The basic concept of a bomb could hardly be simpler. A conventional bomb consists of some explosive material packed into a sturdy case with a fuze mechanism (yes, that's fuze, not fuse). The fuze mechanism has a triggering device -- typically a time-delay system, an impact sensor or a target-proximity sensor -- which sets the bomb off. When the trigger goes off, the fuze ignites the explosive material, resulting in an explosion. The extreme pressure and flying debris of the explosion destroys surrounding structures (see How Grenades Work for information on explosives and fuzes).

Photo courtesy U.S. Department of Defense
An F-15 Strike Eagle drops GBU-12 laser-guided smart bombs.

A "dumb bomb" is a bomb with only these elements, dropped from an airplane (such as the B-2 bomber). The bomb is considered "dumb" because it simply falls to the ground without actively steering itself. Needless to say, it's some feat hitting a target precisely with this type of weapon. A bomber might have to drop dozens, or even hundreds of dumb bombs to take out a target effectively.

"Smart bombs," by contrast, control their fall precisely in order to hit a designated target dead on. In this edition of HowStuffWorks, we'll find out how the major types of smart bomb accomplish this.