June 24, 1957

The following was released at 7:20 a.m. Monday, June 24:

"Priscilla, scheduled in the current atomic test series as a military effects shot, was fired this morning at 6:30 a.m. It was the fifth shot in the series.

"The experimental device was developed by Los Alamos Scientific Laboratory. It was suspended at a height of 700 feet from a helium-filled balloon 67 feet in diameter.

"There were approximately 81 diagnostic and effects experiments on the sequence timer, 33 major military effects projects, and an extensive test of shelters by the Federal Civil Defense Administration. Included in the military effects tests was an experiment involving over 900 pigs in which bio-medical and fabrics studies were made. A small number of rabbits and dogs also were used in military and civil effects tests.

"Other experiments were conducted as previously announced. Approximately 35 U.S. Air Force and U.S. Navy aircraft participated.

"Approximately 1,000 military observers viewed the detonation from trenches about 4,500 yards from ground zero. The observers were drawn from all the military services and from major commands throughout the country.

"The blast was felt very sharply at the Control Point, over 14 miles from ground zero. Swinging interior doors at the entranceways were torn from their hinges, and interion walls were cracked at one entrance. The strong first blast was followed by sustained rumblings. A strong blast was felt at Camp Mercury and at Indian Springs Air Gorce Base. It was heard as a rumble in Tonopah and Reno {Nevada}, and Bishop {California}. Stratospheric reflection of the sound wave resulted in its being heard as a rumble and bang in Inyokern, California.

"Observers at the Control Point reported that the flash was extremely bright, despite the full sunlight. The mushroom top of the cloud rose rapidly to well above 40,000 feet, reaching the lower edge of the tropopause. Following it, a heavy pillar of dust was lifted, composed of the talcum-powder like dust from the surgace of Frenchman Flat dry lake. It formed a mushroom-shaped cloud atop the stem, creating the unusual effect of a mushroom stem and cloud with a second separated cloud lifting above them.

"It was estimated that there was little radioactivity in the stem, which will in any case settle back on the site. As forecast from wind direction data throughout the night, the top cloud was being blown slightly north of due east {into 70 degrees} from Frenchman Flat, moving at a speed of about 22 knots. The top cloud extends from above 40,000 feet down to about 30,000 feet. Only light fallout readings are anticipated at the distances of Highway 93 and any further distances toward Utah."

[B-25 Cloud Tracker]

[Warning on Flash]