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The Lunar Orbital Spacecraft, LOK, The LOK, which stands for Lunar Orbital Craft in Russian, could be called the Soyuz on steroids. While from the outside it looked like a stretched version of the original (7K-OK) version of the Soyuz, inside the LOK featured a number of upgrades and unique systems, which enabled it to support piloted lunar expeditions.
LOK technical overview:
The LOK was developed as a part of the L3 lunar expeditionary complex carried aloft by the N1 rocket and equipped with a custom-built Emergency Escape System, SAS. The LOK spacecraft was intended to carry a two-man crew to the lunar orbit, where one of the cosmonauts would transfer to the Lunar Lander, LK. The LK would then separate from the LOK and conduct descent and landing on the lunar surface. After a spacewalk, the cosmonaut would lift off from the lunar surface aboard the LK lander and rendezvous with the LOK spacecraft. After docking and transfer from LK to LOK, both cosmonauts would depart to Earth aboard the LOK. Upon approaching the Earth, the Descent Module would re-enter the atmosphere and perform parachute landing. Development history In the heat of the Moon Race of mid-1960s, the Soviet designers at OKB-1, specialized in manned spacecraft, faced overwhelming challenges. While their rivals in the US concentrated on a single Apollo system for the lunar expedition, Korolev and his associates, had to split long days and sleepless nights between Earth-orbiting Soyuz, circumlunar L1, and lunar-landing L3 complex. Basic configuration of the L3 complex, which included LOK spacecraft was formulated by 1963, or roughly two years behind a similar effort in the United States. Design of the LOK spacecraft The overall appearance of the LOK spacecraft did bore a superficial resemblance to the Soyuz spacecraft from which it certainly derived. Like its predecessor, the ship included the bell-shaped Descent Module, carrying the crew, the bulbous Habitation Module, providing a working and living quarters, and the Aggregate Compartment with all the service systems. But that's where the similarities between Soyuz and LOK would mostly end. First of all, all three original compartments of the Soyuz were drastically re-designed to support lunar missions. LOK also had two additional sections or modules — the DOK maneuvering pod in front and the Power Module nestled on back of the Aggregate Compartment. The DOK autonomous propulsion unit carried its own tanks with propellant for four clusters of maneuvering engines. It was topped with a docking mechanism and carried navigational antennas on its exterior. With its aft bulkhead the DOK unit was bolted to the Habitation Module. Structurally, the Habitation Module was borrowed from Soyuz, but it was extended with a slightly conical ring inserted at its equatorial area between the two hemispherical sections forming the module. Additionally, the egress hatch of the module was enlarged to facilitate spacewalks. The top hemisphere of the module received a blister with a forward-facing window, which could help with navigation during rendezvous. The bottom hemisphere had an opening into the Descent Module, which had only one parachute container instead of two on Soyuz. A special ring adapter connected the Descent Module to a pressurized Instrument Compartment below, which itself was a part of the Instrument and Aggregate Module. The ring adapter also carried four clusters of attitude control engines and their fueling interfaces. The rest of the aggregate compartment was primarily occupied by a spherical propellant module. Around it was wrapped a radiator of the thermal control system interrupted by some navigation sensors and star trackers. The Aggregate Compartment was complete with a skirt-shape adapter interfacing with the payload fairing. On its exterior, the skirt carried bulky equipment of fuel cells that supplied the whole vehicle with electricity. Using cryogenic liquid hydrogen and oxygen, the system was blanketed with its own radiator cover.
Power supply: The most notable difference between the original Soyuz crew vehicle and the LOK variant was the power supply system. Unlike solar panels which provided electrical energy for the 7K-OK spacecraft, the LOK was initially expected to carry a pair of Radio-Isotope Thermal and Electric Generators, RITEGs attached to beams extending from the Aggregate Compartment. In the course of development, the RITEG's were replaced with liquid hydrogen/oxygen-powered fuel cells, EKhG, similar to those used on the US Gemini, and Apollo spacecraft. In addition to generating electrical energy, fuel cells would output critically needed breathing oxygen and potable water as byproducts, thus greatly increasing spacecraft's life-support capacity. The fuel cells were mounted on the conical adapter connecting the LOK spacecraft to the fairing which enclosed the LK lunar module. As a result, the adapter was made to be a part of the LOK and re-named the Power Section, EO, (from the Russian Energetichesky Otsek). The development of fuel cells was delegated to the Ministry of Medium Machine-building, known as MSM or Minsredmash, which was responsible for nuclear technology in the USSR. (78) The EKhG system was not ready for first tests of the N1 rockets in 1969, but it was actually installed on the mockup of the N1/L3 complex No. 1M1A, and tests loading of the fuel cells with hydrogen and oxygen was conducted from Nov. 1 to Dec 29, 1971. Another such fueling took place during the stay of the flight vehicle on the launch pad from Aug. 24 to Nov. 23, 1972. Life-support system: The LOK spacecraft would also carry more capable life-support system than the original Soyuz 7K-OK. From around 1964, NIIKhIMMash research institute of the Ministry Chemical Machine-building was working on closed-loop systems of recycling water, which could enable much longer presence of people in space. Specifically for the LOK program, NIIKhIMMash was developing system called Rosa (Russian for "dew"). It would receive humidity collected from the LOK's atmosphere, separate liquids and gases filter out water and mineralize it for drinking. The Rosa unit would be installed in the habitation module along with the standard life-support hardware inherited from the Soyuz. During its unmanned test flights, which could include circumlunar missions, the LOK would also carry a special system imitating the release of humidity with the sweat by the human body. The system aimed to test the performance of the Rosa system. Such system was apparently installed on the LOK spacecraft carried in the last two of four ill-fated launches of the N1 rocket. (200) Docking system: To conduct mechanical docking between the LOK and LK, the L3 complex carried Kontakt system, rather than the Igla installed on the regular Soyuz. The LOK spacecraft carried active part of the Kontakt system, including a main engagement probe and four peripheral amortization devices. It was enough for the main probe to enter into any of multiple holes of the docking plate of the LK to provide a reliable docking. The docking mechanism of the Kontakt system did not provide internal tunnel for the crew transfer between LOK and LK, however it helped to reduce mass deficit during the development of the N1-L3 complex and simplified overall design of the mechanism. (201)
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