Above: Ivy-Mike shot, Eniwetok Atoll, 1 November 1952 (local time). It was three stage thermonuclear surface burst on Elugelab Island (which was erased, leaving a 1 mile wide water filled crater which sloped down to a depth of 175 feet below the original island surface or 164 feet below water) with a total energy yield of 10.4 Mt (1950s nuclear weapons were far bigger than anything America has in its present stockpile, which is dominated by 3,030 small 100 kt W76/Mk-4MIRV missile warheads each of yield of which 1,712 are active in the stockpile, which are far more efficient than heavy, bulky megaton bombs since the static blast overpressure damage radii only increase with the cube root of the energy release). Thermal radiation is reduced in surface bursts because of the low elevation angle (so intervening obstacles shield it most of it, and even if the blast later damages them, dust clouds are produced which shield it), and the conical cone of debris gauged out of the crater within milliseconds absorbs 7.5-9.2 % of the total initial fireball energy to create melted droplets of fallout in surface bursts of 1 kt-100 Mt (these numbers are from Dr Carl F. Miller's 1963 SRI Report, Fallout and Radiological Countermeasures, vol. 1).
Above: the Castle-Bravo test, a 14.8 Mt at Bikini Atoll surface burst on an artificial island or causeway on the reef, built from coral sand dredged up from the lagoon near Namu Island. Notice the thermal flash smoking of the stems of palm trees before the blast wave arrives. This test produced the first major fallout controversy because of the mean direction of the wind veered within half an hour after the explosion. The fallout hotline should have been to the north east, but shifted to due east. This meant it contaminated people on Rongelap Atoll and several others, plus the crew of a Japanese tuna trawler which was just north of Rongelap. Much of the controversy occurred because the U.S. Atomic Energy Commission correctly announced on 11 March that the people did not have any beta radiation burns. This was widely reported, then the first cases of beta radiation burns to the skin showed up on 14 March, and cases continued to appear for the next two weeks because it is a delayed response. The U.S. Atomic Energy Commission only issued a reasonably complete report on the test effects on 15 February 1955, nearly a year later, by which time political damage had been done by media fear-mongering.)
Above: the first Chinese thermonuclear test, Lop Nur, 17 June 1967, a 3.3 Mt thermonuclear air burst detonated at an altitude of 2,960 m.
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