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7K-OK


Kosmos-140


N1-3L


 

 

The Soyuz pair makes flawless automated docking

After the problem-ridden first rendezvous in October 1967, Soviet space officials decided to send another unmanned pair of Soyuz spacecraft to dock in orbit. The preparation for the mission was overshadowed by the tragic death in a plane crash of the world's first cosmonaut Yuri Gagarin in March 1968, but, the next month, two Soyuz spacecraft completed the successful automated docking without a hitch.


Kosmos-212

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Joint mission of Kosmos-212 and Kosmos-213 at a glance:

-
Kosmos-212
Kosmos-213
Spacecraft designation
Soyuz, 7K-OK-A No. 8, 11F615, Amur
Soyuz, 7K-OK-P No. 7, 11F615, Baikal
Launch date
1968 April 14
1968 April 15
Launch site
Tyuratam, Site 1
Landing date
1968 April 19
1968 April 20
Mission
Docking with Kosmos-213
Docking with Kosmos-212
Mission duration
~5 days
~5 days
Crew
Unmanned
Unmanned

Preparing the flight

Even before the first historic docking of the two Soyuz 7K-OK spacecraft in October 1967, Dmitry Ustinov, who supervised the rocket industry, instructed the program managers to prepare another unmanned joint mission, no matter what would be the outcome of the first rendezvous attempt. (820) After the death of Komarov in the previous year, the leadership at the TsKBEM design bureau and the Kremlin officials had little appetite to fight this order.

While still on the plane from the mission control in Crimea after the October 1967 flight campaign, top projects managers, including Chertok, Tregub and Agadzhanov had an informal technical meeting, where they concluded that the unreliable ion sensors should be complemented with infrared sensors, which could give the flight control system an additional reference for the local vertical direction in orbit. Also, the problem-prone 45K sensor would have to go through an extensive test program, the engineers agreed. Finally, the mystery that had prevented a complete berthing of the first two vehicles would have to be resolved.

During a meeting on November 11, 1967, considering the status of the 7K-OK project, Chertok apparently made a proposal to reserve already assembled vehicles No. 7 and No. 8 for future manned missions, while the follow-on pair of spacecraft (No. 9 and No. 10) would be configured for an unmanned test flight with necessary design changes. The same upgrades would then be implemented on vehicles No. 7 and 8.

Ultimately, Vehicles No. 7 and No. 8 were ordered to be prepared for another unmanned mission. (466) In parallel, another 7K-L1 vehicle was being readied in Tyuratam for a circumlunar test flight. (774)

Flight program

The second attempt to dock a pair of the Soyuz spacecraft was scheduled to begin on April 14, 1968, with the launch of 7K-OK vehicle No. 8, which would act as the active interceptor during the rendezvous. It was to be inserted into a 202 by 222-kilometer orbit with an inclination 51.43 degrees toward the Equator. During its fifth orbit, on the first day of the flight, the spacecraft was scheduled to perform an orbit correction, which would ensure its close position to Tyuratam at the moment when the Earth's rotation would bring the launch site back into the orbital plane of Vehicle No. 8, around 24 hours after its liftoff. At that point, on April 15, 1968, the "passive" vehicle (No. 7) was scheduled to launch and enter a 190-210-kilometer orbital orbit with the same inclination. Immediately, the active vehicle was to begin rendezvous maneuvers with its newly launched target.

The crucial rendezvous and the joint flight were to take place during the 17th, 18th and 19th orbit in flight for the first spacecraft, with following communications windows between the vehicles and the Soviet ground stations:

Orbit
Beginning of communications
End of communications
Orbit 17
12:17 Moscow Time
12:55 Moscow Time
Orbit 18
14:09 Moscow Time
14:22 Moscow Time
Orbit 19
15:35 Moscow Time
15:49 Moscow Time

Following the docking, the two ships were expected to fly in a single stack for two orbits before undocking and beginning a four-day autonomous missions. With most of its propellant still available, the passive vehicle No. 7 was scheduled to perform orbit-raising and braking maneuvers, while relying on ion attitude-control sensors for orientation, which gave so much grief to engineers in previous missions. Both maneuvers were planned on the second day of the flight for the "passive" vehicle, with acceleration taking place during the 15th orbit, followed by the deceleration on the 16th orbit. Next, during fourth orbit on the third day of the flight, another trajectory correction would be attempted, this time, relying on the joint operation of infra-red and ion attitude control sensors. (774)

Final preparations

With the launch campaign in its final leg, the head of TsKBEM Vasily Mishin arrived at Tyuratam on April 8, 1968. The next day, he visited Site 31, where he found Vehicle No. 8 (slated to launch first) already loaded with propellant and Vehicle No. 7 being prepared for fueling. In his notes, Mishin referred to apparent technical obstacles in the campaign, including a three-day delay related to the parachute system and five days lost on dealing with stray electrical current on the body of the vehicle, apparently due to the low quality of the onboard cables. He also inspected cracks in the fittings of the intertank compartment of Block B, likely referring to the first-stage booster of the Soyuz rocket. A total of 98 issues were discovered during the preparation of Vehicles No. 8 and 7, with 61 issues resolved; in 13 cases, the preparations were allowed to proceed, while 11 problems were linked to conflicts in the technical documentation.

