Baby Bombs

The Associated Press sent out a short item last week about baby atomic bombs now in the possession of the U.S. The bombs are small enough, said the A.P., to be carried by jet bombers, but are not necessarily less powerful than old-style A-bombs.

This information was said to have come from unidentified "officials." Whether official or not, the news was very likely true, to some extent at least. The heart of an atomic bomb is its fissionable material--something like 25 lbs. of plutonium or U-235. The rest might be largely eliminated by improved design.

The crude bombs dropped on Hiroshima and Nagasaki were rush jobs intended to be carried in a B29. There was little reason to keep their weight down, since the B-29s of the time could carry 20,000 lbs. from Saipan to the target. Long after Nagasaki, the weight of the first bombs leaked out. It was about 10,000 lbs.

Part of the weight was "low-order" (chemical) explosive to detonate the bomb by driving together its subcritical masses of uranium. Another part was the "tamper"--a casing of metal whose inertia kept the exploding bomb from expanding too rapidly, i.e., before the nuclear explosive had time to react.

Both these major parts could certainly be lightened. In the first bombs they were probably made heavy deliberately, just to keep on the safe side. It is possible, too, that radically different ways of detonating the bombs have been developed in the last five years of intensive effort. An efficient absorber of neutrons, for instance, might keep a large mass of uranium from exploding prematurely. When it is suddenly removed, the uranium would start reacting. Such a device would reduce or eliminate entirely the low-order explosive. Also, it may have been possible to speed up the nuclear reaction, thus making the tamper less necessary. Atomic bombs, like other bombs, will always weigh more than their explosive hearts, but presumably they need not weigh nearly 400 times as much.

It is obviously important to reduce the weight of the bombs as much as possible without too great loss of efficiency. Heavy bombs of the Hiroshima type can be dropped only from large, vulnerable aircraft directly over the target. Light bombs might be carried by small, fast, elusive jet bombers, or by rockets or other guided missiles launched from a safe distance.

This file is automatically generated by a robot program, so reader's discretion is required.