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The USSR's first known rival to Apollo

Comparable to the American Nova project, which preceded the Apollo in the early years of the Moon Race, the 19K spacecraft would be a leviathan of the Soviet space fleet designed to carry cosmonauts directly to the lunar surface without first entering lunar orbit or leaving the "mother ship" in orbit around the Moon. The four-part complex likely represented the first detailed Soviet architecture intended to beat the Apollo astronauts to the Moon, yet the 19K project remained practically unknown half a century after the first lunar landing.

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A hypothetical poster dedicated to the 19K lunar lander.


Drafting the system

In May 1962, the OKB-1 design bureau, led by Sergei Korolev, completed the preliminary design of the N1 super-heavy rocket, which at the time, was expected to have a payload of 75 tons to the low Earth's orbit, enough to launch a variety of ambitious projects. However, despite the highly publicized decision by the United States to send human expedition to the Moon, the Soviet government was not in a hurry with a parallel response, preferring instead a rather slow-paced evaluation of its strategic goals.

On September 24, 1962, the Central Committee of the Communist Party and the Soviet of Ministers approved decree No. 1022-439, which delegated the Academy of Sciences and the Ministry of Defense the task of selecting the most important scientific and military spacecraft that could be launched on the N1 rocket. Once these projects were prioritized, the rocket industry was expected to spend another month coordinating the development plan for the chosen projects with the State Committee for Defense Technology, GKOT; Radio-electronics ministry, GKRE; and the State Committee for Automation and Machine-building.

Inside the OKB-1 design bureau, Departments No. 3, 9, 17 and 29 were mobilized to conduct their own studies of possible tasks for the N1. They had early results by the beginning of February 1963, when the Academy of Sciences and the Ministry of Defense put forward their ideas on the N1 payloads.

According to a report that was reviewed by the Scientific Council at OKB-1 on April 22, 1963, a total of four architectures were chosen as preferred out of 26 possible schemes to put cosmonauts on the lunar surface. At the time, the lunar exploration studies were still conducted in parallel with the research on possible uses of the N1 for Earth-orbiting vehicles, the exploration of Mars and Venus and robotic missions to other planets of the Solar System. The work also coincided with the ongoing effort to develop the Soyuz complex which could send a five-ton vehicle with a crew on a circumlunar mission or soft-land a 600-kilogram probe on the surface of the Moon. Still, the focus of the May 1963 document was clearly on the lunar expedition.

The 19K-21K design and flight scenario


Because only a few rudimentary images of the 19K vehicle were available at the start of the work on this section in 2015, some assumptions had to be made during the digital recreation of the vehicle. For example, the design of the interface between the 19K space tug and its strap-on orbital maneuvering section had to be completely interpreted. The same applies to the docking mechanism between the 19K expeditionary vehicle and its 21K refueling tankers. (This page displays only a small fraction of currently available renderings.)

The favored scenario for sending cosmonauts to the Moon, as envisioned in early 1963, required three N1 rockets launching a pair of 21K tankers and a partially fueled 19K lunar expeditionary system. All three vehicles were expected to have a liftoff mass of between 73 and 75 tons and be able to link up with each other in the Earth orbit with an altitude of 300 kilometers. The advance launches of the tankers were also seen as validation flights for the N1 rocket, before committing to the launch of the most complex and expensive expeditionary vehicle.

At the time of its launch on the N1 rocket, the 19K expeditionary vehicle would include the following components:

  • The unfueled trans-lunar acceleration stage;
  • The fueled (lunar) braking stage;
  • The variable-thrust propulsion system with the lunar landing and ascent structure;
  • The fueled lunar ascent stage;
  • The maneuvering tug, responsible for attitude control of the 19K vehicle in the Earth's orbit. The tug would also serve as an interface for the dockings of the tankers during the refueling in the Earth's orbit.

After entering the Earth's orbit at an altitude of around 300 kilometers, the 21K tankers would dock one by one to the 19K vehicle and pump between 125 and 128 tons of propellant into the trans-lunar acceleration stage of the 19K vehicle.

Only after the successful fueling of the 19K vehicle would the cosmonauts be separately delivered to the Earth-orbiting vehicle. They would arrive aboard the 5-ton L3 spacecraft derived from the 7K crew ship originally developed within the Soyuz project. It would be launched by a medium-sized booster based on the flight-proven R-7 missile.

After the successful docking of the crew vehicle, the 19K complex would shed its maneuvering tug, attached to the aft section of the trans-lunar injection stage, exposing its propulsion system.

