In modern usage, a
missile is a self-propelled
precision-guided munition system, as opposed to an unguided self-propelled munition, referred to as a
rocket (although these too can also be
guided). Missiles have four system components: targeting and/or
missile guidance, flight system, engine, and warhead. Missiles come in types adapted for different purposes:
surface-to-surface and
air-to-surface missiles (
ballistic,
cruise,
anti-ship,
anti-tank, etc.),
surface-to-air missiles (and
anti-ballistic),
air-to-air missiles, and
anti-satellite weapons. All known existing missiles are designed to be propelled during powered flight by chemical reactions inside a
rocket engine,
jet engine, or other type of engine. Non-self-propelled airborne
explosive devices are generally referred to as
shells and usually have a shorter range than missiles.