Space launch is the earliest part of a flight that reaches space. Space launch involves liftoff, when a rocket or other space launch vehicle leaves the ground, floating ship or midair aircraft at the start of a flight. Liftoff is of two main types: rocket launch (the current conventional method), and non-rocket space launch (where other forms of propulsion are employed, including airbreathing jet engines or other kinds).
Rocket launch is the only current way to reach space. In some cases an airbreathing (jet engine) first stage has been used as well.Non-rocket space launch is a launch into space where some or all of the needed speed and altitude are provided by something other than expendable rockets. A number of alternatives to expendable rockets have been proposed. In some systems such as Skyhooks, rocket sled launch, and air launch, a rocket is used to reach orbit, but it is only part of the system.
