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Admiral Blandy and his wife slice into a cake labeled Operation Crossroads, and shaped like a mushroom cloud, while Admiral Frank J. Lowry looks on, November 7, 1946.
Admiral Blandy and his wife slice into an Operation Crossroads cake shaped like Baker's radioactive geyser, while Admiral Frank J. Lowry looks on, November 7, 1946.

Cockpit opening

38.1 cm (15.0 in) -- 71.1 cm (28.0 in) -- 198.1 cm (78.0 in) My black Galasport

39.4 cm (15.5 in) -- 73.7 cm (29.0 in) -- 203.2 cm (80.0 in) My blue Fox

39.0 cm (15.4 in) -- 74.0 cm (29.1 in) All new Galasports

45.0 cm (17.7 in) -- 78.0 cm (30.7 in) Fluid Donsa

38.1 cm (15.0 in) -- 67.3 cm (26.5 in) -- 188.0 cm (74.0 in) Mirage

Boat length

2.390 m (7.84 ft) Dagger CFS

2.540 m (8.33 ft) Habitat 80

3.645 m (11.96 ft) My black Galasport

3.594 m (11.79 ft) My blue Fox

4.000 m (13.123 ft) Mirage

Wausau Whitewater Park 44.957485, -89.633041

√4 = 2


Qiantang River Tidal Bore 30°16′45″N 120°23′15″E / 30.27923°N 120.387382°E / 30.27923; 120.387382

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Portrait of author Bi Feiyu in his Nanjing, China, home. Picture taken with permission of the subject


jump to the real thing ->

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Physical effects of the bomb

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After being selected in April 1945, Hiroshima was spared conventional bombing to serve as a pristine target, where the effects of a nuclear bomb on an undamaged city could be observed.[1] While damage could be studied later, the energy yield of the untested Little Boy design could be determined only at the moment of detonation, using instruments dropped by parachute from a plane flying in formation with the one that dropped the bomb. Radio-transmitted data from these instruments indicated a yield of about 15 kilotons.[2]

Comparing this yield to the observed damage produced a rule of thumb called the 5 psi lethal area rule. The number of immediate fatalities will approximately equal the number of people inside the area where the shock wave carries an overpressure of 5 psi or greater.[3] At Hiroshima, that area was 3.5 kilometres (2.2 mi) in diameter.[4]

The damage came from three main effects: blast, fire, and radiation.[5]

Blast

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The blast from a nuclear bomb is the result of X-ray-heated air (the fireball) sending a shock/pressure wave in all directions at a velocity greater than the speed of sound (aka, the "Mach-Stem"),[6] analogous to thunder generated by lightning. Our knowledge about urban blast destruction is based largely on studies of Little Boy at Hiroshima. Nagasaki buildings suffered similar damage at similar distances, but the Nagasaki bomb detonated 3.2 kilometres (2.0 mi) from the city center over hilly terrain that was partially bare of buildings.[7]

Frame house in 1953 nuclear test, 5 psi overpressure

In Hiroshima almost everything within 1.6 kilometres (1.0 mi) of the point directly under the explosion was completely destroyed, except for about 50 heavily reinforced, earthquake-resistant concrete buildings, only the shells of which remained standing. Most were completely gutted, with their windows, doors, sashes, and frames ripped out.[8] The perimeter of severe blast damage approximately followed the 5 psi contour at 1.8 kilometres (1.1 mi).

Later test explosions of nuclear weapons with houses and other test structures nearby confirmed the 5 psi overpressure threshold. Ordinary urban buildings experiencing it will be crushed, toppled, or gutted by the force of air pressure. The picture at right shows the effects of a nuclear-bomb-generated 5 psi pressure wave on a test structure in Nevada in 1953.[9]

A major effect of this kind of structural damage was that it created fuel for fires that were started simultaneously throughout the severe destruction region.

Fire

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The first effect of the explosion was blinding light, accompanied by radiant heat from the fireball. The Hiroshima fireball was 370 metres (1,200 ft) in diameter, with a surface temperature of 6,000 °C (10,830 °F).[10] Near ground zero, everything flammable burst into flame. One famous, anonymous Hiroshima victim, sitting on stone steps 260 metres (850 ft) from the hypocenter, left only a shadow, having absorbed the fireball heat that permanently bleached the surrounding stone.[11] Simultaneous fires were started throughout the blast-damaged area by fireball heat and by overturned stoves and furnaces, electrical shorts, etc. Twenty minutes after the detonation, these fires had merged into a firestorm, pulling in surface air from all directions to feed an inferno which consumed everything flammable.[12]

Hiroshima blast and fire damage, U.S. Strategic Bombing Survey map

The Hiroshima firestorm was roughly 3.2 kilometres (2.0 mi) in diameter, corresponding closely to the severe blast damage zone. (See the USSBS[13] map, right.) Blast-damaged buildings provided fuel for the fire. Structural lumber and furniture were splintered and scattered about. Debris-choked roads obstructed fire fighters. Broken gas pipes fueled the fire, and broken water pipes rendered hydrants useless.[12] At Nagasaki, the fires failed to merge into a single firestorm, and the fire-damaged area was only one fourth as great as at Hiroshmia, due in part to a southwest wind that pushed the fires away from the city.[14]

As the map shows, the Hiroshima firestorm jumped natural firebreaks (river channels), as well as prepared firebreaks. The spread of fire stopped only when it reached the edge of the blast-damaged area, encountering less available fuel.[15]

Accurate casualty figures are impossible to determine, because many victims were cremated by the firestorm, along with all record of their existence. The Manhattan Project report on Hiroshima estimated that 60% of immediate deaths were caused by fire, but with the caveat that "many persons near the center of explosion suffered fatal injuries from more than one of the bomb effects."[16] In particular, many fire victims also received lethal doses of nuclear radiation.

