Spacecraft propulsion is any
method used to accelerate spacecraft and artificial
satellites.
Orbital
launch systems are rockets and
other systems capable of placing
payloads into or
beyond Earth orbit. All launch vehicle propulsion systems employed to date have been
chemical rockets falling into one of three main categories: •
Solid-propellant rockets or solid-fuel rockets have a motor that uses
solid propellants, typically a mix of powdered
fuel and
oxidizer held together by a
polymer binder and molded into the shape of a hollow cylinder. The cylinder is ignited from the inside and burns radially outward, with the resulting expanding gases and aerosols escaping out via the nozzle. •
Liquid-propellant rockets have a motor that feeds liquid propellant(s) into a combustion chamber. Most liquid engines use a
bipropellant, consisting of two liquid propellants (fuel and oxidizer) which are stored and handled separately before being mixed and burned inside the combustion chamber. •
Hybrid-propellant rockets use a combination of solid and liquid propellant, typically involving a liquid oxidizer being pumped through a hollow cylinder of solid fuel. All current spacecraft use conventional chemical rockets (solid-fuel or liquid bipropellant) for launch, though some have used
air-breathing engines on their
first stage. == Current rockets ==