L4 -1963

The L-4 Manned Lunar Orbiter Research Spacecraft would have taken two to three cosmonauts into lunar orbit for an extended survey and mapping mission. It was described in a 23 September 1963 letter setting out the space exploration plan for 1965 to 1975. The L-4 complex, with a total mass of 75 metric tons, would be placed into orbit in a single N1 launch

The L-4 would consist of:

• The trans-lunar injection stage, total mass 58 metric tons. If development of a fourth stage for the N1 was not authorized, this could be replaced by three sequentially-fired Soyuz B 9KM rocket blocks developed for the L-1 and L-2 projects.
• The lunar orbit maneuvering stage, which would have a total mass of 11.5 metric tons. This would break the Soyuz manned spacecraft into lunar orbit and returned it on its transearth trajectory. Five metric tons of propellant would be used for lunar orbit insertion.
• The L-4 spacecraft, which would be a modification of the 7K Soyuz. This would have a mass of 5.5 metric tons after being placed on a transearth trajectory with a descent capsule mass of 2.5 metric tons.

Mass: 17,000 kg (37,000 lb).

• 1963 September 23 - Korolev letter sets out a space exploration plan for 1965 to 1975. -
  The plan included a series of lunar exploration vehicles: the L1, L2, L3, L4, and L5.