The Martian Piloted Complex or MPK was a Soviet Union Human mission to Mars proposed by Mikhail Tikhonravov. It featured a six-Cosmonaut crew on a 900-day mission, with a launch in 1975.
The craft would have a mass of 1,630 metric tons and land a crew on Mars for a one-year expedition. It would take 25 N1 rocket launches to assemble the MPK.
References
Martian Piloted Complex Wikipedia(Text) CC BY-SA