Kosmos 21, also known as 3MV-1A and 3MV-1 No.1, was a Soviet spacecraft. This mission has been tentatively identified by NASA as a technology test of the Venera series space probes. It may have been an attempted Venus impact, presumably similar to the later Kosmos 27 mission, or it may have been intended from the beginning to remain in geocentric orbit. In any case, the spacecraft never left Earth orbit after insertion by the Molniya launcher. The orbit decayed on 14 November 1963, three days after launch. Kosmos 21 was launched at 06:23:34 GMT on 11 November 1963, atop a Molniya 8K78 s/n G103-18 carrier rocket flying from Site 1/5 at the Baikonur Cosmodrome.

Wikipedia: https://en.wikipedia.org/wiki/Kosmos_21. Original timeline Wikipedia link: https://en.wikipedia.org/wiki/Cosmos_program. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1963. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).