Missile

A missile is, broadly, a projectile, that is, something thrown or otherwise
propelled.

Missiles can range from a rock thrown from a slingshot through a crossbow
bolt to a Minuteman III intercontinental ballistic missile with multiple
nuclear warheads. The largest missiles currently deployed represent the most
destructive weapons ever made.

Rocket powered missiles are known simply as rockets.

Missiles are often used in warfare as a means of delivering destructive
force (usually a warhead) upon a target. Sometimes missiles are used to
deliver other payloads. For example in the Gulf War cruise missiles were
used to deliver reels of carbon filament to electricity stations and
switches, effectively disabling them by forming short circuits.

Missiles with no ability to maneuver are called ballistic missiles (because
their motion is governed by the laws of ballistics). Whilst quite a wide
term, unqualified use of the term ballistic missile is likely to mean an
initially rocket powered medium- to long-range missile; classically the ICBM.

Guided Missiles

Missiles that have the ability to maneuver can be guided, known as guided
missiles. There are 3 key components:

   * tracking
   * guidance
   * flight

A tracking system locates the missile's target. This can be either a human
gunner aiming a sight on the target (remotely from the missile) or an
automatic tracker. Automatic trackers use radiation emanating from the
target. Passive automatic trackers use the target's inherent radiation,
usually heat or light, but missiles designed to attack Command and Control
posts may use radio waves. Active automatic trackers rely on the target
being illuminated by radiation. The target can be "painted" with light (or
infra-red) or radio waves which can be detected by the missile. The
radiation for the painting can originate in the missile or from a remote
station (for example, a hilltop gunner can illuminate a target with a laser
device and this can be used to direct an air launched guided missile).

A guidance system takes data from the missile's tracking system and flight
system and computes a flight path for the missile designed to intercept the
target. It produces commands for the flight system.

The flight system causes the missile to maneuver. There are two main
systems: vectored thrust (for missiles that are powered throughout the
guidance phase of their flight) and aerodynamic maneuver (wings, fins, etc).

There are some similarities between guided missiles and guided bombs. A
guided bomb is unpowered and dropped from an aircraft, and uses aerodynamic
fins for maneuver.