THE ATOM: From the Air

Almost two weeks behind schedule because of unfavorable winds, the U.S. this week fired its eighth hydrogen device—its first superbomb to be dropped from a plane. Estimated size of the big shot: 10 megatons, the equivalent of 10 million tons of TNT.

During predawn darkness in the mid-Pacific atomic proving grounds, the B-52 intercontinental jet bomber Barbara Grace roared upwards from Eniwetok Air Base, the big bomb in its belly. A fleet manned by 13,500 men stood 39 miles off target—Namu Atoll at the northwest edge of Bikini Atoll—while the big B-52 climbed to an altitude of 40,000 to 50,000 ft. Suddenly a fireball flared through the dark—silver-white, creamy-white, orange, red, boiling outward to a three-mile diameter at a speed of hundreds of miles per hour. Along the horizon spread a broad bank of dirty clouds of dust and moisture, merging upwards into the fireball to form the characteristic and by now famous mushroom cloud.

Two minutes and 43 seconds after the explosion, the shock wave rocked the fleet, roaring dully in men's eardrums for some 30 seconds. The mushroom rose high above dark bands of natural clouds, showing traces of brown and small brilliant pinpoints of light, tinctured cerise and pink by the dawn. Ten minutes later the cloud towered 80,000 to 90,000 ft. above the sea. In five more minutes it stood 100,000 ft. up. Flattening out, its spread covered 100 miles. Winds bore the fallout far from inhabited land, away across the empty ocean.

The big shot was the U.S.'s 67th atomic-type explosion, as against about 15 for Russia, three for Britain.