Chelomei's LK spacecraft





Development of the Soyuz 7K-OK spacecraft

On August 28, 1965, the leading designer Aleksei Topol brought Boris Chertok the official schedule for the development of 7K-OK, which had just been approved by Korolev. Chertok could hardly believe his eyes, because by December of the same year, the document required to build and outfit Soyuz prototypes for 13 different tests, including aircraft drop tests, thermal, static and vibration testing, docking and spacewalk rehearsals and cosmonaut training. The schedule also called for the completion of assembly of two flight-worthy ships in December 1965 and a third spacecraft would have to be ready in January 1966. (466)


The descent module of the Soyuz spacecraft is being prepared for vacuum testing.

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

Soyuz faces delays

To free his workforce and resources for the high-priority 7K-OK project, Korolev cancelled all future missions of Voskhod spacecraft planned for 1966. He also transferred a multitude of projects not directly related to human space flight, including communications satellites, planetary probes and military satellites, from his OKB-1 to elsewhere within the industry.

Still, all these measures were not enough to overcome another major problem: OKB-1's wide network of suppliers struggled to provide a multitude of new systems for the Soyuz.

On Sept. 28, 1965, Korolev wrote to the government that on the condition of contractors supplying all the components for the first two Soyuz spacecraft by October 15, their assembly would be completed in November. It would be followed by factory testing from December 1965 to January 1966. If successful, the first dual launch of the Soyuz spacecraft could then take place in March 1966. (84)

However none of these dates could be met. During a ministry meeting at the end of November, Korolev said that OKB-1 lacked key components for the Soyuz. (466) He voiced the problem again at the traditional gathering of the Communist Party members at OKB-1 on Dec. 10, 1965, but there, Korolev also cited delays at OKB-1's own production plant. (84)

1966: Death of Korolev

Like the entire Soviet space effort, the Soyuz project suffered another setback with the sudden death of Sergei Korolev on Jan. 14, 1966. Vasily Mishin took over the leadership but, by most accounts, he lacked the charisma and management skills of his towering predecessor.

After the loss of Korolev, minister Sergei Afanasiev issued a new schedule for the Soyuz development, which Chertok also characterized as unrealistic. The management at OKB-1 instituted round-the-clock operations at the assembly plant and in the first half of February 1966, the local Party Committee at OKB-1 demanded that its managers catch up with the schedule in the production of Soyuz prototypes by February 15. (466)

In February, trying to free his workforce for the L1 and the L3 projects, Mishin talked to Dmitry Kozlov, the head OKB-1's Kuibyshev branch in Southern Russia, about transferring the 7K-OK project there. (774) However the idea never materialized. Instead, Mishin ordered the transfer of engineering groups at Department 93, which were focused on the Soyuz development, from the main campus of OKB-1 to the former location of a defense factory across the Moscow-Yaroslavl railway in Podlipki. There, they were merged with Department 15, forming a division specialized in Soyuz. (52)

Mishin's notes indicate that as late as June 1966, he was still considering various design changes in the 7K-OK spacecraft, in an effort to make the troubled project less complex. He apparently looked at dropping the fully automated rendezvous system and even getting rid of the habitation module. In April, a swap between the Igla and the Kontakt rendezvous system was also on the agenda.

At the same time, Mishin's associates were pushing in the opposite direction -- for example, Boris Raushenbakh asked for a special simulator for the rendezvous system (774) and Chertok warned that the lack of a fully operational development prototype of the Soyuz would come back to hunt them during test flights. (466)

At the end of 1966, during the overall reorganization of OKB-1 into TsKBEM, Departments 93 and 15 were restructured to form the Development and Design Departments, PKO No. 211, led by G.G. Boldyrev and specialized in the overall Soyuz spacecraft, and PKO No. 212, led by A.G. Reshetin, which focused on the Descent Module, SA, for the Soyuz. Konstantin Bushuev and Pavel Tsybin still oversaw the development. (52)

Ground testing and production

To validate all the new systems for Soyuz and prove their safety, OKB-1 embarked on a major pre-flight testing effort. The most critical tests of the new spacecraft were conducted during 1965 and 1966. They included drops of the crew capsule from an aircraft with the subsequent touchdown on land and in the Black Sea at a test range near Feodosiya in Crimea.

