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

• Delta II (optional boosters plus optional third stage)
• Saturn V
• Vanguard
• Ariane 4 (optional boosters)
• Ariane 2
• Ariane 1 (four stages)
• GSLV (three stages and boosters)
• PSLV (four stages)
• Proton (optional fourth stage)
• Long March 5 (optional boosters and optional third stage)
• Long March 1, Long March 1D
• Zenit-3SL

Examples of two stages with boosters

Other designs (in fact, most modern medium- to heavy-lift 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.

• US Space Shuttle — SRB first stage ; External Tank + SSME second stage ; OMS on internal tanks third stage ;
• Ariane 5
• Delta III
• Delta IV-Medium+ and -Heavy
• H-IIA, H-IIB
• Soyuz
• Titan IV
• Long March 2E, Long March 2F, Long March 3B

See also

• SSTO - Single-stage-to-orbit
• TSTO - Two-stage-to-orbit