Page:Operation Crossroads 1946.pdf/92



Figure 22. "Dave's Dream," the B-29 from which the CROSSROADS, ABLE weapon was dropped.

All other air operations within 500 nmi (927 km) had been suspended 12 hours before the shot.

Observers included Congressmen, the President's Evaluation Commission, the Joint Chiefs of Staff (JCS) Evaluation Board, United Nations representatives, and media correspondents. The live run was made at 28,000 feet (8.5 km). The bomb was released at 0859 and detonated with a yield of 23 KT 15 seconds before 0900, 1,500 to 2,000 feet (457 to 610 meters) west of the planned surface zero (Figure 23).

An Army doctor trained as a radiological safety (radsafe) monitor made the following observation from a PBM aircraft 20 nmi (37 km) away (Reference A.2, p. 55):

"At 20 miles it gave us no sound or flash or shock wave.... Then, suddenly we saw it -- a huge column of clouds, dense, white, boiling up through the strata-cumulus, looking much like any other thunderhead but climbing as no storm cloud ever could. It climbed rapidly to 30,000 or 40,000 feet, growing a tawny-pink from oxides of nitrogen, and seemed to be reaching out in an expanding umbrella overhead.... For minutes the cloud stood solid and impressive, like some gigantic monument over Bikini. Then finally the shearing of the winds at different altitudes began to tear it up into a weird zigzag pattern."

An aerial view of the cloud from the southeast is shown in Figure 24.

The radiological danger sector (radex) designed for aircraft at 0730 on the shot day predicted the downwind danger area to be between 325° clockwise

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