about half the power of the weapon which destroyed h hoshima at end of world war ii. a hydrogen bomb which has never been used in war but tested in the pacific in the 1950s would be 50 to 100 times more powerful. whatever kind of device was definited. the greatest mystery about north korean nuclear weapons is whwhher they have capability to launch one against the united states. north korea has a missile capable of reaching that far, but it has never been tested. to be on the safe side, the u.s. keeps its missile defense system which officials say is capable of shooting down a small number of north korean missiles on constant alert. north korea seems to specialize in nasty surprises. u.s. intelligence expected but had no warning it would