Radiation

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Local fallout is dust and ash from a bomb crater, contaminated with radioactive fission products. It falls to earth downwind of the crater and can produce, with radiation alone, a lethal area much larger than that from blast and fire. With an air burst, the fission products rise into the stratosphere, where they dissipate and become part of the global environment. Because Little Boy was an air burst 580 metres (1,900 ft) above the ground, there was no bomb crater and no local radioactive fallout.[17]

However, a burst of intense neutron and gamma radiation came directly from the fireball. Its lethal radius was 1.3 kilometres (0.8 mi),[4] covering about half of the firestorm area. An estimated 30% of immediate fatalities were people who received lethal doses of this direct radiation, but died in the firestorm before their radiation injuries would have become apparent. Over 6,000 people survived the blast and fire, but died of radiation injuries.[16] Among injured survivors, 30% had radiation injuries[18] from which they recovered, but with a lifelong increase in cancer risk.[19] To date, no radiation-related evidence of heritable diseases has been observed among the survivors' children.[20][21][22]

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  1. ^ Groves 1962, p. 267, "To enable us to assess accurately the effects of the [nuclear] bomb, the targets should not have been previously damaged by air raids." Four cities were chosen, including Hiroshima and Kyoto. War Secretary Stimson vetoed Kyoto, and Nagasaki was substituted. p. 275, "When our target cities were first selected, an order was sent to the Army Air Force in Guam not to bomb them without special authority from the War Department.".
  2. ^ Malik 1985, p. 1.
  3. ^ Glasstone 1962, p. 629.
  4. ^ a b Glasstone & Dolan 1977, p. Nuclear Bomb Effects Computer.
  5. ^ Glasstone & Dolan 1977, p. 1.
  6. ^ Diacon 1984, p. 18.
  7. ^ Glasstone & Dolan 1977, pp. 300, 301.
  8. ^ The Atomic Bombings of Hiroshima and Nagasaki, 1946, p. 14.
  9. ^ Glasstone & Dolan 1977, p. 179.
  10. ^ Nuclear Weapon Thermal Effects 1998.
  11. ^ Human Shadow Etched in Stone.
  12. ^ a b Glasstone & Dolan 1977, pp. 300–304.
  13. ^ D'Olier 1946, pp. 22–25.
  14. ^ Glasstone & Dolan 1977, p. 304.
  15. ^ The Atomic Bombings of Hiroshima and Nagasaki, 1946, pp. 21–23.
  16. ^ a b The Atomic Bombings of Hiroshima and Nagasaki, 1946, p. 21.
  17. ^ Glasstone & Dolan 1977, p. 409 "An air burst, by definition, is one taking place at such a height above the earth that no appreciable quantities of surface material are taken up into the fireball. . . the deposition of early fallout from an air burst will generally not be significant. An air burst, however, may produce some induced radioactive contamination in the general vicinity of ground zero as a result of neutron capture by elements in the soil." p. 36, "at Hiroshima . . . injuries due to fallout were completely absent.".
  18. ^ Glasstone & Dolan 1977, pp. 545, 546.
  19. ^ Richardson RR 2009.
  20. ^ Genetic Effects.
  21. ^ Izumi BJC 2003.
  22. ^ Izumi IJC 2003.

References

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march 1

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Operation Crossroads

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Baker, the underwater detonation of Operation Crossroads
Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. It was the first nuclear weapon test since Trinity in July 1945, and the first detonation of a nuclear device since the atomic bombing of Nagasaki on August 9, 1945. Its purpose was to investigate the effect of nuclear weapons on naval ships. The Crossroads tests were the first nuclear tests to be publicly announced beforehand and observed by an invited audience, including a large press corps. They were conducted by Joint Army/Navy Task Force One, headed by Vice Admiral William H. P. Blandy, rather than by the Manhattan Project, which had developed nuclear weapons during World War II. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki. The second of the two detonations, the underwater Baker shot, demonstrated, for the first time, the problem of radioactive contamination from "fallout." (Full article...)
  • This is my first nomination, so I am not sure how to proceed. I count a possible 4 points, since I am not aware of any TFA about nuclear weapons or nuclear weapons tests. At least half the article is my work. The relevant date, which would be worth only 1 point anyway, would be July 1, the 68th anniversary of the first detonation. March 1 is the 60th anniversary of the first Bikini test after Crossroads, and the test that ruined the atoll forever (that date is mentioned in passing in the article). However, I am nominating it for a non-specific date in hopes of speeding up the process.

blurb

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Baker, the underwater detonation of Operation Crossroads

Operation Crossroads was a series of two nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear detonations after World War II, and the first ever to be publicly announced beforehand and observed by an invited audience, including a large press corps. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons, each with a yield of 23 kt (96 TJ). The first test, Able, was an air burst that sank five ships and demonstrated the survivability of ships located more than one kilometer from the explosion. The second test, Baker, was an underwater explosion (pictured), which effectively destroyed the entire target fleet with radioactive contamination. It was the first case of immediate, concentrated radioactive fallout from a nuclear explosion. The fallout from Baker and subsequent Bikini tests still renders Bikini uninhabitable. Glenn Seaborg, the longest-serving chairman of the U.S. Atomic Energy Commission, called Baker "the world's first nuclear disaster." (Full article...)

Recently featured: Julianne Moore – William Burges – Frank's Cock

investigating and demonstrating the effect of nuclear weapons on naval ships.


Christianity Timeline - First Century

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