On April 10, Vehicle No. 8 was integrated with the Block I (third stage) and its payload fairing, while Vehicle No. 7 was undergoing final testing after its fueling, followed by its final assembly the next day.

On April 12, at 7:00 in the morning, Vehicle No. 8 was rolled out to the launch pad at Site 31. On the same day, the payload section containing the 7K-OK No. 7 spacecraft was transferred to the assembly building at Site 2, where it was integrated with its 11A511 (Soyuz) rocket.

The next morning (April 13), Vehicle No. 7 was rolled out to the launch pad at Site 1. In the meantime, it was a backup day at Site 31. The integrated "general" tests of Vehicle No. 7 were completed by 17:30 Moscow Time on April 13, leaving April 14, as a reserve.

The State Commission, overseeing the launch operations, met at Site 31 around 11:30 in the morning local time of April 14 and gave the green light to the liftoff of the first spacecraft (No. 8) that afternoon. (774)

As usual, several teams of cosmonauts, who were training for the upcoming manned rendezvous missions, were spread out between the launch site and the NIP-16 ground station in Crimea to monitor the dual test flight. (820)

Vehicle No. 8 lifts off

The Soyuz 7K-OK No. 8 lifted off from Tyuratam on April 14, 1968, at 13:00:0,137 Moscow Time (10:00 GMT). After a smooth ride to orbit, the spacecraft successfully separated from the third stage of the launch vehicle at 13:08:51 Moscow Time.

According to the initial telemetry, the orbit was within specifications and would allow the spacecraft to orbit the Earth safely without any additional maneuvers for more than 50 revolutions.

Orbital parameter
Planned
Actual
Orbital period
88 minutes 58 seconds (+0.37 seconds / -0.92 seconds)
88 minutes 63 seconds
Inclination
51.68 degrees
51.69 degrees
Apogee
225 kilometers (+46/-21)
226.7 kilometers
Perigee
204.3 kilometers (+18/-19)
209.6 kilometers

During the fourth orbit, around 17:33 Moscow Time, as Soyuz reappeared over the Soviet ground stations, mission control radioed the instructions to the ship's flight control system for the upcoming orbit correction during its 5th orbit, at 19:10 Moscow Time.

The maneuver reduced the orbital velocity of the spacecraft by 10.39 meters per second and post-maneuver measurements showed the following parameters:

Parameter
Orbit 1
Planned post-maneuver orbit
Actual post-maneuver orbit
Orbital period
88.74 minutes
88.36 minutes
88.365 minutes
Inclination
51.68 degrees
51.69 degrees
51.68 degrees
Apogee
238.6 kilometers
215.54 kilometers
205.9 kilometers
Perigee
210.2 kilometers
188.86 kilometers
189.4 kilometers

Around that time, the launch was publicly announced as Kosmos-212. (50)

Soyuz makes clean automated docking

The State Commission met again at 10:30 local time in Tyuratam on April 15 to review the readiness of Vehicle No. 7 and its rocket for liftoff. Lt. Colonel V. A. Polyakov reported that the previous day's launch had been flawless, while Patrushev and Yurasov said that the fresh rocket and the spacecraft were in good shape. Ground control stations were also ready.

The passive vehicle 7K-OK No. 7 was launched a day after the first, at 12:34:17.1 Moscow Time (09:34 GMT). According to Kamanin, (who led cosmonaut training) the liftoff was two seconds off the planned time, but at the completion of the orbital insertion, the fresh vehicle ended up just four kilometers from an interceptor vehicle awaiting for it. (820)

The second Soyuz was officially designated as Kosmos-213 and was reported to be in a slightly lower 205 by 291-kilometer orbit than that of Kosmos-212. (50)

Immediately, the automated docking process was initiated. As the pair passed over the IP-15 ground station in Ussuriisk in the Soviet Far East, the ships were just 335 meters apart. At 12:53 Moscow Time, the closure rate between the two vehicles was two meters per second. When they left the communication range at 12:56 Moscow Time, the rendezvous radar on the active ship was reliably locked in on its target. The pressure in the DPO rendezvous thrusters showed healthy 250 atmospheres.

As the subsequent telemetry showed, the mechanical docking between the two spacecraft began at 13:21:30 Moscow Time or just 47 minutes after the launch of the second (passive) vehicle. At the time, they were in a 204.54 by 289.3 kilometer orbit.

