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I recently came across the, in my opinion, lost potential of the Soviet N1F-L3M program.
http://www.astronautix.com/l/l3m-1972.html

Russian manned lunar lander. Study 1972. Revised L3M design of the L3M lunar lander for use with the Block Sr crasher stage. The Soyuz return capsule was completely enclosed in a pressurized 'hangar'.

Status: Study 1972. Gross mass: 25,000 kg (55,000 lb). Height: 9.30 m (30.50 ft). Span: 9.40 m (30.80 ft).

This L3M would have allowed stays of up to 90 days by a crew of three.

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.

http://www.astronautix.com/n/n1f-l3m.html

In July 1970 Kuznetsov was given authorization to design substantially improved versions of the N1 rocket engines. These would include filters in the propellant lines to prevent ingestion of debris in the turbo-machinery; improved vibration isolation; autonomous operation; and many detailed reliability and durability improvements. So substantial were the changes that they received a completely new series of designations (NK-33, NK-43, NK-39, NK-31 in place of NK-15, NK-15V, NK-19, NK-9V). However it would take over three years of design, development, and test before these new engines would be available.

The N1 that would utilize these engines was designated the N1F (this had no relation to the much more powerful N1F design of 1965 - it was more like the N1U 'perfected' N1 design of the same year). With a payload to a 225 km orbit of 105,000 kg, the N1F would use the new engines, higher density superchilled propellants in all stages, lighter stage structures and numerous detailed changes. Following extensive wind tunnel studies, the boat tail was again redesigned in detail to cope with gas dynamics problems. A cylindrical base reduced the vehicle maximum diameter from 16.9 m to 15.8 m. Four high-thrust roll 'steering' engines were later added to prevent the loss of control that would destroy the 6L launch vehicle. The KORD was completely redesigned, a fire extinguishing system was installed, improved isolation of cabling and electronics was introduced. The telemetry system was reduced in weight while increasing the number of points measured from 700 to 13,000.

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 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 increased payload of the N1F, combined with the Block Sr stage, would allow a single N1F launch to place 27 metric ton spacecraft on the lunar surface. The L3M lander could be increased in capability to allow three month stays on surface.

[...]

Following the fourth N1 failure, Glushko and Kosberg were brought in to provide independent opinions on how the problems could be solved. Neither came up with inexpensive solutions. Kosberg wanted to equip the rocket with new-development 250,000 kgf engines using N2O4/UDMH. Glushko suggested using the RD-253 engines that he had developed for the UR-500 Proton launch vehicle. Interestingly, this very successful design was the final form of the RD-250 engine that Korolev had rejected for the N1 ten years earlier. But even Glushko had to admit that using the RD-253 would mean converting the N1 to N2O4/UDMH propellants, thereby lowering payload performance to unacceptable levels (just as Korolev had argued). Glushko was also rather dubious of successfully synchronizing the operation of 30 engines.

The cash-starved project continued to limp along. Funding to proceed with design and construction of the L3M was not forthcoming. But Kuznetsov's new series of engines had been subjected to huge amounts of ground testing. First/second stage engine testing was completed in September 1972 and third stage testing in November 1973. The next vehicles, 8L and 9L, would be the first to use these new modernized series engines and fully reflect the N1F configuration. The plan was that both 8L and 9L would be launched in the fourth quarter of 1974 in a demonstration of the N1F-L3M dual launch scenario. Confidence was high, based on the massive telemetry received on the 7L flight, that all problems had now been rectified.

On May 18, 1974 the Minister of Medium Machine Building Afanasyev attended a routine meeting of the management of OKB-1. In a few clipped sentences he informed the group that the Politburo had decided to remove Mishin, replace him with Korolev's old nemesis Glushko and combine the two OKB's into a new entity known as NPO Energia. Afanasyev wished the stunned managers every success, and left the room. The N1 program was cancelled

The value of the L3M, from my casual reading, seems immense. Imagine if the United States, having let Saturn-Apollo wind down, believing the Space Race won, had been caught flat-footed by the Soviet Union essentially creating temporary moon bases? The L3M could have made Apollo look like a Sunday picnic in comparison, and laid the groundwork for more permanent moon bases, if the N1F had succeeded. Perhaps the fourth test launch had succeeded? I read that even after the fourth failure, there were still some plans that if the N1F had two consecutive successful flights, then crewed missions would have taken place between 1976-1980, with a moon base sometime after 1980.

How plausible was it that the N1F would eventually work? What would it have taken for it to not be cancelled? If it had, how would the US have reacted? And would Soviet and American lunar bases have come out of it? I'm writing a short story and just need some help on the background for this; I'm not a rocket scientist:coldsweat:.
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