Chelomei's LK spacecraft





Soyuz 7K-OK variant

Compared to its predecessors -- Vostok and Voskhod -- the three-seat Soyuz offered enormous advantages. The most important feature of the new ship would be its rendezvous and docking system.


External design of the 7K-OK (Soyuz) spacecraft.


An upper composite configuration during the Dec. 14, 1966, attempt to launch the Soyuz 7K-OK No. 1 vehicle.



From the publisher: Pace of our development depends primarily on the level of support from our readers!

The Soyuz (7K-OK) spacecraft at a glance:

Crew 1 - 3 people
Mass after separation from the launch vehicle 6.38 tons (2); 6,450 - 6,560 kilograms
Descent Module mass 2,800 kilograms (52) (2,700 kilograms (84))
Spacecraft body length 7.6 meters (52) (7.54 meters (84))
Spacecraft body diameter 2.2 meters
Descent Module length 2.16 meters
Spacecraft maximum diameter 2.72 meters
Solar panels span 8.37 meters
Total habitable volume of two pressurized compartments 10.45 cubic meters (2)
Free habitable volume of two pressurized compartments 6.5 cubic meters (2, 52)
Nominal flight duration 3 - 10 days
Solar panel area 14 square meters
Number of rendezvous and orientation thrusters, DPO 14 (thrust: 10 kilograms)
Number of orientation thrusters, DO 16 (thrust: 1.5 kilograms)
Number of descent control thrusters 6
Number of rendezvous and orbit correction thrusters 2
Initial parking orbit for "active" spacecraft during a joint flight 202 by 222 kilometers
Initial parking orbit for "passive" spacecraft during a joint flight 190-210 by 270-290 kilometers
Orbital period 88.5 - 89 minutes
Orbital inclination 51 degrees 43 minutes
Time required for rendezvous and docking of two spacecraft No more than 65 minutes
First launch (unmanned) 1966 Nov. 28 (Kosmos-133)
Total spacecraft launched 16 (8 unmanned, 8 manned)*

*Does not include Vehicle 7K-OK No. 1 destroyed on the launch pad in December 1966.

Spacecraft design

The capability of spacecraft to link up in orbit promised to overcome the limitations of existing rockets by assembling bigger vehicles out of smaller components. Because the original design of the Soyuz complex envisioned the use of unmanned tankers, the new spacecraft inherited the fully automated Igla (needle) rendezvous system.

The Soyuz spacecraft also sported a newly developed habitation module, which provided most life-support functions for the crew, including a toilet, thus enabling much longer missions than those possible aboard Vostok. In addition, this ball-shaped habitation compartment could also double as an airlock for space walks. To perform the transfer of crew members between docked ships, the Soyuz carried new spacesuits. However, the developers chose not to equip crew members with protective suits inside the spacecraft, because Vostok and Voskhod missions had never experienced loss of pressure.


Internal design of the 7K-OK (Soyuz) spacecraft.

During the transition from Vostok to Soyuz, most of the existing internal systems developed for human space flight were radically reworked. Practically all the hardware was built on the principle that any failed component would have to be backed up by an alternative system, ensuring the safety of the crew.

The flight control system, developed at Department 27 led by Boris Raushenbach, could maintain orientation of the spacecraft in orbital and inertial coordinate systems and it could also place the vehicle in the correct attitude for orbital and deorbiting maneuvering, rendezvous and point its solar arrays toward the Sun.

For the first time in the Soviet space technology, the Descent Control System, SUS, could steer the descent capsule during its return to Earth and maintain the correct attitude to produce aerodynamic lift. As a result, the crew would enjoy a gentler descent, when compared to loads experienced by pilots aboard Vostok. Several groups of small thrusters were using pressure-fed highly concentrated hydrogen peroxide to maneuver the descent module.

Propellant tanks for the descent control thrusters were initially placed inside the crew capsule, but in 1964, Korolev found this arrangement too dangerous and the tanks were moved to a specially designed niche on the exterior of the module.

