A single-stage-to-orbit (or SSTO) vehicle reaches orbit from the surface of a body without jettisoning hardware expending only propellants and fluids. The term usually but not exclusively refers to reusable vehicles. No Earth-launched SSTO launch vehicles have ever been constructed. Current orbital launches are either performed by multi-stage fully or partially expendable rockets or by the Space Shuttle which is multi-stage and partially reusable.
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