Wikipedia
The Vostok-K ( meaning "East"), GRAU index 8K72K was an expendable carrier rocket used by the Soviet Union for thirteen launches between 1960 and 1964, six of which were manned. It was derived from the earlier Vostok-L; however, it featured uprated engines to improve performance, and enlarge its payload capacity. It was a member of the R-7 family of rockets.
The Vostok-K made its maiden flight on 22 December 1960, three weeks after the retirement of the Vostok-L. The third stage engine failed 425 seconds after launch, and the payload, a Korabl'-Sputnik spacecraft, failed to reach orbit. The spacecraft was recovered after landing, and the two dogs aboard the spacecraft survived the flight.
On 12 April 1961, a Vostok-K rocket was used to launch Vostok 1, the first manned spaceflight, which made Yuri Gagarin the first human to fly in space. All six manned missions of the Vostok programme were launched using Vostok-K rockets. In addition to manned and unmanned launches of Vostok spacecraft, the Vostok-K was also used to launch four Elektron satellites, and the first two Zenit-2 reconnaissance satellites.
The last launch was conducted on 10 July 1964, with a pair of Elektron satellites. It was retired in favour of the more powerful Vostok-2 and Voskhod rockets.