PURSERS HUD DEATH STARS 49
surements during the Cabra test was destroyed; hence its readings
could not be trusted.)
Can such a controversial device in fact be used today to shoot
down ICBM warheads? Perhaps. But an enemy could use a variety of
simple, inexpensive methods to nullify such weapons (for example, the
enemy could release millions of cheap decoys to fool radar, or spin its
warheads to disperse the X-rays, or emit a chemical coating to protect
against the X-ray beam). Or an enemy might simply mass-produce
warheads to penetrate a Star Wars defensive shield.
So a nuclear-powered X-ray laser today is impractical as a missile
defense system. But would it be possible to create a Death Star to use
against an approaching asteroid, or to annihilate an entire planet?
THE PHYSICS OF A DEATH STAR
Can weapons be created that could destroy an entire planet, as in Star
Wars? In theory, the answer is yes. There are several ways in which
they might be created.
First, there is no physical limit to the energy that can be released
by a hydrogen bomb. Here's how this works. (The precise outlines of
the hydrogen bomb are top secret and classified even today by the U.S.
government, but the broad outlines are well known.) A hydrogen
bomb is actually built in many stages. By properly stacking these
stages in sequence, one could produce a nuclear bomb of almost arbitrary magnitude.
The first stage is a standard fission bomb, using the power of uranium-235 to release a burst of X-rays, as was done in the Hiroshima
bomb. In the fraction of a second before the blast from the atomic
bomb blows everything apart, the expanding sphere of X-rays outraces
the blast (since it travels at the speed of light) and is then refocused
onto a container of lithium deuteride, the active substance of a hydrogen bomb. (Precisely how this is done is still classified.) The X-rays
striking the lithium deuteride causes it to collapse and heat up to millions of degrees, causing a second explosion, much larger than the
surements during the Cabra test was destroyed; hence its readings
could not be trusted.)
Can such a controversial device in fact be used today to shoot
down ICBM warheads? Perhaps. But an enemy could use a variety of
simple, inexpensive methods to nullify such weapons (for example, the
enemy could release millions of cheap decoys to fool radar, or spin its
warheads to disperse the X-rays, or emit a chemical coating to protect
against the X-ray beam). Or an enemy might simply mass-produce
warheads to penetrate a Star Wars defensive shield.
So a nuclear-powered X-ray laser today is impractical as a missile
defense system. But would it be possible to create a Death Star to use
against an approaching asteroid, or to annihilate an entire planet?
THE PHYSICS OF A DEATH STAR
Can weapons be created that could destroy an entire planet, as in Star
Wars? In theory, the answer is yes. There are several ways in which
they might be created.
First, there is no physical limit to the energy that can be released
by a hydrogen bomb. Here's how this works. (The precise outlines of
the hydrogen bomb are top secret and classified even today by the U.S.
government, but the broad outlines are well known.) A hydrogen
bomb is actually built in many stages. By properly stacking these
stages in sequence, one could produce a nuclear bomb of almost arbitrary magnitude.
The first stage is a standard fission bomb, using the power of uranium-235 to release a burst of X-rays, as was done in the Hiroshima
bomb. In the fraction of a second before the blast from the atomic
bomb blows everything apart, the expanding sphere of X-rays outraces
the blast (since it travels at the speed of light) and is then refocused
onto a container of lithium deuteride, the active substance of a hydrogen bomb. (Precisely how this is done is still classified.) The X-rays
striking the lithium deuteride causes it to collapse and heat up to millions of degrees, causing a second explosion, much larger than the