Rocket

A rocket is any device that propels itself using reaction mass, please see Newton's 2nd Law of Motion.

Rockets are commonly used when it is necessary to carry all the fuel a vehicle needs (such as in outer space) and there is no other substance (land, water, or air) that a vehicle may push itself with.

A chemical rocket engine may use solid fuel, like the Space Shuttle's SRBs, or liquid fuel, like the Space Shuttle's main engines. A chemical reaction is initiated with the fuel in the combustion chamber, and the hot gasses are forced out the rear of the rocket. This causes the rocket itself to be thrust forward.

Nuclear-powered rockets have also been developed, but never put into use.

Rockets were first developed by the Chinese a long time ago (how long?), using gunpowder.

Rockets range in size from tiny models purchased at a hobby store, to the enourmous Saturn V used for the Apollo program.

In military terminology, a rocket is generally solid-fueled and unguided. Whereas a missle can be either solid or liquid-fueled, and has a guidance system.

/Talk