Kosmos-573: Reconfirmation of Soyuz fixes

On June 15, 1973, a heavily modified Soyuz 7K-T spacecraft entered orbit without crew or much publicity on its second mission to ensure that all the lessons from the fatal Soyuz-11 crash in 1971 had been learned. In addition, the test flight sought to solve problems encountered during the ill-fated launch of the Salyut space station a month earlier.

The Kosmos-573 mission at a glance:

Soyuz 7K-T No. 36, Cosmos-573
Lunch time

June 15, 1973

Launch site
Landing date

June 17, 1973


Autonomous test flight


209 by 268 km orbit, inclination 51.55 degrees, orbital period 89.2 minutes

Duration of the mission

2 days


Not piloted

Original flight schedule

Soyuz 7K-T No. 36 was originally intended to be the first direct crew transport with two cosmonauts to the second Soviet space station, DOS-7K No. 3 (DOS-3), between two and 10 days after the launch of the orbital laboratory in 1973.

The construction of vehicle no. 36 took most of 1972. As usual, final assembly was conducted at the TsKBEM plant in Podlipki. His boss, Vasily Mishin, indicated in his notes that the testing of vehicle No. 36 was completed in early January 1973. scheduled to be completed on February 21, 1973. However, the spacecraft was still awaiting delivery of its parachute system which had been modified after the loss of the Soyuz-11 crew in 1971.

Beginning in March 1973, the launch of Soyuz 7K-T No. 36 on station DOS-3 was penciled in sometime after May 2, 1973, but in mid-April 1973, the launch of DOS-3 and Soyuz 7K-T No. 36 drifted May 6 and May 8, 1973, respectively.

All tests of vehicle no. 36 had been completed with flying colors at the launch site by mid-April 1973.

In the midst of the DOS-3 launch campaign on the morning of May 7, 1973, when Mishin visited the processing building at Site 2, Soyuz 7K-T spacecraft No. 36 was being prepared for integration with the payload fairing.

At 08:00 Moscow time on May 11, 1973 (a few hours after the launch of DOS-3), the technical management gathered in Tyuratam and gave the go-ahead for the launch of a 11A511 rocket with Soyuz 7K-T No. 36 crew vehicle at the launch pad. However, shortly after, news came that DOS-3 had experienced problems and suddenly vehicle no. 36 had no destination. (774)

New plan for a solo mission

After the loss of the DOS-3 station in May 1973, officials had to decide what to do with the three crew transport vehicles assigned to the orbital laboratory: vehicles no. 34, 35 and 36, because time was running out on the lifespan of their systems.

The issue was obviously more burning for Vehicle no. 36, which had passed its fatal operations, including refueling with hypergolic propellant. The solution was to launch it quickly uncrewed on another test of all upgrades made in the wake of the Soyuz-11 crash that had first been tested during the Kosmos-496 mission in June 1972.

Furthermore, serious problems with the new ion orientation sensor, discovered aboard DOS-3, needed to be addressed urgently and vehicle no. 36, equipped with a similar device, was a convenient test bed.

Meanwhile, Vehicle no. 34 was sent to be reconfigured for an unmanned two-month in-orbit endurance test, while Vehicle No. anticipation of the joint Apollo-Soyuz docking mission. (231)

Vehicle no. 36 completes a two day flight

A 11A511 rocket carrying Soyuz 7K-T vehicle no. 36 took off from Tyuratam on June 15, 1973. Less than nine minutes later, the spacecraft successfully entered an orbit of 209 by 268 kilometers with an inclination of 51.5 degrees towards the Equator.

Since the Soviet authorities wanted to divert public attention from post-crash test missions, which were ill-suited for propaganda purposes, vehicle No. 36 was announced as Kosmos-573, with no mention of the link between this launch and the Soviet manned space program. However, the spacecraft’s observable orbital parameters indicated its commonality with previous Soyuz flights, and this fact did not go unnoticed by Western followers of the program.

On the second day of the mission, the spacecraft lowered its apogee, mimicking the behavior seen during the flight of Kosmos-496 nearly a year earlier.

However, unlike Kosmos-496, which remained in orbit for almost six days, Kosmos-573 disappeared after just two days in orbit.

As it later transpired on June 17, 1973, vehicle no. 36 performed a planned brake maneuver and its descent module was successfully recovered. (50)

Flight results

Unknown to the general public, vehicle no. 36 performed well during its autonomous flight, even exceeding the expectations of engineers on the ground. According to Mishin, the ion-oriented flight experiments included firings of DO and DPO thrusters, providing data on the influence of engine exhaust on the sensitivity of the ion sensor, which had experienced fatal anomalies aboard DOS-3. (774)

On the morning of July 12, 1973, Dmitry Ustinov, who oversaw the rocket and space industry for the Soviet government, opened a meeting on the state of the Soviet human spaceflight effort. In his remarks prepared for the event, Mishin reported that the results of 7K-T mission No. 36 had once again confirmed that the corrective measures and upgrades of the Soyuz 7K-T vehicle implemented after the Soyuz-11 accident had been effective. Mishin stressed that the flight goals were achieved with better results than expected. (774)

In 1985, a recently published encyclopedia of Soviet spaceflight first listed Kosmos-573 among Soyuz test missions, finally acknowledging the nature of flight. (2)

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