inertial upper stage

American  

noun

1. a U.S. two-stage, solid-propellant rocket used to boost a relatively heavy spacecraft from a low earth orbit into a planetary trajectory or an elliptical transfer orbit. IUS

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Example Sentences

BY JOVE: The Jupiter-bound Galileo spacecraft attached to the Inertial Upper Stage booster is ejected from space shuttle Atlantis’s payload bay.

From Scientific American