It was planned to land the L3M on the moon for two week exploration missions after the American Apollo program was wound up. The L3M was cancelled together with the L3 in 1974, effectively ending Soviet plans for exploration of the moon.
Concurrent with DLB studies, OKB-1 was already developing more powerful versions of the N1 to launch heavier payloads to the moon. The N1 growth study S. P. Korolev had signed shortly before his death had foreseen the wide use of oxygen-hydrogen propellants in modified versions of the N1 launch vehicle.
The 1965 study foresaw development of a Block V-II Lox/LH2 replacement for the Block B second stage of the N1. At OKB-276 N. D. Kuznetsov led a project to develop a liquid oxygen/liquid hydrogen version of the NK-15V engine with a flight thrust of 200 metric tons for use in this modernized version of the second stage of the N1. However Kuznetsov was having enough difficulty in completing satisfactory development of the conventional version of this engine for use in the basic N1 and his 200 metric ton engine did not reach the hot firing test stage.
While these more ambitious plans would not be realized, the collectives OKB-2 (A. M. Isayev) and OKB-165 (A. M. Lyulka) were continuing studies and basic development that had begun in 1961. The first Russian use of hydrogen as a fuel was planned for rocket stages of relatively small size (with up to 50 metric tons of fuel). These stages, which were designated Block S and Block R, were to be introduced in place of N1 Blocks G and D as part of a modernized L3M lunar spacecraft complex. Use of oxygen-hydrogen propellants would permit expeditions to the moon of three crew, of which two would walk on the surface of the moon.
Isayev set about adapting the 11D56 engine, with a vacuum thrust of 7.5 metric tons, for the Block R. This engine had originally been designed in the early 1960's for use in the third stage of an uprated Molniya-L launch vehicle. The new Block R for the N1 was to have an empty mass of 4.3 metric tons, a maximum fuel load of 18.7 metric tons, and would have been 8.7 m long and 4.1 m in diameter.
Lyulka developed two variants of a 40 metric ton engine - the 11D54 (with fixed chamber) and 11D57 (with gimbaled chamber). These would be used for the new Block V-III third stage of the N1 (3 to 6 11D54) and in the Block S (one 11D57).
First hot firings of the 11D56 on the test stand began in June 1967. Both the 11D56 and 11D57 engines successfully completed their state development test series.
At the Tsniimash museum in Korolev a photograph was displayed of a dynamic test model of an N1 configuration that had been called N1M. This model shows an N1 first stage, with a Block V-III second stage, and Blocks S and R third and fourth stages. Calculations indicate that a two stage Block A / Block V-III N1 would have a low earth orbit payload comparable to that of the basic N1 (around 95 metric tons). Evidently this configuration was considered as an alternative to a conventional three stage N1 for launching the L3M complex into low earth orbit.
The original draft project for the new N1M-L3M lunar landing complex anticipated use of a two-launch profile. On the first launch a Block R RTB braking stage would be put on a translunar trajectory. The RTB would place itself in lunar orbit. Next, the manned L3M lunar lander would be launched. This new spacecraft was much larger than the LK, with a mass of 21 metric tons landed on the lunar surface. The L3M would dock, tail-first, with the RTB stage in lunar orbit. The RTB would act as a lunar crasher stage. The L3M would separate from the RTB just over the lunar surface, then hover to a soft landing. The crew would spend up 16 days on the surface. Following completion of their work, the landing legs would be left behind, and the L3M would launch itself on a trans-earth trajectory. Just before arrival at earth, the crew would enter their Soyuz capsule, separate from the L3M, and make a lifting re-entry into the earth's atmosphere. It was felt that within the existing funding allocation of the original N1-L3 program, enough N1's would be available to support a series of landings in 1978-1980.
At least two drawings of varying designs for the L3M have emerged to date. In one, the Soyuz return capsule was perched atop the landing stage. A small toroidal crew compartment provided accommodation for space-suited cosmonauts to land the vehicle on the moon. Evidently the crew, which would have been limited to two cosmonauts, would be required to space walk from the Soyuz capsule to the toroidal chamber prior to the landing attempt. A return spacewalk would have to be made after ascent from the surface. This L3M had a landed mass of 21 metric tons on the surface, an ascent mass of 18 metric tons, a trans-earth injection spacecraft mass of 5 metric tons, and sufficient supplies for 14 to 16 days of operations on the surface. This probably represents the original N1M-L3M variant.
In July 1970 Kuznetsov was given authorization to design substantially improved versions of the N1 rocket engines. The N1 that would utilize these engines was designated the N1F and would have a payload to a 225 km orbit of 105,000 kg.
Full go-ahead to develop a liquid hydrogen/liquid oxygen high energy upper stage for the N1F finally came in June 1970. The decision was made to develop a multi-engine Block Sr with a propellant mass of 66.4 metric tons. This single stage would be used in place of the previously-planned Blocks S and R to insert spacecraft of what was now termed the Lunar Expeditionary Complex (LEK) into low lunar orbit. It was also to be used to insert heavy spacecraft into geosynchronous orbit and on interplanetary trajectories.
The revised L3M for use with the Block Sr completed design in 1972. In this version the Soyuz capsule was completely enclosed in a pressurized 'hangar' (the OB, cocooned habitation block) which provided the crew with accommodation space. In this variant the crew could simply step out of the capsule into the hangar area without having to don space suits and conduct an EVA. This L3M would have had a mass of about 23 metric tons landed on the surface and have allowed stays of up to 90 days by a crew of three. The two-launch scenario would still be followed, with a single Block Sr from each N1 launch taking over duties of both the Blocks S and R in the previous plan. The DU engine block would perform the same ascent stage duties as the Block E of the original LK.
With the cancellation of the N1 in 1974, work on the upper stages and spacecraft for lunar expeditions did not end. The designs were simply modified for use on the replacement launch vehicle, the Vulkan.
Crew Size: 3.