Twenty-Two Miles High

Japan's long-distance scientific atom-bomb watchers (TIME, March 12 et seq.) were convinced that a nuclear weapon fired by the U.S. July 3 over Bikini was carried by a rocket, not an airplane, and that it exploded at a height of at least 22 miles.

Kameo Ito, chief of the government's Yamagata meteorological observatory, bases his theory on a close study of the air waves from U.S. and Soviet tests. When a bomb is exploded on the ground or near it, says Ito, the shock waves spreading upward into the lower stratosphere are lengthened and delayed by air conditions there. Eventually they are refracted downward and reach microbarographs in Japan a few minutes behind the shorter waves that have passed directly through the lower atmosphere.

Tell-tale Pattern. The waves from earlier U.S. and Soviet tests followed this pattern. But during this summer's tests, Japan's microbarographs showed a difference. With each explosion (the U.S. has announced only one), the initial, shortwave phase decreased, indicating that the bombs were being exploded higher and higher in the atmosphere. On July 3, the Japanese picked up a wave pattern" that had almost no short waves. Ito thinks this proves that the explosion took place above 22 miles. If it did, Ito reasons, the bomb must have been carried by a rocket. No existing bomber can fly so high.

Testing weapons systems instead of isolated "nuclear devices" is one of the announced purposes of the U.S. tests at Bikini. One of the systems that needs testing most is the atom-armed antimissile rocket that both the U.S. and the U.S.S.R. are believed to be developing. To protect a target city from a long-range missile, this weapon must attack its quarry high above the atmosphere.

Unrestrained Fireball. Shooting it up to the proper height is not much of a problem, but no one knows how its nuclear warhead will behave when it is exploded in the near-vacuum of the upper atmosphere. With little air to resist its expansion, the unrestrained fireball may grow to enormous size. Atomic particles and radiation that are stopped by dense air may be flung far enough to do damage at a considerable distance.

If the U.S.'s July 3 test bomb was really exploded 22 miles above the earth, it should yield valuable information in another way too. One of the toughest problems for the designers of long-range ballistic missiles is "re-entry": i.e., how to get the missile's warhead down through the lower atmosphere at meteor speed without having it burn up like a meteor. If the July 3 test showed that a nuclear warhead achieves "good" effects on ground targets, even when exploded 20 miles above the surface, most of the re-entry problem will have been eliminated.

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