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7K-S No. 1L (Kosmos-670)

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The USSR develops new variant of the Soyuz spacecraft — 7KS

Fast-paced upgrades of the Soyuz spacecraft in the early 1970s included work on the most-advanced version of ship at the time, called 7K-S, initially conceived for the military. It never reached operational status but paved the way for the 7K-ST variant (Soyuz-T) which became the workhorse of the Russian piloted space program in the 1980s.

Known specifications of the Soyuz 7K-ST variant:

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The Soyuz-S variant has its roots in the project of a small military space station known as OIS (from the Russian Orbitalnaya Issledovatelskaya Stantsiya). Its design was initiated at the TsKBEM design bureau in the second half of the 1960s, probably as a response to the American Manned Orbital Laboratory, MOL, project and to the Almaz station developed at the rival Soviet TsKBM bureau. Around 1967, while TsKBEM was overloaded with work on the lunar program, the initial design of the OIS station was concentrated at the organization's main branch in Kuibyshev (now Samara) under the leadership of its Chief Designer Dmitry Kozlov. In the framework of the OIS project, Kozlov's team drafted a Soyuz-7K-based military crew transport, which got the design code 7K-S and the production designation 11F732. (In the designation, "S" probably stood for "stantsiya" (station)). Unlike its 7K-OK prototype, the 7K-S variant was expected to have a new docking port providing internal transfer of the crew. (52) The ship was also expected to receive a flight control computer, BTsVM, replacing analog systems, and a modified power-supply system, SEP. (774) Available drawings and photos of the spacecraft also showed a more simplified design of the deployment mechanism on the main rendezvous antenna and a streamlined solar panel design.

Many other upgrades for 7K-S were proposed in the course of the 7K-OK flight test program, even though the new variant retained the overall architecture of its predecessor. The draft design of 7K-S and its initial blueprints were signed on Oct. 14, 1968, while the production documentation and the testing program were both ready in 1969. It coincided with the start of the Salyut space station development at TsKBEM, leading to a decision in February 1970 to cancel the orbital component of the OIS project, but to continue work on the 7K-S crew vehicle, as a follow-on to the original 7K-OK. (52) As of July 1970, up to three cosmonauts were expected to fly aboard 7K-S. (774) It was developed as a multi-purpose vehicle for autonomous missions, probably for the military, but it was also designed to be easily re-configurable into a station transport sub-variant under the designation 7K-ST, (which would later be publicly known as Soyuz-T). (52)

In 1970, with the expectation of a large number of missions, consderation was given to setting up serial production of the 7K-S variant in the Siberian city of Omsk, the home of the PO Polyot rocket factory or at the Progress plant in Kuibyshev, the manufacturer of Soyuz and N1 rockets, as well as military reconnaissance satellites. (774)

All the upgrades to the 7K-OK variant made in the wake of the Soyuz-11 tragedy in 1971 were also incorporated into the 7K-S variant through amendments to the preliminary design approved on Aug. 1, 1972. As a result, the crew size of the new variant was expected to be reduced from three to two people, in order to accommodate safety pressure suits and related life-support equipment.

The military use of the 7K-S variant seemed to be pursued as late as the end of 1972, when head of TsKBEM Vasily Mishin discussed with his deputy Eyvgeny Shabarov, (who oversaw the project at the time), a possible exploratory trip to a weapons manufacturer in Tula (South of Moscow) to discuss development of guided shells for the ship. (774)

In 1974, after a reorganization at TsKBEM, the project was refocused exclusively toward the 7K-ST sub-variant to serve as a future crew delivery vehicle for Soviet space stations. In the meantime, the majority of previously planned autonomous missions aboard 7K-S were incorporated into the space station program. Nevertheless, it was decided to begin flight testing of the all-but-ready 7K-S baseline vehicle to gain more experience. (52)

In parallel, specialists responsible for delivery systems made progress with upgrading the existing Soyuz rocket launcher into the 11A511U variant capable of carrying a heavier payload than the 11A511 version, which opened the door to the re-introduction of a three-person crew aboard Soyuz, but this time, wearing pressure safety suits. As a result, by mid-1974, the decision was made to re-work the 7K-ST station transport variant for three cosmonauts. In the interim, the existing 7K-T two-seater would be used in support of the ongoing Salyut space station program. The return to a three-member crew increased mechanical loads on the ship's parachute system from 2,800 to 3,100 kilograms, (1052) and it also affected the aerodynamics of the Descent Module. (774) Various obsolete systems were also replaced with newer systems. The amount of changes led to a near-complete re-work of the design documentation of the 7K-ST variant and required a great deal of new ground testing. (52, 774)

Because as many as three vehicles were already in production at the time of the latest design changes, the fully configured 7K-ST variant would be available with the fourth flight vehicle (No. 4L). The 7K-ST variant was designed to carry either two or three people and in the former case, a standard cargo container would be installed into the free third seat to maintain the proper balance of the Descent Module.

Next chapter: 7K-S No. 1L mission (Kosmos-670) (INSIDER CONTENT)

The article by Anatoly Zak; Last update: August 6, 2024

Page editor: Alain Chabot; Last edit: August 6, 2024

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A Soyuz 7K-ST during approach to a space station.