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Soyuz-1 begins its fateful flight

The 7K-OK No. 4 spacecraft lifted off from Tyuratam's Site 1 on April 23, 1967, at 03:35 Moscow Time, exactly as scheduled. Upon reaching orbit, it was publicly announced as Soyuz-1. Observers noticed that unlike Vostok and Voskhod, the very first spacecraft in the series had been given a number -- another hint that a second launch was imminent.

Previous chapter: Final decision to launch Soyuz-1


Exactly 540 seconds after the liftoff, the NIP-16 ground control station manned by Chertok and other key officials received news that the spacecraft had separated from the launch vehicle and had reached a nominal orbit. As Chertok later recalled "we all applauded, but immediately realized that formally flight control had now been in our hands." (466)

Mishin recorded following orbital parameters for the flight:

Planned orbit
Actual orbit
Orbital period
88.62 minutes
88.63 minutes
88.54 minutes
88.56 minutes
51.67 degrees
51.67 degrees
51.72 degrees
51.66 degrees
224.1 kilometers
224.8 kilometers
201.1 kilometers
219.8 kilometers
200.9 kilometers
201.5 kilometers
203.1 kilometers
199.2 kilometers


The very first report based on telemetry data received by NIP-4 and NIP-15 ground control stations informed flight managers that all antennas had deployed, however the left solar panel, which would be critical for power supply onboard, had failed to open. Ground controllers were yet to see the reduced flow of electricity and until Soyuz-1 would reenter the communication range over the USSR almost an hour later, they held hope that solar array had indeed opened, but the sensor confirming the operation had failed to work properly. (466)

In the meantime, a team analyzing the telemetry from the spacecraft reported that a backup antenna of the telemetry system (attached to the solar panel) had not deployed, nor had the cover protecting the 45K star and sun sensor, needed to orient the spacecraft in space. Chertok initially suggested that the cover of the sensor had been blocked by the undeployed solar panel, but it is unlikely, because these two pieces of hardware appeared to be quite far away from each other. More likely, the sensor experienced some fogging on its lenses rendering it unusable. In any case, without a star sensor, Soyuz-1 could not maintain attitude control, necessary for all crucial maneuvers, including spin-stabilization of the craft, or engine firings. In turn, without spin-stabilization, the spacecraft could not effectively expose its only solar panel to the Sun and to re-charge its batteries. (466) As a result, the spacecraft was estimated to have enough power for a 17-orbit flight (slightly more than a day). Fortunately, with only one person onboard, the thermal control system could operate during the full length of the mission. (774)

During the second orbit, as Soyuz-1 reappeared in the communication range, Komarov established voice contact with the ground. He confirmed that the left solar panel had not deployed and the pre-programmed spin stabilization of the spacecraft had failed.

In addition to cutting the power supply, the unopened solar panel created an asymmetry in the configuration of the spacecraft, which made the attitude control difficult, thus preventing spin stabilization, which could ensure reliable power supply. (27) The solar panel, or the telemetry antenna attached to it, probably entangled in the thermal insulation blankets on the aft skirt of the instrument compartment where these two components almost come in contact with each other.

According to Golovanov, Komarov even knocked with his feet on the side of the spacecraft where the simple but stubborn deployment mechanism for the solar array was located, however without success. (246)

Chertok and other flight managers in Crimea realized that preparations for landing should start as soon as possible, while Soyuz-1 still had "juice" in its batteries. However they were preempted by the State Commission, which advised Komarov to repeat attempts to establish spin stabilization of the spacecraft manually. (466) However, at least one such attempt was also unsuccessful, and the cosmonaut apparently overspent propellant of the DO orientation thrusters. (774)

Not until 10:00 in the morning of April 23, had the State Commission officially confirmed an inevitable decision to cancel the launch of Soyuz-2 and prepare a plan for landing Soyuz-1 during its 17th orbit, with a backup reentry opportunities during 18th or 19th orbits.

