Rocket

A rocket (from Italian: rocchetto, lit. ''bobbin/spool'', and so named for its shape) is an elongated flying vehicle that uses a rocket engine to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Unlike jet engines, rockets are fuelled entirely by propellant which they carry, without the need for oxygen from air; consequently a rocket can fly in the vacuum of space, and indeed rocket engines operate more efficiently outside the atmosphere. Multistage rockets are capable of attaining escape velocity from Earth and therefore can achieve unlimited maximum altitude. Compared with airbreathing engines, rockets are lightweight and powerful and capable of generating large accelerations. To control their flight, rockets may use momentum, airfoils, auxiliary reaction engines, gimballed thrust, momentum wheels, deflection of the exhaust stream, propellant flow, and spin, or may simply fly in a ballistic trajectory under the influence of gravity. Rockets for military and recreational uses date back to at least 13th-century China. Significant scientific, interplanetary and industrial use did not occur until the 20th century, when rocketry was the enabling technology for the Space Age, including setting foot on the Moon. Rockets are now used for fireworks, missiles and other weaponry, ejection seats, launch vehicles for artificial satellites, human spaceflight, and space exploration. Chemical rockets are the most common type of high-power rocket, typically creating a high-speed exhaust by the combustion of fuel with an oxidizer. The stored propellant can be a simple pressurized gas or a single liquid fuel that disassociates in the presence of a catalyst (monopropellant), two liquids that spontaneously react on contact (hypergolic propellants), two liquids that must be ignited to react (like kerosene (RP1) and liquid oxygen, used in most liquid-propellant rockets), a solid combination of fuel with oxidizer (solid fuel), or...