The jettisoning of self-contained propulsion units after consumption of their propellants – a crucial technique for improving the mass ratio of space transport systems not using an environmental engine. Among the earliest pioneers of the idea appear to have been Conrad Haas and Johan Schmidlap in the 16th century. However, the first detailed theoretical analysis of staging was done by Konstantin Tsiolkovsky.
Serial staging was used, for example, on the Saturn V moon rockets. The Saturn V was a three stage rocket, which performed two staging maneuvers on its way to earth orbit. The discarded stages of the Saturn V were never retrieved. .
Parallel stagingIn parallel staging, several small first stages are strapped onto to a central sustainer rocket. At launch, all of the engines are ignited. When the propellants in the strap-on's are extinguished, the strap-on rockets are discarded. The sustainer engine continues burning and the payload is carried atop the sustainer rocket into orbit. Parallel staging is used on the Space Shuttle. The discarded solid rocket boosters are retrieved from the ocean, re-filled with propellant, and used again on the Shuttle.
Some launchers, like the Titan III's and Delta II's, use both serial and parallel staging. The Titan III has a liquid-powered, two-stage Titan II for a sustainer and two solid rocket strap-ons at launch. After the solids are discarded, the sustainer engine of the Titan II burns until its fuel is exhausted. Then the second stage of the Titan II is burned, carrying the payload to orbit. The Titan III is another example of a three-stage rocket.
The zero stage is the common name given to a cluster of strap-on boosters that provides thrust additional to that of a sustainer engine, to a spacecraft during ascent into orbit.
Related entry staged-in-orbit
Related category ROCKETRY TERMINOLOGY
Source (text and illustrations): NASA
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