The completed expeditionary complex (with the 7K crew ship still attached) would then fire its four main engines, accelerating toward the Moon.

The empty trans-lunar ejection stage would then separate and all the subsequent orbit corrections during the cruise from the Earth to the Moon would be performed with the main engines of the lunar braking stage.

Upon approaching the Moon, the spacecraft would use a direct descent to the lunar surface without entering lunar orbit. The main propulsion system of the lunar braking stage would perform most of the deceleration during the descent to the Moon, before separating from the landing vehicle. The ship would complete the touchdown using the variable thrust engines on the landing and ascent structure.


The 19K vehicles on the surface of the Moon.

After the completion of the sorties on the lunar surface, the main engine of the ascent stage would be used to lift off from the lunar surface, leaving behind the landing gear structure.

The ascent vehicle would enter a direct Earth-return trajectory, again skipping the lunar orbit. After accelerating the spacecraft to escape the lunar gravitational field, the ascent stage would separate from the L3 spacecraft. The crew would use the KDU propulsion system aboard the L3 vehicle for the trajectory corrections necessary to reach the Earth and perform the atmospheric entry.

On approaching to the home planet, the crew capsule would separate and parachute back to Earth.

Pros and cons

The main advantage of the preferred plan in the 19K-21K architecture was the opportunity to perform all the rendezvous and docking operations in the Earth's orbit instead of the lunar vicinity, where such maneuvers were considered much more technically difficult due to much farther distance from Earth. In addition, unlike any lunar rendezvous schemes, the proposed scenario did not require the crew to leave the return vehicle and thus depend on risky docking in the Earth's orbit for the return home.

The main drawback of the plan was some time limitations on the launch windows when the expedition could depart toward the Moon.

This architecture would also require three successful launches of the yet-to-be-built N1 super rocket and three rendezvous and docking operations, which had never been tried at the time when the plan was drafted in 1963.

However, the failure of any individual component to reach orbit or rendezvous with its target would not necessarily mean the loss of other vehicles of the expedition.

For example, the 19K expeditionary complex would stay on the ground until both 21K tankers were safely in orbit and ready to re-fuel it in orbit, while the aborted launch or docking of the crew with the 19K vehicle could theoretically be repeated with a backup L3 vehicle.

(To be continued)


L3 19K-21K complex specifications as of 1963:

Mass at launch to the Moon 200 tons
Mass at approach to the Moon 62 tons
Mass on the Moon 21 tons
Mass at return to Earth 5 tons
Mass at descent to Earth 2.5 tons
Number of dockings 3
Number of N1 vehicles for the assembly of the system 3
Type of launch vehicle for the crew delivery 11A511
Crew 2-3


The L3 (Soyuz 7K) vehicle at a glance:

Mass of the fueled spacecraft 5 tons
Mass of the descent module with the crew 2.5 tons
Crew 2 (?)


The 19K vehicle at a glance:

Mass of the fueled 19K rocket without strap-on section 156 tons
Mass of refuelable propellant (?) 129 tons
Mass of fueled strap-on section 8 tons


The 21K vehicle at a glance:

Mass of refuelable propellant 65 tons
Mass of the section for rendezvous and orbit correction 10 tons
Number of tankers for a complete fueling of the system 2

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The article and illustrations by Anatoly Zak; Last update: August 7, 2019

Page editor: Alain Chabot, Last edit: July 17, 2019

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Keldysh and Korolev

Mstislav Keldysh (left) and Sergei Korolev were key figures behind the N1 project. Korolev went to great lengths to ensure the support of skeptical military officials for the N1 rocket, while Keldysh tried to find scientific justification for the project.



This is apparently the only publicly available historical depiction of the 19K and 21K vehicles. It was a part of a report discussed at the Scientific Council of the OKB-1 design bureau on April 22, 1963. Credit: RKK Energia


The preferred scenario of the Soviet lunar expedition as of April 22, 1963. Credit: RKK Energia


The 21K tanker approaches the 19 complex in the Earth's orbit. Click to enlarge. Copyright © 2019 Anatoly Zak


The L3 crew vehicle prepares to dock with the 19K complex in the Earth's orbit. Click to enlarge. Copyright © 2019 Anatoly Zak


The 19K spacecraft jettisons its maneuvering tug in preparation for trans-lunar injection maneuver. Click to enlarge. Copyright © 2019 Anatoly Zak


Digital re-creation of the 19K lunar lander. Copyright © 2019 Anatoly Zak


The 19K expeditionary complex lifts off from the surface of the Moon. Copyright © 2019 Anatoly Zak