Twenty-five years ago today — March 31, 1987 — the Soviet Union launched the Kvant-1 space station module from the Baikonur Cosmodrome atop a Proton K booster.
(Kvant-1 diagram. NASA image from Wikimedia Commons.)
Kvant-1 was “a specialized module left over from the Salyut-7 program.” Once installed on the Mir space station, the module not only expanded the station’s experimental apparatus but its six “gyrodynes” — i.e., control moment gyroscopes, as opposed to the rotorcraft of the same name — also improved Mir’s attitude control.
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