Soyuz 7K-TM variant for the US-Soviet joint mission

A specialized version of the Soyuz spacecraft originally known as 7K-TM was custom-designed for the joint mission with the US Apollo spacecraft in 1975. It was equipped with a new type of a docking port dubbed APAS for Androgynous Peripheral Attach System.


A full-scale demo model of the Soyuz 7K-TM spacecraft first displayed at the Paris Air and Space Show in Le Bourget in 1973.

Known specifications of the Soyuz 7K-TM variant (50):

Designation 7K-TM 11F615A12
Spacecraft liftoff mass 6,790 kilograms
Body length 7.13 meters
Crew 2 people
Autonomous flight duration 7.5 days
Launch vehicle 11A511U (Soyuz-U)
First launch (INSIDER CONTENT) 1974 April 3

Origin of the Soyuz 7K-TM variant

A significant easing of tensions between the Soviet Union and the West in the late 1960s led to expanding political, cultural and scientific contacts across the Iron Curtain, marking a short historical period known as detente or "razryadka" in Russian.

And as the Sputnik was the symbol of the Cold War competition at the end of the 1950s, the Apollo-Soyuz project became perhaps the most memorable event of the fleeting detente. The initial idea for the joint flight was first seriously discussed around 1970, and a formal agreement on the Apollo-Soyuz Test Project, ASTP, was reached in 1972.

In parallel with the international talks, managers and engineers at TsKBEM, which led the Soviet space flight program, began internal discussions with its overseeing Ministry of General Machine Building, MOM, about accelerating the ongoing work on a radically modernized Soyuz variant, designated 7K-S, so it could be ready for the joint mission. The obvious rational was that the international status of the project would ensure its funding and faster development.

In 1971, TsKBEM issued technical documentation for the 7K-S variant and, as of August 1972, the bureau's experimental plant in Podlipki near Moscow was assembling two experimental vehicles, with the first scheduled to be completed by December of that year. (1037)

A particular sub-variant of the Soyuz vehicle, to be configured for docking with the Apollo, was identified in the official ministerial communications as Soyuz-M and the same designation was disclosed to the American partners who had only a fragmentary information about the Soyuz upgrade process beyond the scope of a joint flight. (52)

The Soviet of Ministers of the USSR gave a formal go ahead to the development of the Soyuz-M variant with Decision No. 655-rs issued on March 31, 1972, and the scope of the project was further outlined in a MOM Order No. 104 from April 14, 1972.

On Aug. 18, 1972, Head of MOM Sergei Afanasiev followed with Order No. 259, formally assigning TsKBEM the development of a Soyuz-M vehicle based on the already flying 7K-T variant and the planned 7K-S upgrade. The document envisioned the construction of six 7K-T vehicles and six 7K-S ships in 1972 and 1973, for unpiloted and piloted tests, followed by four Soyuz-M vehicles in 1973 and 1974. (1037)

However upon a closer look, it became clear that the upgrades proposed in the 7K-S project were too bold to be implemented in time for the joint mission with the US in 1975. Instead, Head of TsKBEM Vasily Mishin and his deputies Konstantin Bushuev and Boris Chertok came to a meeting of the MOM leadership with a less risky upgrade of the Soyuz dubbed 7K-TM. It would be based as closely as possible on the existing 7K-T variant (11F615-A8).

In the design documentation, the 7K-TM upgrade was designated 11F615A12, while its manufacturing was set to start from Vehicle No. 70, so the entire 7K-TM batch also became informally known as Series 70. At the same time, internal ministerial communications continued referring to a vehicle for a joint flight as Soyuz-M. (52)

7K-TM upgrades


Soyuz 7K-TM components:

1 Androgynous peripheral docking port 12 Antenna of radio-telemetry system
2 UHF antenna (121.75 megahertz) 13 Ground communications antenna
3 Radio/TV antenna 14 Orbit correction and rendezvous engine
4 Orbital (habitation) module 15 Ion orientation sensor
5 Descent Module 16 Solar panel
6 Attitude control light 17 Command and trajectory measurement antenna
7 Attitide control and approach thruster 18 Orientation periscope
8 Blinking light beacon 19 Window
9 Solar orientation sensor 20 Entrance hatch
10 Instrument Module 21 Apollo UHF antenna (259.7 and 296.8 megahertz)
11 Attitude control thrusters    

The most significant change in the design of the 7K-TM (Soyuz-M) variant was the installation of the so-called androgynous docking mechanism, which relied on identical hardware for both vehicles participating in the docking, instead of the "active" and "passive" systems used before. It made it possible for either side to play the role of an active rescue vehicle for a disabled counterpart. The Soyuz also needed considerable changes in the life-support system, to facilitate the transfer from Apollo's pure oxygen atmosphere, as well as a new UHF radio compatible with the Apollo communications system.

