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Propulsion system


"Black Box"

The author would like to thank Gert Sassen for his help in preparing this section.


Soyuz MS-10 makes emergency landing after a launch failure

The launch of the Soyuz MS-10 at 4:40 a.m. EDT on Oct. 11, 2018, ran into a "booster problem" near the time of the first-stage separation around two minutes after liftoff, sending the spacecraft into a "ballistic reentry mode," according to NASA. Rescue helicopters lifted off from Baikonur in the direction of the projected emergency landing site between 3:51 and 3:55 a.m. Houston time and were expected to reach the site in 1.5 hours, NASA said. Around 5:20 a.m. EDT (or less than half an hour after launch), NASA reported that rescue services were in radio contact with the crew on the ground east of Dzhezkazgan in Kazakhstan following a ballistic reentry and landing. The crew was reported to be in good condition.

Previous mission: Soyuz MS-09

Released on Nov. 1, 2018, this view is from an onboard camera during the launch of the Soyuz MS-10 spacecraft on Oct. 11, 2018, however a number of crucial frames from the footage appeared to be missing.

Soyuz MS-10 mission at a glance:

Spacecraft designation Soyuz MS-10, 11F732 No. 740, ISS mission 56S
Crew Aleksei Ovchinin (Roskosmos), Nick Hague (NASA)
Spacecraft mass ~7,220 kilograms
Launch vehicle Soyuz-FG
Launch site Baikonur, Site 1
Launch date and time 2018 Oct. 11, 11:40:15.539 Moscow Time (4:40 a.m. EDT)
Docking date and time 2018 Oct. 11, 17:44 Moscow Time (10:44 a.m. EDT) (planned)
Destination and docking location ISS, Russian Segment, MIM-2 Poisk module (planned)
Flight duration Actual: 19 minutes 41 seconds; Planned: 187 days (Six months)
Landing date Actual: 2018 Oct. 11; Planned: 2019 April 15
Mission status Launch failure; Descent Module makes emergency landing, saves the crew
Maximum altitude reached 93 kilometers on a suborbital trajectory
Landing location 32 kilometers southeast of Dzhezkazgan, Kazakhstan
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Launch mishap caught on camera


The live broadcast of the launch appeared showing multiple debris separating from the rocket around two minutes after the launch, when the four boosters of the first stage were supposed to drop. A moment earlier, the anomaly was preceded by a "puff" in the exhaust stream, which some interpreted as a sign of the impending failure, but, more likely, it was a signature of the main escape rocket separating from the launch vehicle, which is often observed in piloted launches. A camera inside the capsule also showed apparent violent jolts of the spacecraft around the same time (at 1 min. 59 sec. in flight (T+119 seconds)), even though they are not uncommon for staging events.

There was also a short message from ground control about a booster failure at T+165 seconds in flight. The crew members were also heard describing weightlessness, while they were supposed to experience acceleration. However Roskosmos continued twitting routine launch milestones during the entire nine-minute ascent sequence and announced the successful separation of the spacecraft from the third stage into orbit.

Shortly before 6 a.m. EDT, NASA reported that Roskosmos had formed a State Commission to investigate the incident, but had planned no press conference on the matter at the time.

Search and rescue operations



Descent Module of Soyuz MS-10 after landing.

Around 6:10 a.m. EDT on October 11, NASA reported that the crew was out of the capsule and that rescue personnel had reached the landing site, assisting the crew with post-landing operations.

According to TASS, quoting a statement from the Central Military District, TsVO, whose personnel was responsible for search and rescue, the PEM-1 amphibious vehicle was used to turn the capsule in order to free the ship's blocked forward hatch before the crew could be extracted.

TsVO's An-26 aircraft dropped military parachutists at the site, who reached the spacecraft before the arrival of the helicopters. Medics examined the crew and found them in a satisfactory condition, TASS said. Aircraft and ground vehicles based in Dzhezkazgan, Baikonur and Karaganda initiated search operations soon after the accident. Within an hour, four Mil-8 helicopters and a ground-based team reached the Descent Module.


Members of the Soyuz MS-10 crew at the Dzhezkazgan airport soon after their emergency landing.

