Soyuz flies a two-month endurance mission

From Nov. 30, 1973, until Jan. 28, 1974, a Soyuz spacecraft without crew secretly orbited the Earth, testing the limits of its onboard systems and setting a new record for its autonomous mission.


Kosmos-613 mission at a glance:

Soyuz 7K-T No. 34A, Kosmos-613
Launch date
1973 Nov. 30
Launch site
Landing date
1974 Jan. 28
Autonomous test flight
Mission duration
60 days

Changing goals

The long-duration autonomous flight of the Soyuz spacecraft was recommended by the commission that investigated the Soyuz-11 accident in 1971. (774) The obvious goal would be to test the endurance of the onboard systems in a solo flight, something previously not exceeding 18 days. Although in 1971 Soyuz-11 had operated in orbit for more than three weeks in a joint flight with the Salyut space station, the subsequent disaster raised questions about its performance in longer flights. Ultimately, Vehicle 7K-T No. 34 was configured for a two-month mission without a crew.

This particular ship was originally intended for carrying a pair of cosmonauts to the second Soviet space station, DOS-7K No. 2 (DOS-2).

As of early March 1972, its launch to DOS-2 was expected between June 10 and 15, 1972, after the launch of Vehicle No. 33A between May 15 and 20, 1972.

In July 1972, the preparation of Vehicle No. 34 was apparently marked by an accidental activation of some pyrotechnic device, which triggered the July 12, 1972, emergency meeting at the Ministry of General Machine-building, MOM, which oversaw the Soviet rocket industry. Nevertheless, the ship was back in working order by July 26, when it was sent into the vacuum chamber for air leak checks, as part of the ongoing campaign for the DOS-2 station, which ended with a launch failure on July 29, 1972.

DOS-2 is lost

According to notes by Vasily Mishin, within hours after the loss of DOS-2, he already had a plan for an autonomous flight of Vehicle No. 34, because "it had many new systems that needed (flight) tests." (774)

At the time, the mission was expected to carry a crew. All cosmonauts who trained for the DOS-2 expeditions, including Leonov, Kubasov, Lazarev, Makarov, Gubarev and Grechko began preparing for the solo flight, which was initially expected as early as August 1972, or just within a month after the loss of DOS-2. (231)

By August 2, 1972, Mishin drafted a plan for processing Vehicle No. 34 for launch, while Vehicle No. 33, also left without a job after the loss of DOS-2, was to be mothballed for three months. However by that time, the launch of Vehicle No. 34 drifted to the first half of September 1972 and continued slipping.

Finally, on Sept. 13, 1972, at the meeting of the Military Industrial Commission, VPK, a decision was made to postpone the launch of the 11A511 No. 27 rocket with the 7K-T No. 34 spacecraft indefinitely. Instead, the leadership favored a proposal for an astronomy mission, which required a custom-built Soyuz.

All subsequent attempts by Mishin to revive the flight program only resulted in further delays, indicating that the top officials were against the plan, which was ultimately cancelled. (774) All the cosmonauts who had been training for the mission were moved to the DOS-3 project planned for 1973.

Another change of plans

After the loss of the DOS-3 station on May 11, 1973, officials had to decide what to do with the three crew vehicles — Vehicles No. 34, 35 and 36, because the clock was ticking on the life span of their systems. All three ships were initially expected to be used for unpiloted test flights.

Ultimately, Vehicle No. 34, was sent to be reconfigured during Summer and Fall 1973 for an unpiloted endurance test in orbit under name No. 34A. (231) Modifications likely included the installation of solar panels which would make it possible to re-charge onboard batteries during a two-month flight.

Vehicle No. 34A completes an endurance flight

An 11A511 rocket carrying the Soyuz 7K-T vehicle No. 34A lifted off from Tyuratam on Nov. 30, 1973. Less than nine minutes later, the spacecraft successfully entered a 195 by 295-kilometer initial orbit with an inclination 51.6 degrees toward the Equator. (2)

Without any fanfare, the mission was publicly announced as Kosmos-613. As was the case with several other Soyuz test missions, the Soviet authorities did not acknowledge any connection between the flight and the Soviet piloted space program or provide any other useful details on the mission.

However, the known orbital parameters hinted the probable nature of the spacecraft to Western observers. The question remained about the exact type of the vehicle. Because the launch was preceded by the piloted test launch of Soyuz-12, it was logical to speculate that a new Salyut-type space station had gone into orbit to be followed by a crew vehicle. However, days and weeks went by without a new cosmonaut launch. Instead, over a period of six days, Kosmos-613 maneuvered into a 250 by 400-kilometer orbit, where most of its systems were believed to be powered down for nearly two months, to simulate a joint flight with a space station. The experiment, lasting nearly twice as long as the previous space station mission, certified the spacecraft for upcoming expeditions. (50)

The Descent Module of Vehicle No. 34A then landed on Jan. 28, 1974, apparently without problems. (2)

In 1985, a newly published Soviet space flight encyclopedia listed Kosmos-613 among the Soyuz test missions for the first time, finally acknowledging the nature of the flight. (2)


The article and illustration by Anatoly Zak; Last update: January 28, 2024

Page editor: Alain Chabot; Last edit: January 28, 2024

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