Rocket, general term for a jet propulsion device propelled by the expulsion of gases generated in a combustion chamber
A rocket in its simplest form is a chamber enclosing a gas under pressure. A small opening at one end of the chamber allows the gas to escape, and in doing so provides a thrust that propels the rocket in the opposite direction.
The combustible propellants of a rocket contain both fuel and an oxidizer, a rocket develops thrust independent of its surroundings, unlike other types of jet engines that utilize oxygen from the atmosphere to burn fuel carried aboard. A rocket engine, therefore, is self-contained and is the only type of device suitable for flight propulsion in outer space.