The docking was apparently completed at 13:31 Moscow Time (10:31 GMT). (50) Live TV images from orbit confirmed that the spacecraft had formed a solid stack. (820) The two ships remained docked for more than three hours until 14:11 GMT on April 15. (50)

Following the successful rendezvous,a group of cosmonauts led by Georgy Beregovoi, flew from Tyuratam to Crimea to watch the rest of the dual mission. (820)

April 19: Landing of Vehicle No. 8

After spending five days in orbit each, Kosmos-212 (Vehicle No. 8) and Kosmos-213 (Vehicle No. 7) were prepared for landing on April 19 and April 20, 1968, respectively.

On the evening of April 18, Mishin flew to Crimea and at 21:00 Moscow Time, he chaired a technical meeting on the upcoming landing. Again, both ships were reported in good shape.

According to the latest measurements, the spacecraft were in the following orbits:

Orbital parameter
Vehicle No. 7
Vehicle No. 8
Orbital period
88.15 minutes
88.568 minutes
Inclination
51.67 degrees
51.672 degrees
Apogee
198.1 kilometers
187.6 kilometers
Perigee
297.1 kilometers
249.5 kilometers

Mission control planned two opportunities for the landing of the active Vehicle No. 8, during 81st and 82nd orbit on April 19:

Parameter
Orbit 81
Orbit 82
Time of braking engine firing
10:56:32 Moscow Time
12:28:18 Moscow Time
Longitude of the landing site
77 degrees
75 degrees
Time of descent to an altitude of 7 kilometers (parachute release)
11:24:10 Moscow Time
12:55:56 Moscow Time
Latitude at the altitude of 7 kilometers (parachute release)
51.7 degrees
52.7 degrees

On April 19, Vehicle No. 8 fired its DO-2 thrusters reducing its velocity by 85 meters per second. During its maneuver, mission control kept the spacecraft in the proper orientation, relying on ion and infrared sensors. (774)

The descent module of Vehicle No. 8 was reported landing 20 kilometers southwest of the town of Maikolna, not far from from the city of Pavlodar.

The attitude control system worked as planned and the capsule made a controlled reentry using the Landing Control System, SUS. For the first time, the Soyuz demonstrated its capability to provide aerodynamic lift during the flight in the dense atmosphere.

However, due to continuous upgrades to the landing system, both descent modules had their systems for detaching parachutes after touchdown deactivated. (231) As a result, on April 19, unusually strong winds reaching 22 or 23 meters per second at the landing site dragged the capsule around five kilometers. (820)

In the meantime, the full attention of the mission control switched to Vehicle No. 7 still in orbit. The spacecraft was commanded to conduct test orientation for the upcoming braking maneuver, using infrared and ion sensors.

At 18:15 Moscow Time, engineers had a final technical meeting preparing for landing.

April 20: Landing of Vehicle No. 7

At 09:10 Moscow Time, engineers reviewed the latest telemetry data gathered from Vehicle No. 7 during the 93rd, 94th and 95th orbits of the joint mission. The controlled reentry was now scheduled during the 98th orbit of the dual mission, which would be the 82nd orbit for Vehicle No. 7.

During its 97th orbit, the spacecraft passed over the IP-16 station in Crimea, followed by IP-3 in Sary Shagan and IP-15 in Ussuriisk, as ground controllers conducted final preparations for landing. Again, the spacecraft was commanded to turn tail first and maintain its attitude using a combination of infrared and ion sensors.

The SKDU engine ignited at 12:29:04 Moscow Time and fired until 12:35:39 Moscow Time, reducing the ship's velocity by 105 meters per second.

The descent module then separated at 12:45:08 Moscow Time and appeared in view of the IP-16 station in Crimea at 12:46:44 Moscow Time.

The opening of the main parachute then took place at 13:01:09, followed by the landing at 13:13 Moscow Time. According to the Soviet air defense services, the landing point had coordinates of 52 degrees 17 minutes North latitude and 71 degrees 42 minutes East longitude. It was 145 kilometers from the city of Pavlodar.

The weather at the landing site apparently repeated itself on April 20, 1968. (231) Winds were reaching 25 meters per second in the area. Again, the search and rescue teams zeroed in on the descent module while it was still in the air, but, for a long while, a strong dust storm prevented the helicopters from dropping the recovery personnel at the touchdown site.

Nevertheless, on April 20, the first descent module arrived at Tyuratam aboard an An-12 transport plane and after a preliminary inspection by specialists, the capsule proceeded to Moscow. By all accounts, the second Soyuz docking mission was a complete success, (820) however it was only in 1985 that an official Soviet publication identified Kosmos-212 and -213 as unmanned Soyuz spacecraft. (2)

 

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The article and illustrations by Anatoly Zak; Last update: April 22, 2018

Page editor: Alain Chabot; Last edit: April 16, 2018

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assembly

Soyuz 7K-OK spacecraft under assembly in Tyuratam.


rendezvous

A Soyuz 7K-OK spacecraft during a rendezvous in orbit.