Skip navigationOf new weapons and nuclear genies



1. Who's got the bomb?

2. How nukes work

3. Bring forth the 4th generation

4. Never say "never"

5. An end to the search?


A chain reaction occurs when neutrons from fission strike another uranium or plutonium nucleus, causing another fission.
Courtesy University of Missouri-Rolla Student Chapter, American Nuclear Society


Meet the ol' reliables: fission 'n fusion
All nuclear bombs rely on energy from fission. Many also use fusion:
FISSION - splitting - powered first-generation nuclear weapons. You bombard heavy, unstable atoms like uranium with neutrons. When a uranium nucleus accepts another neutron, it splits into smaller atoms, releasing energy and more neutrons. Those neutrons go on to split other uranium atoms, causing a chain reaction.

Diagram shows that one fission (splitting of the nucleus) leads to another. Eventually (in nanoseconds, actually), the gathering energy blows the bomb apart, ending the chain reaction. (Fission, btw, also powers nuclear generating plants).

FUSION - combining - is used in second-generation nuclear weapons (and the sun, come to think of it). When nuclei of light atoms are squeezed close enough, they overcome their natural repulsion and join, or "fuse," making heavier atoms and releasing, you guessed it, gobs of energy, mainly as fast nucleons (neutrons and protons). Because it takes intense force to compress the nuclei, all fusion bombs are powered by a fission bomb, called the "primary" stage.

The possibility that other power sources could do the compressing motivates much of the search for fourth-generation nukes.

If nuclear weapons sound easy to make, they are -- at least conceptually. Bombard the right fuel with neutrons (or simply compress it), and stand back a few miles. Better yet, stand back a few miles, then start the reaction...

Generation, or degeneration?
First generation nuclear weapon: "Atomic" (fission) bombs destroyed Hiroshima and Nagasaki in 1945, ending World War II.

Second-generation: "Hydrogen" (fusion) bomb, the workhorses of U.S. and Russian arsenals. Uses a fission bomb to start the fusion reaction.

Third-generation: "X-ray laser" (directed-energy) and "neutron" (enhanced-radiation) weapons (see "Third-Generation..." in the bibliography). A bust. The laser didn't work, and the neutron bomb found no military use.

Fourth-generation: Anything not invented, especially fusion bombs started without fission, but not simply a modified existing weapon. Could use many physical principles; may not be possible or practical.

A bomb, complete with tail fins, at the back  of the table, with hundreds of parts laid out in front.
This exploded (heh heh) view shows all the parts you need to make this bomb - right in yer garage! Did they snarf those nifty tail fins from a '59 Cadillac? Sandia National Laboratories.

Specifics. We need some physical principles on these supposed "fourth-generation" weapons.












the why files


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