NEVADA TEST SITE
An experimental device by Livermore Laboratory, was fired from a a 700 foot tower in Yucca Flat at 5:30 a.m. today. It was the fifteenth full scale nuclear detonation in the summer 1957 series.
At about 4:45 a.m. the shot time was postponed from the scheduled 5 a.m. until 5:30 a.m. to provide time for balloon runs and aircraft checks to determine wind speeds and directions above the Test Site.
On the basis of early data, the Test Director reported that the yield was in the designed range, or in a range of about twice nominal.
The explosion was visually of interest to observers because of the continuing intensity and visibility of the blue light caused by ionization of nitrogen surrounding tthe fireball. This resulted from the darkness existing at shot time.
The cloud rose above 35,000 feet, penetrating slightly through the tropopause. It was the opinion of observers that there was less dust blasted up from the desert and a less stocky and dirty-appearing cloud stem than has accompanied lower yield shots fired from 500-foot towers. Cloud tracking aircraft reported at 6:30 a.m. that the cloud top was being blown generally toward the east at about 48 knots, with lower segments moving more slowly in a more southeasterly direction. There was considerable variance in wind direction, providing desired shear which should result in fairly wide diffusion of the cloud segments, reducing the intemsity of fallout at any one point.
The blast was quite strong in the observer area and was measured at slightly under 16 milibars at the Control Point, where it was felt as a sharp blow and heard as a sharp report, followed by rumblings and echoes from the hills. Bishop and Inyokern reported hearing rumbles and bangs, and St. George and Tonopah reported rumbles.
There were about 30 experiments on the sequence timer. Thirty-two U.S. Air Force and nine Navy aircraft participated with effects, training, and technical support flight. Five light Army aircraft and 40 helicopters were used in a post-shot exercise.
As part of the civil effects program, prototypes of mass shelters were subjected to effects experiments for the French and German Governments.
Pre-shot prediction that there probably would be fairly heavy fallout immediately south and southeast of the zero point caused changes in the Desert Rock Army maneuver. The trenches at 4,500 yards were not used by military observers or troops of the "human research" project, the former observing from a point some eight miles distant and the latter simply observing from a point near News Nob. The "human research" project may be conducted on the next shot.
Troops scheduled to participate in the post-shot assault maneuver observed from from an alternate area 8,500 yards southwest of zero point, instead of southeast.
Fire chiefs from Los Angeles, Bakersfield and San Diego, California, and Las Vegas were scheduled to test methods for decontaminating structures and areas at about three hours after the shot.