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A GEM-40 strap-on booster for a Delta II launch vehicle.

A booster rocket (or engine) is either the first stage of a multistage launch vehicle, or else a shorter-burning rocket used in parallel with longer-burning sustainer rockets to augment the space vehicle's takeoff thrust and payload capability.[1][2] (Boosters used in this way are frequently designated "zero stages".)[citation needed] Boosters are traditionally necessary to launch spacecraft into low Earth orbit (absent a single-stage-to-orbit design), and are especially important for a space vehicle to go beyond Earth orbit.[citation needed] The booster is dropped to fall back to Earth once its fuel is expended, a point known as booster engine cut-off (BECO).[3] The rest of the launch vehicle continues flight with its core or upper-stage engines. The booster may be recovered and reused, as was the case of the Space Shuttle.[1]

Drop-away engines

The SM-65 Atlas rocket used three engines, one of which was fixed to the fuel tank, and two of which were mounted on a skirt which dropped away at BECO. This was used as an Intercontinental ballistic missile (ICBM); to launch the manned Project Mercury capsule into orbit; and as the first stage of the Atlas-Agena and Atlas-Centaur launch vehicles.[citation needed]


The Titan III, used by the United States Air Force as an unmanned heavy-lift vehicle, was developed from the Titan II launch vehicle by adding a pair of strap-on solid rocket boosters (SRB). It was also planned to be used for the Manned Orbital Laboratory program, cancelled in 1969.[citation needed] Strap-on boosters are sometimes used to augment the payload or range capability of military jet aircraft.[citation needed]

NASA's Space Shuttle was the first manned vehicle to use solid-fueled boosters as strap-ons. The solid boosters consisted of stacked segments, and were recovered and reused multiple times.[citation needed]


The booster casings for the Space Shuttle Solid Rocket Booster were recovered and refurbished for reuse from 1981–2011 as part of the Space Shuttle program.

In a new development program initiated in 2011, SpaceX developed reusable first stages of their Falcon 9 rocket. After launching the second stage and the payload, the booster returns to launch site or flies to a drone ship and lands vertically. After landing multiple boosters both on land and on drone ships, a landed stage was first flown again in March 2017: Rocket core B1021 was used to launch both a re-supply mission to the ISS in April 2016 and the satellite SES-10 in March 2017.[4] The program is intended to reduce launch prices significantly.

Use in aviation

Rocket boosters used on aircraft are known as jet-assisted take-off (JATO) rockets.

Various missiles also use solid rocket boosters. Examples are:

See also


  1. ^ a b "Rocket Staging". US: NASA. Retrieved October 12, 2018.
  2. ^ "Solid Rocket Boosters". US: NASA. Retrieved October 12, 2018.
  3. ^ Greicius, Tony (March 8, 2011). "Mars Reconnaissance Orbiter – Launch Vehicle Summary". US: NASA. Retrieved April 20, 2019.
  4. ^ Grush, Loren (March 30, 2017). "SpaceX makes aerospace history with successful launch and landing of used rocket". The Verge. US. Retrieved April 15, 2017.