Why invent fusion bombs, if fission bombs were so powerful anyway?
Fission bombs produce their destructive energy by splitting atoms of uranium apart. This system works, however, soon after the initial explosion the uranium235 atoms would be so far apart (atomically speaking) that the reaction would cease as no free neutrons would hit other uranium atoms and keep the process going. Unlike fission bombs, fusion bombs (thermonuclear devices), produce energy by bonding together lighter atoms to make heavier ones. Unlike the fission process there is no limit on the amount of fusions that can occur. Thus, fusion bombs can be made with higher yields, and are therefore more destructive. As a very rough rule of thumb, a fusion bomb is around a thousand times more powerful, than an equivalently sized fission bomb. Fusion bombs need incredible hot temperatures to begin the reaction process. For this they use small fission devices within them.
