Soyuz-1 attempts to return to Earth
Despite numerous challenges, Vladimir Komarov with the help of engineers on the ground, was able to overcome all the technical problems in orbit and successfully piloted his spacecraft on a path back to Earth in the early hours of April 24, 1967.
Soyuz-1 in orbit.
April 24: The reentry
As Soyuz-1 began its 17th orbit, the SKD engine was scheduled for fire for 146 seconds beginning at 02:56:12 Moscow Time on April 24. The separation of the descent module was expected to be confirmed with the appearance of a signal from the capsule's UHF transmitter at 03:08 Moscow Time, before its subsequent disappearance at 03:15.
If everything went as scheduled, the parachute would be released at 03:21 Moscow Time, followed by the touchdown at 03:36 Moscow Time, 150 kilometers east of Karaganda. (774)
However, at the expected time, the ground control station in Crimea tracking the flight, determined that the spacecraft's trajectory had not changed and it had not been following the projected reentry path. Komarov soon resumed communications, explaining that he had initially succeeded in establishing attitude control of the spacecraft with the use of ion sensors, however somewhere near the Equator (on the night side of orbit, according to Mishin (774)), the vehicle deviated from proper attitude and the flight control system blocked an upcoming firing of the SKD engine.
According to Chertok, flight managers rushed to plan another attempt on the 18th orbit, however as Soyuz-1 went out of range, no new instructions had been sent to Komarov. (466) Mishin, however, describes uploading the descent sequence for the daylight part of the orbit with the reliance on the VSK periscope, whose data could be used for providing approximate guidance to gyroscopic instruments. However, this new sequence was rejected because of a conflict with Sequence No. 3, which had programmed the spacecraft to begin spin stabilization to the sun. (774)
In any case, the new reentry attempt was now moved to orbit 19. It called for Komarov to manually orient the spacecraft during the orbital daylight, then, when it enters night side of the orbit, a reliable KI-38 gyroscopes would maintain the attitude control. As the spacecraft would emerge from the shadow, Komarov could again correct the orientation manually, while the Soyuz would go through the reentry sequence during the 19th orbit. In the meantime, Yablokova, a chief engineer responsible for power supply, approached Chertok. She warned him that available resources of the primary battery would work for another orbit or two and the backup battery would supply power for three more orbits.
As the new communications period started, Gagarin relayed Komarov latest instructions, which included:
According to Chertok, Komarov had never practiced that particular scenario, but promised to do as planned. Mishin also discussed the proposed sequence with Komarov, who again expressed his confidence in the operation. Mishin recorded the following timeline for the descent:
Landing point was expected at 58 degrees East longitude and 51.30' North latitude. (774)
Next opportunity to hear from Komarov came during the descent itself. By that time, communications were coming via a small antenna in the reentry capsule, since Soyuz-1 had already gone through separation of its main sections.
Komarov reported that the braking engine had been cut off at 05:59:38.5 Moscow Time after firing for 146 seconds. At 06:14:09, the Failure-2 command interrupted the nominal descent. Komarov's words then drowned in the background noise.
Boris Raushenbakh, who was responsible for the flight control, explained that because of the asymmetrical shape of the spacecraft with only one solar panel open, attitude control thrusters were not able to maintain proper orientation long enough for the entire duration of the braking maneuver. As a result, the gyroscope generated Failure-2 command when the deviation from the nominal attitude exceeded eight degrees. However Raushenbakh also had a good news: the braking maneuver was long enough to guarantee the reentry into the Earth's atmosphere.
In the aftermath of the Failure-2 command, the attitude control system of the reentry capsule was turned off. As a result, the reentry capsule was descending on a ballistic trajectory, without an aerodynamic lift which would be possible during the nominal landing profile. (27)
As a result of the ballistic reentry, which shifted the landing site for the Soyuz forward, a backup recovery and rescue team, (deployed in the city of Orenburg) would be responsible for the landing. It included a technical team from TsKBEM led by E. P. Utkin. (52)
At 06:22, the Soviet anti-aircraft radar detected the reentry capsule. It was projected that the Soyuz-1 would land 50 kilometers east of Orsk at 06:24 on April 24, 1967.
Personnel in Crimea had never received a confirmation about the successful landing. Chertok's description of the fateful morning mentions Gagarin's fruitless efforts to penetrate paranoid secrecy of the Soviet military in order to get any news about Komarov. (27)
Read much more about the history of the Russian space program in a richly illustrated, large-format glossy edition:
Komarov inside the Soyuz simulator. Credit: RKK Energia