Historical Fallout

Q. Mr. Greenglass, addressing yourself to the Government's Exhibit 8, if you please, is that a cross section of the atomic bomb?

A. It is.

Q. That you gave to Mr. Rosenberg?

A. It is.

As a result of Manhattan Project Machinist David Greenglass's secret testimony in 1951, Julius and Ethel Rosenberg were executed for giving the Russians what the U.S. prosecutor described as a sketch of the 1945 Nagasaki "Fat Man" atomic bomb (see cut). For purportedly aiding the Rosenbergs, Morton Sobell got 30 years. But was the sketch substantially accurate?

The odds favor a yes answer. But if it is no, Prisoner Sobell may conceivably succeed in his current bid for freedom. Indeed, two ex-Manhattan Project scientists are prepared to back Sobell's claim that the sketch was false, inaccurate and incomplete. Whatever the outcome, the case has already supplied a crucial bit of historical fallout. Last week a Manhattan federal court released the long-impounded alleged sketch of the Nagasaki bomb--the first time it has ever been seen in public.

To nuclear sophisticates, the sketch was actually old hat. Today, almost any bright high school physics student understands the basic principles of the Nagasaki bomb.

In order for such a bomb to explode, the fissionable core material of plutonium (sketch point E) must be raised to a supercritical mass, the point where sufficient neutrons are released and react with the core material to sustain violent nuclear reactions. In the implosion bomb shown in the sketch, shaped charges of high explosives (B) are simultaneously triggered by detonators (A), the force of the explosions being directed inward, rapidly compressing the plutonium around a beryllium neutron source (D). In less than a millionth of a second, the supercritical mass explodes.

This was basically the description that Greenglass gave in his impounded testimony. Whether or not such knowledge was vital to Russian development of the bomb remains speculative. In any case, the same general principles are used in modern tactical atomic weapons, even though engineering refinements have gone drastically beyond the crude "Fat Man" version of 21 years ago.

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