Three-stage-to-orbit


The three-stage-to-orbit launch system is a commonly used rocket system to attain Earth orbit. The spacecraft uses three distinct stages to provide propulsion consecutively in order to achieve orbital velocity.

Examples of three stage to orbit systems

Other designs do not have all three stages inline on the main stack, instead having strap-on boosters for the "stage-0" with two core stages. In these designs, the boosters and first stage fire simultaneously instead of consecutively, providing extra initial thrust to lift the full launcher weight and overcome gravity losses and atmospheric drag. The boosters are jettisoned a few minutes into flight to reduce weight.