fy for Doomsday

Herman Kahn's ponderous shocker, On Thermonuclear War, frequently mentions a weapon whose purpose is to end all human life: the Doomsday Machine. Kahn discusses its political uses as calmly as if it were a bug killer, but he gives few technical details. In the latest Bulletin of the Atomic Scientists, Physicist W. H. Clark spells out some little-known facts about Doomsday Machines--and some of the more refined horrors that nuclear war could bring. Both the U.S. and Russia already can build near-Doomsday bombs, but far more disturbing is the fact that they are sufficiently inexpensive and simple to be built by smaller nations with an emerging atomic technology.

The detonator of a thermonuclear bomb is a fission bomb containing plutonium or uranium 235, and its explosion sets off the main charge of fusion material, which is essentially deuterium (heavy hydrogen). Fission detonators are expensive, but a single one can explode any amount of comparatively cheap fusion material. Result: the bigger the bomb, the cheaper it is in terms of explosive yield. Clark figures that a ten-megaton bomb costs somewhat more than $1,000,000, mostly for the detonator. But further increases in yield cost only about $5,000 per megaton, so that the price tag on a 100-megaton bomb is roughly $1,500,000. A 1,000-megaton bomb would cost $6,000,000. Once they acquired enough fission material, many middle-sized countries could fashion even bigger bombs and, by using certain techniques, produce near-Doomsday destruction and death by exploding comparatively few of them.

Among the techniques: >A nuclear bomb could be loaded on a submarine or barge and planted on the ocean bottom near the coast of a target country. Exploded under two miles of water (at the aggressor's will and from great distance), a 20,000-megaton bomb would stir up a wave whose crest would still be 100 feet high after it had traveled 200 miles. It would wash most coastlines bare and ride far inland.

>For better Doomsday effect, large bombs could be made as radioactive as possible. One way is to "salt" them with sodium, which becomes intensely radioactive when it absorbs neutrons. Clark figures that a 20,000-megaton bomb of this kind would contaminate 200,000 square miles (four times the area of New York State) so heavily that even people in basement shelters would surely die. But since the half life of radioactive sodium 24 is only 15 hours, the bomb's products would lose much of their punch before the wind could carry them around the earth. Thus, a sodium-salted bomb would not be a true Doomsday Machine.

> More deadly yet would be large fission-fusion-fission bombs whose outer blankets of cheap uranium 238 yield energy as well as deadly fission products. Clark believes that any nuclear power could easily destroy a nation with the close-range fallout effect from this type of bomb, but he thinks that the human race as a whole would be more resistant.

> Probably the most effective bomb in spreading worldwide death would be salted with cobalt, which absorbs neutrons and turns into radioactive cobalt 60. Since cobalt 60's half life is five years, it would be carried all over the earth before losing its activity. About 50,000 megatons of cobalt-salted bombs would theoretically provide enough long-lasting radioactivity to kill everyone on earth.

Despite the massive destructive potential of these bombs, Clark believes that not even such a Doomsday Machine--should any nation ever be suicidal enough to use one--would completely wipe out human life. In deep caves or far-underground shelters, enough people might find refuge to wait out the radioactivity and emerge to begin again. Concludes Physicist Clark: "The indications are that the human race will survive the H-bomb, though it will be a close thing. Until some more efficient process is discovered, extermination will require a major effort by one or both of the great powers. Lesser states will have to be content with destroying most people and making the rest miserable."

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