use as a
thermonuclear weapon; it was intended as an extremely conservative experiment to validate the concepts used for multi-megaton detonations. 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 cancelled when the Bravo device was tested successfully, making the cryogenic designs obsolete.
Device design and preparations
The "John", a 62 ton device, was essentially a building that resembled a factory rather than a weapon. It has been reported that Russian engineers derisively referred to Mike as a "thermonuclear installation". At its center, a very large cylindrical
thermos flask or
cryostat, held the cryogenic deuterium fusion fuel. A regular
fission bomb (the "primary") at one end was used to create the conditions needed to initiate the fusion reaction.
The device was designed by
Richard Garwin, a student of
Enrico Fermi's, 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, and Garwin was instructed to use very conservative estimates when designing the test, and that it need not be deployable. (That is, it need not be small, light, and sturdy enough to be carried by an airplane and dropped on a target.)
The primary stage was a TX-5 boosted fission bomb in a separate space atop the assembly (so it wouldn't freeze, rendering it inoperable). The "secondary" fusion stage used liquid deuterium despite the difficulty of handling this material, because this fuel simplified the experiment, and made the results easier to analyze. Running down the center of the flask which held it was a cylindrical rod of
plutonium (the "sparkplug") to ignite the fusion reaction. Surrounding this assembly was a five-ton (4.5 tonne) natural
uranium "tamper". The interior of the tamper was lined with sheets of
lead and
polyethylene foam, which formed a
radiation channel to conduct
X-rays from the primary to secondary. (The function of X-rays was to hydrodynamically compress the secondary, increasing the density and temperature of the deuterium to the levels needed to sustain the thermonuclear reaction, and compressing the sparkplug to
supercriticality ignition.) The outermost layer was a steel casing 10-12 inches (25-30 cm) thick. The entire assembly, nicknamed "Sausage", measured 80 inches (2.03 m) in diameter and 244 inches (6.19 m) in height and weighed about 60 tons (54 tonnes).
The entire Mike device (including cryogenic equipment) weighed 82 tons (73.8 tonnes), and was housed in a large corrugated-aluminium building called a "shot cab" which was set up on the Pacific island of
Elugelab, part of the
Enewetak atoll.
A 9,000-foot (2.7 km) artificial causeway connected the islands of Elugelab, Teiter, Bogairikk, and Bogon. Atop this causeway was an
aluminium-sheathed
plywood tube (named a "Krause-Ogle box") filled with
helium ballonets. This allowed
gamma and
neutron radiation to pass uninhibited to an unmanned detection station housed in a bunker on Bogon.
In total, 9,350 military and 2,300 civilian personnel were involved in the Mike shot. A large cryogenics plant was installed on Parry Island, at the South end of the Eniwetak atoll, to produce the liquid hydrogen (used for cooling the device) and deuterium needed for the test.
Detonation
The test was carried out at 0715 local time on
November 1,
1952; it produced a yield of 10.4
megatons. However, 77% of the final yield came from
fast fission of the uranium tamper, which meant that the device produced large amounts of
fallout.
The fireball was over 3 miles (5 km) wide, and the mushroom cloud rose to an altitude of 57,000 feet (17.0 km) in less than 90 seconds. One minute later it had reached 108,000 feet (33.0 km), before stabilizing at 120,000 feet (37.0 km) with the top eventually spreading out to a diameter of 100 miles (161 km) with a stem 20 miles (32 km) wide.
The blast created a crater 6,240 feet (1.9 km) in diameter and 164 feet (50 m) deep where Elugelab had once been; the blast and water waves from the explosion (some waves up to twenty feet 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 had been blown away. Irradiated coral debris fell upon ships stationed 30 miles (48 km) from the blast, and the immediate area around the atoll was heavily contaminated for some time.
The entire shot was documented by the filmmakers of
Lookout Mountain studios. The film was accompanied by powerful,
Wagner-esque music featured on many test films of that period and was hosted by actor
Reed Hadley. After the test a private screening was given to President
Dwight D. Eisenhower. It was later released to the public after censoring, and was for many days played continually on many television channels.
Edward Teller, who was perhaps the most ardent supporter of the development of the hydrogen bomb, was in
Berkeley, California, at the time of the shot. He was able to receive first notice that the test was successful by observing a
seismometer, which picked up the
shock wave travelling through the earth all the way from the
South Pacific test site. In his memoirs, Teller wrote that he immediately sent an unclassified telegram to his colleagues at
Los Alamos which contained only the words—for security purposes—"It's a boy."
Further Information
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