The L-1 (Ë-1) or UR500K-L1 (ÓÐ500K-Ë1) program was intended for manned flyaround of the moon. The program took place in 1965-1970. The main purpose of the program was to ensure the priority of the Soviet Union by the first manned mission to the moon. But the goal was not achieved. The lunar spacecraft was developed on basis of Soyuz 7K-OK and was designated as 7K-L1, the designation 11F91 (11Ô91) was used for it as well. An unmanned version of the space vehicle, which was officially called Zond (with Zond-4 spacecraft), was designed to perform flight tests.
The 7K-L1 vehicle was designed to perform manned flyaround of the moon by two cosmonauts. Development of 7K-Ë1 vehicle began at construction department-1 in the 2nd half of 1965 under the leadership of S.P. Korolev, in 1966 it was carried out under the leadership of V.P. Mishin. The spacecraft had to be launched on the moon flyaround trajectory using Proton four-stage rocket. Initial mass of the spacecraft was strictly limited by 5,2 tons because of constraints imposed on Proton launch vehicle. Therefore, the spacecraft did not have habitation module and consisted of descent module and instrument-assembly compartment. Cosmonauts had to perform spaceflight onboard vehicle without spacesuits, but wearing flight suits.
Launch of 7K-L1 manned spacecraft and flyaround of the moon was initially planned to be performed in June, 1967 at a year of 50-th anniversary of Soviet power. Before that it was planned to perform 2-3 unmanned successful spaceflights. Launch of manned spacecraft was continually postponed (last time is was planned to be performed in April, 1970, by 100-th anniversary of V.I. Lenin) due to large number of failures of the launch vehicle and malfunctions occurred in the systems of the vehicles during test flights in unmanned mode.
Three crews were completely trained to accomplish the mission:
1 - Leonov-Makarov,
2 - Bykovskiy – Rukavishnikov,
3 - Popovich-Sevastyanov.
However, in January, 1970, the program was closed. The main reason was the fact that the priority of the first flight to the moon by the Soviet Union had been lost (in December, 1968, U.S. astronauts on board Apollo 8 performed the first flight to the moon in the world). In total, 11 7K-L1 unmanned vehicles were launched in terms of flight development test program. 4 of them did not reach the Earth orbit due to failure of the launch vehicle, 4 spacecrafts performed flyaround of the moon. One spacecraft was not launched in July, 1968 due to failure of D unit during prelaunch preparation of the booster.