Instead of the single braking engine on Vostok capable of just one firing, the Soyuz received a brand-new dual-engine propulsion system, designed for multiple firings in space. The KTDU-35 propulsion system was conceived as an integrated unit comprised of propellant tanks, the main rendezvous and correction engine, SKD, and a two-chamber backup correction engine, DKD, which could be used for a braking maneuver in an emergency.

Soyuz also carried two groups of small thrusters with their own autonomous tanks: small engines, DO, which could be used for attitude control in orbit, and a group of larger engines, DPO, which had an additional rendezvous function.

The brand-new power supply system on Soyuz relied on a pair of solar panels feeding multiple rechargeable batteries.

The multi-functional communications system of the Soyuz spacecraft originally conceived for a lunar flyby missions, enabled the transmission of commands, TV signals and telemetry data, as well as voice communications. Radio signals could also be used to measure the orbital parameters of the ship.


Soyuz 7K-OK development responsibilities at OKB-1/TsKBEM:

Key official(s)
Original studies of the manned lunar flyby vehicle
M.K. Tikhonravov
Development of automated rendezvous methods
B.V. Raushenbakh
Analysis of atmospheric descent problems, crew capsule shape and emergency escape system
V.F. Roshin
Spacecraft structure design
G.G. Boldyrev
Structural material selection and analysis
N.G. Sidorov
Overall development
YaP. Kolyako

*Based on a calculation group of Department 8 from Artillery design bureau TsNII-58, which was absorbed by OKB-1 in 1959. **After August 1963.


Key contractors in the Soyuz 7K-OK project:

Key official(s)
Prime developer
Sergei Korolev, Aleksei Topol
Propulsion system, SKDU
A.M. Isaev
Parachute for landing system, SP
F.D. Tkachev, N.A. Lobanov
Pilot console, landing and escape system testing
N.S. Stroev, V.V. Utkin
Emergency Escape System, SAS
Zavod Iskra
I.I. Kartukov
Launch vehicle and payload section
OKB-1 Kuibyshev branch
D.I. Kozlov
Igla rendezvous system, echoless chambers
A.S. Mnatsakanyan
Kontakt rendezvous system (alternative to Igla)
A.F. Bogomolov
Motion and attitude control system simulator
A.M. Shakhov, I.I. Pogozhev
Attitude control and rendezvous thrusters development support
V.S. Shpak, Yu.B. Sviridov
Long-range communications and telemetry system, DRK
M.S. Ryazansky
Krechet TV system
VNII Television
I.A. Rasselevich
Zarya radio-communications system
Yu.S. Bykov
Mir-3 autonomous recording system
I.I. Utkin
Life-support and landing systems, toilet, water storage
Zavod 918
S.M. Alekseev, G.I. Severin
Components of the thermal control and life-support system
NPO Nauka
G.I. Vornin
Food and medical kits
V.I. Yazdovsky
Atmosphere gas analyzer
V.A. Pavlenko


Next chapter: Origin of the Soyuz 7K-OK variant


Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:



Bookmark and Share

The article and illustration by Anatoly Zak; Last update: April 27, 2017

Page editor: Alain Chabot; Last edit: November 27, 2016

All rights reserved





Basic architecture of the 7K-OK spacecraft (in "active" configuration).


Artist depiction of the 7K-OK variant in "passive" configuration.


A demo of the Soyuz spacecraft with a passive docking port. Credit: MAI


Flight control console inside the original version of the Soyuz spacecraft. Click to enlarge Copyright © 2000 Anatoly Zak


Kazbek chair for the Soyuz spacecraft. Copyright © 2011 Anatoly Zak


Front section of the 7K-OK spacecraft with active docking port.



Soyuz 7K-OK spacecraft during pre-launch processing in Tyuratam.


A 7K-OK spacecraft is being fueled for launch.


A payload section with a 7K-OK spacecraft is being integrated with the third stage of the launch vehicle.



An early Soyuz spacecraft during final processing on the launch pad in Tyuratam. Credit: RKK Energia


Footage from the joint mission of Soyuz-4 and Soyuz-5 spacecraft in 1969 likely captured this view of departing Soyuz-4 spacecraft. Credit: Roskosmos