In February of 1969, the first launch of the Soviet Moon Rocket, the N-1, exploded. By April, the Soviets still did not have a clear program of subsequent piloted Soyuz fights. In May, the Soviets watched the successful US lunar orbital flight and practice landing of Apollo 10. In June, a Lunar Sample return mission failed when the Block D stage refused to ignite. On July 3rd the second N1 launch failed with a spectacular explosion…
Soviet Luna 15 was designed to take a sample of Lunar soil and return it to Earth
Ye-8 lunar sample return spacecraft – detail of re-entry vehicle Credit: Mark Wade
With the success of Kosmos 146 and in spite of the failures of the first three 7K-Ok’s it was now time to plan for a Soyuz manned mission. The planned involved the launch and docking of two piloted Soyuzes. Soyuz 7K-OK production model number 4 was assigned the role of the active vehicle. The active vehicle was supposed to carry one cosmonaut into earth orbit. Twenty-four hours later, vehicle No. 5 (the passive vehicle) carrying three cosmonauts would be inserted in orbit. After rendezvouing, two cosmonauts from vehicle No. 5 would transfer through open space to vehicle No. 4.
Kosmos 146. A 7K-L1 model.
7K-OK and 7K-L1 Rendezvous Concept. Credit Mark Wade
Chief Designer Mishin proposed a two-launch “stopover” scenario for the piloted flight to the moon. This was similar to one of NASA’s earth orbit rendezvous modes to reach the moon. The gist of the plan was, the UR-500K would insert the 7K-L1 into orbit with no crew. Then the R7 derivative Semyorka would launch the 7K-OK carrying two cosmonauts. If everything went well on the two vehicles, they would dock, and the cosmonauts would transfer from the 7K-OK to the 7K-L1 via spacewalk. Then they would set out for the Moon, and, after flying around it, they would return to Earth.
Vladimir Chelomey Responsible for the Proton Rocket