Finally, what is the destructive difference between a hydrogen bomb and an atomic bomb? Is there anything more destructive than a hydrogen bomb?
The atomic bombs dropped on Japan were fission weapons, one was a gun type weapon (the one dropped on Hiroshima), and one was an implosion type weapon. The bomb dropped on Hiroshima, named Little Boy, yielded between 12-18 Kilotons. The bomb dropped on Nagasaki, named Fat Man, yielded approximately 21 Kilotons. Modern nuclear warheads are fusion weapons also known as hydrogen bombs. The largest such weapon ever set off was the 50 Megaton, Tsar Bomba Soviet three stage fission-fusion-fission design which was detonated October 30, 1961. At this point there is no weapon more destructive than present day fission weapon designs. I highly recommend Carey Sublettes site at http://www.fas.org/nuke/hew/ for more information on nuclear weapons.
