When was the Castle Bravo test performed?
3247662#4
In 1994, a 1953 "Castle Bravo" program prospectus was found which included reference to Project 4.1 apparently written before the "Bravo" shot had occurred. The U.S. government responded that someone had gone back into the project list after the "Bravo" test to insert Project 4.1; thus, according to the U.S. government, the acts were not premeditated. All other U.S. documents point to Project 4.1 having been established after the "Bravo" test—most sources point to its having been organized on March 7, 1954. The final Project 4.1 report began in its preface with the statement that "Operation CASTLE did not include a biomedical program" (it mentions this in discussing the ad hoc nature by which the project personnel were assembled). All official and mainstream historical accounts of the "Bravo" test indicate that its high level of fallout was a result of a miscalculation in relation to its design and was not deliberate (see the Castle Bravo article for more information on the alleged accident).
Project 4.1
827611#23
The decision to carry out the Bravo test under the prevailing winds was made by Dr. Alvin C. Graves, the Scientific Director of Operation Castle. Graves had total authority over detonating the weapon, above that of the military commander of Operation Castle. Graves appears in the widely available film of the earlier 1952 test "Ivy Mike", which examines the last-minute fallout decisions. The narrator, the western actor Reed Hadley, is filmed aboard the control ship in that film, showing the final conference. Hadley points out that 20,000 people live in the potential area of the fallout. He asks the control panel scientist if the test can be aborted and is told "yes", but it would ruin all their preparations in setting up timed measuring instruments. In Mike, the fallout correctly landed north of the inhabited area but, in the 1954 Bravo test, there was a large amount of wind shear, and the wind that was blowing north the day before the test steadily veered towards the east.
Castle Bravo
827611#0
Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of "Operation Castle". Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon. Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving Li, which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
Castle Bravo
12284919#0
The Mark 21 nuclear bomb was a United States nuclear gravity bomb first produced in 1955. It was based on the TX-21 "Shrimp" prototype that had been detonated during the Castle Bravo test in March 1954. While most of the Operation Castle tests were intended to evaluate weapons intended for immediate stockpile, or which were already available for use as part of the Emergency Capability Program, Castle Bravo was intended to test a design which would drastically reduce the size and costs of the first generation of air-droppable atomic weapons (the Mk 14, Mk 17 & Mk 24). At long, in diameter, and weighing , the Mk-21 was half the length and one-third the weight of the Mk-17/24 weapons it replaced. Its minimum yield was specified at four megatons.
Mark 21 nuclear bomb
2196648#19
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
Lithium hydride
827611#39
The publication of the Bravo fallout analysis was a militarily sensitive issue, with Joseph Rotblat possibly deducing the staging nature of the Castle Bravo device by studying the ratio and presence of tell-tale isotopes, namely uranium-237, present in the fallout. This information could potentially reveal the means by which megaton-yield nuclear devices achieve their yield. Soviet scientist Andrei Sakharov hit upon what the Soviet Union regarded as "Sakharov's third idea" during the month after the Castle Bravo test, the final piece of the puzzle being the idea that the compression of the secondary can be accomplished by the primary's X-rays before fusion began.
Castle Bravo
827611#5
The device was called SHRIMP and had the same basic configuration (radiation implosion) as the "Ivy Mike" wet device, except with a different type of fusion fuel. "SHRIMP" used lithium deuteride (LiD), which is solid at room temperature; "Ivy Mike" used cryogenic liquid deuterium (D), which required elaborate cooling equipment. "Castle Bravo" was the first test by the United States of a practical deliverable fusion bomb, even though the TX-21 as proof-tested in the Bravo event was not weaponized. The successful test rendered obsolete the cryogenic design used by "Ivy Mike" and its weaponized derivative, the "JUGHEAD", which was slated to be tested as the initial "Castle Yankee". It also used a 7075 aluminum 9.5 cm thick ballistic case. Aluminum was used to drastically reduce bomb's weight and simultaneously provided sufficient radiation confinement time to raise yield, a departure from the heavy stainless steel casing (304L or MIM 316L) employed by contemporary weapon-projects.
Castle Bravo
523973#13
The most notable event of "Operation Castle" was the "Castle Bravo" test. The dry fuel for "Bravo" was 40% Li-6 and 60% Li-7. Only the Li-6 was expected to breed tritium for the deuterium-tritium fusion reaction; the Li-7 was expected to be inert. Yet J. Carson Mark, the head of the Los Alamos Theoretical Design Division, had speculated that "Bravo" could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated. It was discovered, because of the unexpected larger yield, that the Li-7 in the device also undergoes breeding that produces tritium. In practice, "Bravo" exceeded expectations by 150%, yielding 15 Mt — about 1,000 times more powerful than the "Little Boy" weapon used on Hiroshima. "Castle Bravo" remains to this day, the largest detonation ever carried out anywhere by the United States, and the fifth largest H-bomb detonation in the world.
Operation Castle
2194699#0
Castle Yankee was the code name given to one of the tests in the Operation Castle series of American tests of thermonuclear bombs. It was originally intended as a test of a TX-16/EC-16 bomb, but the design became obsolete after the Castle Bravo test was successful. The test device was replaced with a TX-24/EC-24 bomb which was detonated on May 5, 1954, at Bikini Atoll.
It released energy equivalent to 13.5 megatons of TNT, the second-largest yield ever in a U.S. fusion weapon test.
Castle Yankee
827611#38
Castle Bravo had the greatest yield of any U.S. nuclear test, 15 Mt, though again, a substantial fraction came from fission. In the Teller–Ulam design, the fission and fusion stages were kept physically separate in a reflective cavity. The radiation from the exploding fission primary brought the fuel in the fusion secondary to critical density and pressure, setting off thermonuclear (fusion) chain reactions, which in turn set off a tertiary fissioning of the bomb's U fusion tamper and casing. Consequently, this type of bomb is also known as a "fission-fusion-fission" device. The Soviet researchers, led by Andrei Sakharov, developed and tested their first Teller–Ulam device in 1955.
Castle Bravo