Various light beacons and visual targets required for a partner crew to find the passive vehicle in orbit had to be re-instated on the latest version of Soyuz, which in its role of a station transport acted only as an active vehicle.

Additionally, the interior of Soyuz had to be wired for TV transmissions to be used by NASA astronauts during the joint flight and with equipment for ship-to-ship voice communications between the two crews.

Due to the low-pressure oxygen atmosphere on the Apollo, as early as June 1972, Mishin ordered his engineers to evaluate an option for lowering the pressure inside the Descent Module of the 7K-S spacecraft from the normal 750 millimeters of mercury to 450-500 millimeters. (774) That feature was eventually accepted for the 7K-TM variant, but only during the short period of flight necessary to perform docking operations.

Because the joint mission also called for a longer autonomous flight than typical taxi deliveries to the space station, solar panels were re-introduced aboard the 7K-TM variant, extending its potential for a solo mission from 3 to 7.5 days. Finally, various re-arrangements and improvements were made in the interior as well.

Obviously, the 7K-TM variant had to incorporate various upgrades that had been introduced into the baseline 7K-T variant with Vehicle No. 36 (Kosmos-573), which flew in June 1973. (1038)

All the changes, in particular the heavier docking port, led to an overall mass increase of the spacecraft. As a result, in November 1972, the 7K-TM variant moved to the 11A511U version of the Soyuz launch vehicle, which was under development for the 7K-S variant and ultimately boosted the payload of the baseline rocket by around 200 kilograms. The vehicle's Emergency Escape System, SAS, also experienced major changes. Finally, two launch facilities in Tyuratam had to be modified to accommodate a new rocket variant.

Preparing first test flight of the 7K-TM variant

The preliminary design for the Soyuz 7K-TM version of Soyuz was officially completed on Dec. 15, 1972, and the design documentation was ready in the middle of 1973. The flight test program, first approved in December 1972, called for three orbital launches using Vehicles No. 71, 72 and 73, including a first flight in a fully automated mode and the two others with the crews.

In April 1973, all cosmonaut candidates in the Apollo-Soyuz project but the primary crew were assigned to training for test flights of the 7K-TM variant. (231)

The manufacturing of Series 70 had to be conducted in parallel with two other versions of the Soyuz transport vehicles customized for crews deliveries to the civilian Salyut and military Almaz space stations. In early October 1973, Mishin jotted down the following production sequence for various Soyuz vehicles:

Autonomous (factory) tests 7KS (unpiloted)  
(Integrated) tests at the Checkout Station, KIS No. 71 (unpiloted) Shipment (to launch site), Jan. 10-15 (1974)
  No. 61 (unpiloted) (Almaz test flight)
Jan. 10-20 (1974) No. 38 (piloted)  
  No. 39 (piloted) (For) Salyut-4 space station
  No. 40 (piloted)  
  No. 72 (piloted)  
  No. 73 (piloted)  
  No. 74 (piloted)  
  No. 75 (Reserved for) Soyuz-Apollo
  No. 76 (Reserved for) Soyuz-Apollo
  No. 62 (Reserved for) Almaz
  No. 63 (Reserved for) Almaz

The additional challenge was to coordinate the Soyuz upgrade program with test flights of the 11A511U rocket variant, which had to accumulate enough flights with unmanned payloads before it could be certified to carry a crew.

Finally, the assembly of Soyuz Vehicle No. 71, which had to inaugurate flight testing of the 7K-TM variant, had also take into the account various issues uncovered during the flight of Vehicle No. 37 (Soyuz-12), at the end of September 1973 that apparently experienced problems with its thermal control system, STR, and ion-based attitude control equipment. (1041)


The article and illustration by Anatoly Zak; Last update: April 3, 2024

Page editor: Alain Chabot; Last edit: April 3, 2024

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Launch vehicle and spacecraft processing building at Site 2 in Baikonur circa 1970s.


Konstantin Bushuev. Credit: Roskosmos