TOM NICHOLS: About Those Bombs.

First, let’s be clear about what kind of bomb the Norks have developed. A nuclear bomb relies on splitting atoms of uranium and plutonium through the process of nuclear fission to produce an explosion. This is the kind of bomb the North Koreans tested in 2006 and the only kind they have.

That’s plenty bad, but not as bad as the more powerful thermonuclear bomb uses that fission explosion to fuse hydrogen atoms together (which is why it’s also called a fusion bomb) to produce a much, much more devastating explosion. This is the bomb used in the nuclear arsenals of the advanced nuclear powers, and while the North Koreans claim to have tested one, it’s unlikely.

A bomb without a ride to its destination is just a really dangerous paperweight, and the North Koreans have made progress on testing an ICBM, the acronym for an inter-continental ballistic missile, a rocket that throws a warhead—the bomb—into space, after which that warhead falls back to earth at many times the speed of sound.

This is different from short-range rockets or artillery, or even Saddam Hussein’s infamous SCUDs, which are fired at short range and go relatively smaller distances. Those are easy to make; Saddam’s missiles were of 1960s vintage. ICBMs are a different game entirely. ICBMs are like the rockets that sent men to the moon, capable of traveling huge distances and landing close to a designated target.

A crude nuclear bomb isn’t that hard to make, if you have enough uranium and don’t care how big it is. (The first nuclear bomb was the size of a small automobile and had to be shoved out of an airplane in 1945.) A nuclear ICBM is a lot tougher to manufacture, because a small, reliable bomb is a lot more complicated, and placing that warhead on top of a space-capable vehicle is yet more of a challenge.

This is because a nuclear ICBM requires a small enough warhead to fit on top of a big, wobbly missile and withstand the pressures of launch, traversing space, and re-entry into the atmosphere. Nuclear bombs are not hand grenades; they are delicate and finely engineered weapons that will not explode if their machinery is destroyed while plunging to earth at Mach 20.

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