Physical Cosmology

How do hydrogen bombs work?
Answered by Craig C. Freudenrich and Discovery Channel
  • Craig C. Freudenrich

    Craig C. Freudenrich

  • Discovery Channel

    Discovery Channel

  1. Hydrogen bombs, or H-bombs, never were used in World War II, even though the idea for them was introduced before 1940 [source: CBS News]. Hydrogen bombs use the process of nuclear fusion -- or fusing instead of splitting nuclei -- to create enormous amounts of heat and radiation explosively. The process of fusion requires that hydrogen isotopes be squeezed together under high temperatures and pressures to fuse into helium, which releases heat, neutrons and energy.

    There are some challenges to creating fusion in a bomb. First, the hydrogen isotopes deuterium and tritium are gases, which are hard to store. Bomb makers instead use solid lithium-deuterate because it is easy to store, does not radioactively decay at room temperature and can produce both deuterium and tritium under high temperatures and pressures. Second, the bomb must have high temperatures and pressures for fusion to occur; this requires a fission reaction. A hydrogen bomb is essentially two types of bombs -- an implosion-type fission bomb and a fusion bomb -- in one casing. This design is named a Teller-Ulam bomb after the designers, Edward Teller and Stanislaw Ulam. The major inside components are:

    • Fission bomb -- a sphere containing a uranium-235/plutonium-239 core (fissionable material), enveloped by a uranium-238 tamper that is surrounded by chemical explosives. A tamper makes a fission process more efficient by expanding when heated and exerting pressure on the fission process. It also reflects neutrons back into the fission process.
    • Fusion bomb -- cylinder with a core rod of plutonium-239 surrounded by lithium-deuterate fuel and a uranium-238 tamper
    • Polystyrene foam -- fills the empty space in the casing

    The explosives in the fission bomb go off, which compresses the fission fuel and initiates fission. Fission produces high heat, X-rays and neutrons. The X-rays heat the foam and tamper around the fusion bomb. The heated tamper and X-rays exert high pressure and temperatures on the fusion capsule, which squeezes the fuel and initiates fission in the plutonium rod. The neutrons from the fission of the rod combine with the lithium-deuterate to produce tritium and deuterium. The high temperatures and pressures cause the deuterium and tritium to fuse, which produces helium, high heat, X-rays and neutrons. The bomb explodes and releases heat, X-rays and neutrons. All of these events occur in just billionths of a second and release 700 times more energy than the atomic bombs dropped on Hiroshima and Nagasaki, Japan.

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  2. Hydrogen bombs use fusion to create an enormous explosion. First, the bomb has to create enough energy to overcome the electromagnetic force that causes hydrogen nuclei to repel each other. To do this, the bomb has two stages. The first stage is a fission bomb. Fission is the act of splitting a nucleus, which also creates a tremendous amount of energy. This energy becomes heat, which transfers to liquid deuterium -- an isotope of hydrogen. The enormous amount of heat fuses the hydrogen isotopes together to create helium and releases even more energy -- the second stage of the hydrogen bomb. This fusion process happens in the core of the Sun and is what provides us with the energy we need to survive.

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