Two out of five planned drop tests resulted in failures when hydrogen peroxide drained from the capsule during the descent burned the lines and cupola of the backup parachute. The problem was resolved by burning the propellant simultaneously through all the nozzles of the attitude control system to neutralize its propulsive effect on the movement of the capsule. Two additional drops of the capsule confirmed that the procedure worked.

The brand-new emergency escape system of the Soyuz spacecraft went through extensive ground testing.

The spacecraft structure underwent static, thermal and dynamic testing, module separation tests and the jettisoning of the payload fairing.

The descent module and its life-support system were tested in a vacuum chamber, including trials with test engineers inside.

A special suspension stand built inside the high bay of Hall 39 at OKB-1 was used to verify dynamics of the spacecraft during rendezvous and docking.

The ship's new engines were also test-fired.


Chronology of the Soyuz 7K-OK project:

1964 Aug. 3: A government decree approves the development of the L3 complex for lunar landing.

1965 Feb. 6: Korolev sends a proposal on the Soyuz docking mission to Sergei Zverev, an official responsible for the formation of a civilian ministry to oversee the Soviet rocket industry. (84)

1965 March 30: Korolev and Mishin meet to discuss a KORD system for the N1 rocket, a technical assignment for the propulsion system of the 7K-OK spacecraft, efforts to reduce mass of the 7K-PLK vehicle and the Lunar Orbiral Vehicle, LOK. (774).

1965 May 28: Korolev and Mishin sign a package of documents on the 7K-OK spacecraft including an assignment for the ship's new S5-35 propulsion system to the design bureau of Aleksei Isaev. (774)

1965 Aug. 17: Korolev receives a letter from the Head of Cosmonaut Training Center, Nikolai Kamanin, with a list of candidates for Soyuz missions. (84)

1966 Jan. 7: A special collegium of the Ministry of General Machine-building, MOM, reviews Soviet space plans and demands an acceleration of the work on the 7K-OK project. (774)

1966 Jan. 11: Mishin discusses a new development schedule for the 7K-OK system with Kremlin official Ivan Serbin and Deputy Minister Viktor Litvinov. (774)

1966 Jan. 13: Mishin discusses a new development schedule for the 7K-OK system with Minister Afanasiev. (774)

1966 Jan. 14: Korolev dies.

1966 Jan. 11: Mishin discusses the 7K-OK project with Minister Afanasiev and top party officials. (774)

1966 Feb. 19: Mishin and Dmitry Kozlov discuss the transfer of the 7K-OK project to Kuibyshev. (774)

1966 Feb. 25: Mishin holds a meeting with his associates on the L1, N1/L3 and 7K-OK projects. (774)

1966 March 4: Mishin and Isaev discuss certification tests for the S5-35 engine of the 7K-OK spacecraft. (774)

1966 April 20: Mishin holds a meeting with Minister Afanasiev who accepts proposals on the 7K-OK project. (774)

1966 June 14: Mishin holds a meeting with the Kremlin official Leonid Smirnov to discuss the simplification of the 7K-OK spacecraft, possibly delegating more role to the pilot. The option of dropping the habitation module is also discussed. (774)

1966 June 15: Mishin reports to the Military Industrial Commission, VPK, on the status of the 7K-OK project. (774)

1966 Aug. 30: Integrated testing of the first Soyuz spacecraft is completed. (466)

1966 Aug. 31: Mishin chairs the Chief Designers Council on the 7K-OK system. (774)


Next chapter: Production of the first Soyuz spacecraft



Bookmark and Share

The article and illustration by Anatoly Zak; Last update: January 20, 2023

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

All rights reserved


insider content



The main propulsion system (INSIDER CONTENT) of the Soyuz spacecraft undergoes test firing. Credit: Roskosmos


The descent module of the Soyuz spacecraft is being prepared for vacuum testing.


Testing of the separation between the Descent Module and the Instrument Module of the Soyuz spacecraft. Credit: Roskosmos


A full-scale prototype of the descent module for the 7K-OK spacecraft dropped from the aircraft to test landing system. Credit: Roskosmos


Solar panel deployment tests on the early prototype of the Soyuz spacecraft. Credit: Roskosmos