Mishin's deputy Bushuev proposed a plan where a small braking maneuver would be conducted relying on the joint operation of the main SKD engine and several DPO rendezvous and orientation thrusters. In order to compensate for the shifted center of gravity of the spacecraft with the folded left solar panel, he proposed to move Komarov from his commander seat in the center of the descent module to the left seat. In his records, Mishin identified this maneuver as "korrektsiya prokhozdeniya" or a passing correction. Most likely, it aimed to bring the spacecraft into a right orbit for the upcoming landing. Komarov successfully conducted that "passing correction" at 11:14 Moscow Time, during the 5th orbit of the mission. The maneuver reduced the speed of the spacecraft by between 3.1 and 3.8 meters per second, expending between 102 and 111 kilograms of propellant in the DPO system. However, the ion orientation system displayed some problems during the move. (774)

When around 11:00, Soyuz-1 had entered a prolonged period out of range of ground control stations, flight managers attempted to summarize all the available information and devise a plan for landing. In addition to problems with power supply, continuous attempts to establish attitude control led to the excessive use of propellant.

During the 6th orbit, Komarov had a communications session with ground control, however the planned TV transmission from the spacecraft was cancelled, probably to save power.

In order to prepare for the critical braking maneuver during the 17th orbit, Chertok proposed an exercise for Komarov in use of manual orientation during the 13th orbit. The cosmonaut would use its periscope, VSK-3, to monitor the position of the vehicle. Because the difficulty of using VSK on the night side of the orbit, engineers considered a combined use of the periscope with ion sensors, in case the braking firing of SKD or DKD engines falls onto the period of darkness.

The DO thrusters could be used to keep the spacecraft in right position, with a separate group of DPO thrusters providing a backup as necessary. Depending on the results of the exercise, either DOs or DPOs could then be used to maintain a correct attitude during the critical deorbiting maneuver. If the attitude control turned out to be impossible to maintain during the deorbiting, or if the SKD braking engine would fail to fire, Soyuz-1 could still deorbit during the 18th orbit, using its gyroscopes for orientation and DO thrusters for the deorbiting burn. As the last resort, a combination of the ion orientation system and the DO thrusters could be used during the 19th orbit. Apparently, in the wake of problems exhibited by the ion orientation during the DPO maneuver in the 5th orbit, Mishin wanted to avoid firing DPOs when the attitude control relied on the ion system. However, the manual orientation could be reliably conducted with both DO and DPO thrusters.

Following the attitude control exercise during the 13th orbit, Komarov was asked to make another spin-stabilization attempt using either DO or DPO thrusters in order to recharge batteries, according to Chertok's plan.

Mission control calculated a total of eight windows for entering spin-stabilization relative to the sun: (774)

Spin stabilization window
Mission orbit
April 23
13th orbit
21:16 - 21:25
14th orbit
22:46 - 22:57
April 24
15th orbit
00:17 - 00:22
16th orbit
01:42 - 02:03
17th orbit
03:10 - 03:22
18th orbit
04:38 - 05:01
19th orbit
06:12 - 06:26
20th orbit
07:45 - 07:59

It appears from Mishin's notes that during the 14th orbit, Komarov reported that the manual attitude control exercise and the subsequent attempt to spin-stabilize the spacecraft had both been successful. Moreover, during the 15th orbit, Komarov tried the ion orientation and maneuvering with DO thrusters, while monitoring the ship's position via the VSK periscope. (774)

According to ground control stations, which maintained contact with Komarov at the time, despite all his efforts, "sun current" (power supply from solar panels) did not exceed 12 or 14 amperes. In the meantime, in order to fully recharge the batteries, they needed input of 23 or 25 amperes. Ground controllers responsible for power supply systems estimated that after the 17th orbit, Soyuz-1 could be forced to switch to a backup battery and they advised flight managers not to postpone landing beyond the 19th orbit.

During the 14th orbit, the head of ballistic team Yastrebov warned flight managers that they have to end their endless debates within next half an hour and make a decision on the flight plan, if they wanted his team to have enough time to calculate all the necessary parameters and prepare instructions to be transmitted onboard Soyuz-1 for landing.

After chaotic exchanges between Crimea and the State Commission at Site 2 in Tyuratam, officials finally settled for a landing attempt during the 17th orbit. Komarov was supposed to use ion sensors to orient the spacecraft in the right direction for the braking maneuver.

During the 16th orbit, Gagarin, who was already in Crimea, related Komarov final instructions for landing using ion orientation and DO thrusters. Komarov re-confirmed that his tests of the system during the 15th orbit had been successful. In remaining few seconds of the communication session, Mishin and Kamanin wished Komarov a safe return. (466)

Next chapter: Soyuz-1 returns to Earth

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The article and illustrations by Anatoly Zak

Last update: September 7, 2018

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The Soyuz (11A511) rocket lifts off with the Soyuz 7K-OK spacecraft from Tyuratam.


The official announcement about the launch of Soyuz-1.