Ninety Millimetres From Salyut

On the morning of their second day in space, the Soyuz 10 crew performed systems tests in preparation for the final manoeuvre, which was achieved as planned. When their trajectory brought them within 16 km of Salyut the Igla automatic rendezvous system was activated. When the radar had locked onto the station's transponder the Igla began to steer Soyuz 10 towards its target, with the crew as mere spectators.

Just before midnight on 24 April the control room at the TsUP-E was so crowded that late arrivals had to stand. The GOGU members were seated, as was Popovich at the communications system, but squeezed in around the table, some seated but most standing, were the TsKBEM managers, representatives of the other design bureaus involved in the mission, generals, politicians and members of the State Commission. One of the most anxious was Armen Mnatsakanyan, the Chief Designer of the Igla. This had failed when Soyuz 8 had attempted to rendezvous with Soyuz 7 in October 1969. He had been criticised by the Kremlin, but not punished.

The final phase of the rendezvous had been timed to occur over the Soviet Union, in order to have 'live' communications, but the loudest voices in the control room were those of Mishin and General Kerimov, demanding explanations of events from the members of the GOGU, including wishing to know what would be done if the Igla were to fail!

''Approaching; Soyuz is two seconds in front of the Salyut!''

''Why do you give us seconds? Give kilometres!"

''Granite reports radio lock-on achieved. Igla works!''

General Agadzhanov, the head of the GOGU team, lost concentration and shouted into the microphone: ''We understood you - the distance is 10 kilometres. Do not interfere!'' In fact, only the first part was intended for the cosmonauts; his directive not to interfere was directed at Mishin and Kerimov, whose interminable calls for explanations were interfering with the work of the controllers, but

Agadzhanov still had the microphone keyed when he spoke these words. The cosmonauts, having no idea of the state of the control room, expressed surprise: "We only reported on the progress of our approach, according to the indicators on the command panel."

One of controllers complained, saying that it would be a miracle if he survived the morning without suffering a heart attack.

General Kerimov, ignoring Agadzhanov's direction, again demanded information. Struggling to remain calm, Agadzhanov offered an apology to the crew: "Igla works, understood! This is to Granite. Distance 11 kilometres. The rest was to our guests!'' On hearing of the increased range, Mishin exclaimed: "How! Firstly 10, now 11? Who is guilty?''

Ignoring Mishin's question, Agazdhanov spoke a series of sentences, some to the crew and others to inform the people in the control room: "The DOS engine started! Granite reports about the work of its engine. The programme for the 81st orbit has been executed. The DOS engine worked for 60 seconds. I'm No. 12: Granite, on the 82nd orbit we await from you the most important reports about the operation of the Igla and the automatic approach.''

"Why do you speak so much?'' demanded Mishin angrily. Somebody attempted to calm Mishin by explaining that Agadzhanov was at the same time communicating with the cosmonauts and serving as commentator for the audience.

"Engine works 20 seconds; 25 seconds; 30 seconds; 35 seconds; 40 seconds; 45 seconds.''

"Why don't they turn it off themselves?"

"The approach speed is 8 metres per second; steady radio lock-on." "We see a bright point. Distance 15 kilometres, speed 24.'' "Please! Silence in the room!''

"Who will explain to me why they were at 11 kilometres and now the distance is 15? Chertok, Mnatsakanyan, Raushenbakh - why do you sit and do nothing?'' "Igla is working,'' Mnatsakanyan told Mishin.

"This is a mad house! Only Igla does not go mad,'' said Raushenbakh quietly. Fortunately, the chaos in the control room was not matched in space. Soyuz 10 continued its automatic approach without any glitches. "Distance 11, speed 26.5,'' reported the crew.

"Distance 8, speed 27.5; distance 6, speed 27. DPO light. Starting to turn.'' At this point Mishin exclaimed: "It can't approach at that speed! Why do you do nothing? Tell the crew what to do!''

Knowing that the rate of closure was according to plan, Raushenbakh explained to Mishin: "It isn't necessary to intervene, it will brake now.''

The spacecraft had turned and started its braking sequence. The crew continued to report the closure parameters.

"Distance 4, speed 11. We can see the target against the background of the Earth - its flashing navigation lights. Distance 2.5, speed 8.''

The medical telemetry showed that the heart rates of Shatalov and Yeliseyev were 100 beats per minute; Rukavishnikov, less active, was only 90 beats per minute.

At 1,600 metres from Salyut the speed was 8 metres per second. At 1,200 metres it had slowed to 4 metres per second. At a distance of about 1,000 metres, the crew could see the station in the optical periscope.

With the approach going smoothly, the mood in the control room improved.

"Distance 800, speed 4."

A few seconds later: "I see the target well and distinctly."

At this point the spacecraft passed out of range of the last station in the chain that stretched across Soviet territory, leaving the people in the control room in a state of apoplexy during the 30-minute wait for the next communications opportunity.

Mishin demanded an explanation from Raushenbakh for why the docking had not occurred while over Soviet territory. Instead of answering, Raushenbakh noted that Soyuz 10 had consumed 80 kg of fuel in making the approach - almost twice the amount planned! When no one appeared to appreciate the implication, Raush-enbakh pointed out that if Shatalov failed to dock at the first attempt, the fact that 45 kg of fuel would be required for the descent meant that there would be insufficient to set up a second approach, and the crew would have to prepare for an immediate return to Earth.

