Bomb Wind

After 52 months of studying atom-bomb damage to buildings in Hiroshima and Nagasaki, the Atomic Energy Commission and the Department of Defense summed up their findings for the benefit of U.S. builders. They had little encouraging advice to offer. The report did not deal with the damage by radiation (heat, gamma rays, etc.), considered only the blast, which affects a much larger area than the radiation. But the blast effects it described were awesome enough.

Shock Wave. When an atom bomb explodes above the ground (as it did at Nagasaki and Hiroshima), the air around it is heated tremendously. Its push to expand creates a shock wave that roars outward in all directions with enormous speed. At 1,000 ft. from "zero," the point directly beneath the bomb, the wind whooshes out at 800 m.p.h., faster than the speed of sound. Two miles away, it is still blowing at 70 m.p.h.

The bomb wind hits a building with a sudden shattering shock. Then it passes over it, the compressed air of the wave squeezing it from behind. Unless the building's doors and windows have blown inward, it may collapse at once under the compressive force.

The great wind blows for a second or so. Then comes a moment of stillness as in the eye of a hurricane. After that the wind reverses and blows back about half as fast, but a longer time, toward the center of explosion. If the building has been weakened by the first shock, it is likely to be totally destroyed by the reverse blast.

Flying Missiles. Well-constructed Japanese buildings, said AEC's engineers, are at least as bomb-resistant as their counterparts in the U.S. Some of the newer ones, built to meet an earthquake code, are stronger. But the bomb blast rocked them and twisted them, blew away their sides, crumpled their floors and caved in their roofs. Brick-walled buildings, common in the U.S., flew into bits, big steel-skeletoned factories of U.S. type collapsed into twisted tangles.

The report holds out little hope that any U.S. city would fare much better. The large windows of U.S. office buildings might relieve the stress on the skeleton by blowing in immediately--and slicing anyone near them to ribbons. The brick or cement-block walls would turn into murderous missiles.

To avoid being blown to rubble, the report suggests, U.S. buildings should be redesigned to meet the specifications of strict codes used in earthquake regions. At present most are designed to resist a wind pressure of 20 lbs. a sq. ft. To give reasonable security against an atom bomb explosion half a mile away, this should be raised to 90 lbs. a sq. ft. At times of atom danger, all windows should be made of wire-glass and lined with heavy wire mesh to catch large flying fragments.

The report suggests no defense at all against the heat of the bomb, holds out almost no hope for buildings less than half a mile from the zero point. And the recommendations it does make are based on an almost obsolete weapon--not the improved bombs already tested at Eniwetok, or the hydrogen bomb that is soon to come.

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