A booster in space-related applications is usually a solid rocket booster: a solid fuel rocket of which two or more are attached to the main rocket to provide the main thrust in the initial phase of the rocket's flight. They form the first stage, though the second stage also starts operating at the beginning. After the first stage is discarded, the second continues. There are also liquid fuel boosters (see also Ariane 4), these are called liquid boosters. Categories: Rockets and missiles | Physics stubs ... Solid fuel is a term given to various types of solid material that provide energy. ... A Redstone rocket, part of the Mercury program A rocket is a vehicle, missile or aircraft which obtains thrust by the reaction to the ejection of fast moving exhaust gas from within a rocket engine. ... For the land-speed record breaking car, see ThrustSSC and Thrust2 For the computer game, see Thrust (computer game) Thrust is a reaction force described quantitatively by Newtons Second Law when a system expels or accelerates mass in one direction to propel a vehicle in the opposite direction. ... The second stage of a Minuteman III rocket Description A multistage (or multi-stage) rocket is, like any rocket, propelled by the recoil pressure of the burning gases it emits as it burns fuel. ... Liquid fuels are those combustible or energy-generating molecules which can be harnessed to create mechanical energy, which in turn usually produces kinetic energy, and which also must take the shape of their container. ... Ariane 4 was an expendable launch system, designed by the European Space Agency and manufactured and marketed by the French company Arianespace. ...

Spacecraft aren't the only vehicles to utilise rocket boosters. Missiles (being atmosphere-bound rockets) often do also. For example, see 2K11 (SA-4) or S-200 (SA-5).