Meanwhile, the Igla continued to steer Soyuz 10 towards its target. At 500 metres the approach speed was just 2 metres per second. Never before had any spacecraft approached such a large vehicle in space.

Shatalov recalls: "All the dynamic operations of the ship were conducted without any problems. The only issue appeared at the time that the Igla took control of the approach: the ship would oscillate from side to side periodically, requiring the firing of the correction engines. At a distance of 150 metres I took manual control. It was simpler than on the Soyuz 4 mission. The station grew bigger and bigger - in space, it appeared to be much larger than it had on the ground! When we were very close, Aleksey and Nikolay carefully inspected its docking mechanism, antennas and solar panels."

The final approach was at about 30 cm per second. When the probe on the front of the Soyuz came into contact with the conical drogue of Salyut, the cosmonauts saw the Mechanical Connection indication on their instrument panel. The docking process was automatic, and the crew had only to monitor their instruments as the spacecraft slowly advanced in order to drive the head of its probe all the way into the drogue. There were some vehicle motions, and a scraping noise as the probe slide across the drogue. The probe engaged the mechanism at the apex of the drogue, and began to retract to draw together the two annular collars in order to establish a hermetic seal. The cosmonauts awaited the signal that would indicate that the retraction process was complete. Instead, a warning signal came on to indicate that the mechanism had stalled. How could this be? What had happened?

When Soyuz 10 flew into the next communication zone, Shatalov heard an eager call from Earth, and reported: "I am Granite, I hear you well! At 4 hours 47 minutes we made a manual approach. Contact and mechanical capture passed. The retraction began. But in the 9th minute the SSVP stopped. Retraction not completed. Docking not achieved. We don't understand why. Look at the telemetry. Let us know what to do.''

Soyuz Ssvp

The active docking probe of the Soyuz (left) and the passive docking cone of the Salyut (centre). The diagram shows the lever on the probe of Soyuz 10 believed to have been damaged. At the top of the pin (1) of the probe is the head (2), which is inserted into the nest (3) of the cone (8). On the sides of both docking mechanisms are the connectors for electrical (13) and hydraulic (4) links between two vehicles. The shock absorber (12) is on the base of the probe. (Diagram courtesy Sven Grahn)

The active docking probe of the Soyuz (left) and the passive docking cone of the Salyut (centre). The diagram shows the lever on the probe of Soyuz 10 believed to have been damaged. At the top of the pin (1) of the probe is the head (2), which is inserted into the nest (3) of the cone (8). On the sides of both docking mechanisms are the connectors for electrical (13) and hydraulic (4) links between two vehicles. The shock absorber (12) is on the base of the probe. (Diagram courtesy Sven Grahn)

Everyone in the control room turned in silent expectation to the people who had designed the docking system. Pale faced, Vsevolod Zhivoglotov, a member of that team, explained that the active probe had touched the cone of the drogue according to plan. The length of the probe was 390 mm in its fully extended state. It started to retract, but when the length was down to 90 mm the mechanism was automatically commanded to halt. To the amazement of all concerned he explained eight things that could have gone wrong, including the possibility that one of the lateral levers of the probe had broken off - and he said that a pronounced swinging action just after capture strongly suggested that this had occurred.

Mishin exploded: ''Why swinging? What are the dynamics? Raushenbakh! Why were there fluctuations?''

Cosmonaut Popovich, who had continued to talk with the crew, told Chertok that Yeliseyev had just reported that during the retraction process the orientation engines had been firing, causing a strong motion of the ship. For Chertok this was sufficient to indicate what had happened: ''It is most probable that the mechanical breakdown occurred because of the large transverse oscillations - we didn't turn off the control system!'' As the probe penetrated the drogue, the spacecraft had been deflected and the control system had tried to eliminate the angular deflections. However, the ship was no longer free to manoeuvre, and instead of rotating about its centre of mass, as the control system expected, it swung on the end of the probe and this broke part of the mechanism. In conclusion: ''To continue the docking attempt will be futile. We must make a decision about the undocking.''

As Shatalov recalled of these dramatic moments: ''Just after the capture, the ship swung to the right by 30 degrees, and then to the left. The period of oscillation was seven seconds. We were concerned that we might lose the docking mechanism. We didn't know why this was occurring during the retraction operation. We approached the station with almost no difference between the axes of the ship and the station, so such motions ought not to have happened.'' The continuous firing of the orientation engines consumed a lot of fuel. "Before docking, the pressure in the tanks was 220 atmospheres, and it was only 140 when the operation automatically terminated. It is unbelievable how much fuel was consumed during this period."

Soyuz 10 was connected to Salyut only by small latches gripping the head of the probe. The disappointed crew were told to do nothing until the next communication session. Meanwhile, the engineers at the TsUP assessed the situation. The next time that the orbital complex appeared over Soviet territory Rukavishnikov was asked to enter the orbital module and check the electrical contacts of the docking mechanism to ensure that the retraction had not been halted by a faulty signal - since if that was the case the docking probe might not have been damaged at all, and the retraction should be able to be resumed. Rukavishnikov was fully familiar with the system. He removed a cover to access the electronics of the docking system, and confirmed that all of the connectors were as they should be. That was the last hope.

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