Energia-launched LOK Credit - © Mark Wade

Lunar orbiter for Energia-launched lunar expedition. The LOK and LK lander would be inserted into lunar orbit by separate Energia launches.

After rendezvous and docking in lunar orbit, three of the five crew aboard the LOK would transfer to the LK and descend to the lunar surface. After 5 to 10 days on the surface, the ascent stage of the LK would return to lunar orbit, and the crew would transfer back to the LOK. The LOK would remain in lunar orbit for a full lunar day (29 days) until returning to earth.

Crew Size: 5. Design Life: 30 days. Orbital Storage: 30 days. Length: 9.60 m (31.40 ft). Maximum Diameter: 5.40 m (17.70 ft). Mass: 30,000 kg (66,000 lb).

• LOK Energia SA.  Other Designations: Spuskaemiy apparat. Part of: LOK Energia. Class: Manned. Type: Spacecraft Module. Purpose: Reentry capsule for crew and lunar samples.

  Descent module of Soyuz configuration but 50% larger dimensionally and nearly twice as heavy.

  Crew Size: 3. Length: 3.20 m (10.40 ft). Basic Diameter: 3.20 m (10.40 ft). Maximum Diameter: 3.20 m (10.40 ft). Habitable Volume: 10.00 m3. Mass: 4,900 kg (10,800 lb).

• LOK Energia PAO.  Other Designations: Priborno-agregatniy otsek. Part of: LOK Energia. Class: Manned. Type: Spacecraft Module. Purpose: Equipment-engine section - Lunar orbit maneuver, trans-orbit propulsion, pressurized crew quarters.

  The LOK provided a pressurized volume for three crew. Within the cabin was a descent module of the same configuration as Soyuz, but almost 50% larger. This would separate just prior to reentry in the earth's atmosphere. Forward was a universal docking system.

  Length: 3.50 m (11.40 ft). Basic Diameter: 4.10 m (13.40 ft). Maximum Diameter: 4.70 m (15.40 ft). Mass: 23,200 kg (51,100 lb). Main Engine Propellants: N2O4/UDMH. Main Engine Propellants: 17,100 kg (37,600 lb).