For: Guided Missile

A missile (see also pronunciation differences) is a self-propelled, explosive projectile used as a weapon towards a target.

Missiles are typically propelled by rockets, but other engines such as ramjet, turbojet and turbofan engines can also be used.

Etymology

The word missile comes from the Latin verb mittere, literally meaning "to send".

In common military parlance, the word missile describes a powered, guided munition, whilst the word "rocket" describes an powered, unguided munition. A common further sub-division is to consider ballistic missile to mean a munition that follows a ballistic trajectory and cruise missile to describe a munition that generates lift. Guided missiles have three key system components:

• targeting
• guidance
• flight system

Missiles may be targeted in a number of ways. The most common method is to use some form of radiation, such as infra-red, lasers or radio waves, to guide the missile onto its target. This radiation may emanate from the target (such as the heat of an engine or the radio waves from an enemy radar), it may be provided by the missile itself (such as a radar) or it may be provided by a friendly third party (such as the radar of the lauch vehicle/platform, or a laser designator operated by friendly infantry). The first two are often known as fire and forget as they need no further support or control from the launch vehicle/platform in order to function. Another method is to use a TV camera - using either visible light or infra-red - in order to see the target. The picture may be used either by a human operator who steers the missile onto its target, or by a computer doing much the same job. Many missiles use a combination of two or more of the above methods, to improve accuracy and the chances of a successful engagement.

Another method is to target the missile by knowing the location of the target, and using a guidance system such as INS, TERCOM or GPS. This guidance system guides the missile by knowing the missile's current position and the position of the target, and then calculating a course between them. This job can also be performed somewhat crudely by a human operator who can see the target and the missile, and guides it using either cable or radio based remote-control.

Whether a guided missile uses a targeting system, a guidance system or both, it needs a flight system. The flight system uses the data from the targeting or guidance system to manoeuver the missile in flight, allowing it to counter inaccuracies in the missile or to follow a moving target. There are two main systems: vectored thrust (for missiles that are powered throughout the guidance phase of their flight) and aerodynamic maneuvering (wings, fins, canards, etc).