At 7:10 a.m. EDT, NASA announced that the crew had been onboard a helicopter heading to Dzhezkazgan. The crew was then picked up by a plane in Dzhezkazgan and flown to Baikonur's Krainy airfield. The Russian cosmonaut Aleksei Ovchinin was expected to arrive at the Chkalovsky airfield near Star City before the end of the day, but, later, it had been decided to keep the crew in Baikonur for medical checks until the morning of October 12 before another flight to Moscow.

The ISS crew was informed that Soyuz MS-10 had landed near the town of Karazhal in Kazakhstan, after experiencing an acceleration of around 6.7 g. According to Russian sources, the landing site was located 25-30 kilometers east of Dzhezkazgan (around 400 kilometers downrange from the launch pad).

After the departure of the crew from the landing site, specialists from Roskosmos and RKK Energia, the spacecraft manufacturer, concluded recovery operations with the capsule.

Head of emergency services in Kazakhstan Vladimir Bekker was quoted by RIA Novosti news agency as saying that 24 Russian teams had been dispatched to search for debris from the accident. Bekker said that there had been no reports of injuries or property damage from the accident, which had taken place away from populated areas.

In the meantime, by October 13, additional medical checks conducted immediately after the landing of the crew near Moscow confirmed that Ovchinin and Hague had been in excellent physical shape after their ordeal, not withstanding some reports in the Russian media.

Restoring the Soyuz MS-10 failure and escape events


The graphic released by Roskosmos on Nov. 1, 2018, provides the Soyuz MS-10 accident timeline, but it was questioned on the forum of the Novosti Kosmonavtiki magazine. According to a poster, who was familiar with the data of the Onboard Recording System, SZI, the firing of the soft-landing engines of the Descent Module, SA, (taking place at touchdown) was recorded at T+1,180 seconds from the activation of the SZI, which was supposed to be operating at liftoff. Therefore, the actual flight could not be longer than 1,180 seconds.

According to Deputy Prime Minister Yuri Borisov, quoted by TASS soon after the accident, the emergency escape system was activated at T+123 seconds in flight. As a result, the escape began after the separation of the emergency rockets (at T+114.6 seconds) and the first stage at T+117.80 seconds at an altitude of around 50 kilometers.

A few hours after the accident, RIA Novosti quoted industry sources as saying that telemetry analysis had pointed toward a possible pyrotechnics separation problem between the first and second stage. According to industry sources quoted on the Novosti Kosmonavtiki web forum, the pressurization valve on one of the strap-on boosters of the first stage failed to open as scheduled to push it away from the second stage during separation and it led to the empty booster's tip slicing open the second stage. According to Interfax, the impact of the first-stage booster caused the rupture of a (propellant tank) on the second stage and the loss of attitude control (of the entire vehicle). (Under normal circumstances, the nozzle of the oxidizer tank pointed 45 degrees relative to the main axis of the strap-on booster, generates reverse trust upon opening of the valve.)

Images available from the BSVK video system confirmed abnormal behavior of the D strap-on booster of the first stage with the failed oxidizer valve.

The accident took place during a phase of the flight, known as No. 1A, extending from the separation of the main escape rocket to the separation of the payload fairing protecting the spacecraft from aerodynamic loads. During that period, the propulsive role in ejecting the spacecraft from a failing rocket shifts to four solid motors, RDGs, attached to the payload fairing. One pair of these motors is activated on the emergency command and the other two engines fire 0.32 seconds later.

The failure command is issued on the basis of the data from angular velocity sensors on the second and third stages of the rocket. When those sensors detect a deviation of the vehicle exceeding seven degrees on the second stage or 10 degrees on the third stage, they generate an "avariya" (accident) command, which triggers the emergency escape sequence. However, after the separation of the four boosters of the first stage, the emergency escape scenario has a six-second pause to allow the firing core booster of the second stage to stabilize its flight after the somewhat violent separation process.

As a result, on Soyuz MS-10, following the "avariya" signal, which was displayed on the crew's console in the cockpit, four RDG motors were activated and pulled the payload section, OGB, including the Descent Module with the crew and the Habitation Module, away from the rocket, at T+122 seconds. Next, at T+160 seconds, the Descent Module was separated from the OGB stack and the capsule with the crew then entered free fall, heading for reentry into the Earth's atmosphere. Around that time, the crew (on the advice from mission control) activated the ballistic descent mode. The successful touchdown of the capsule took place 19 minutes 41 seconds after liftoff, 32 kilometers southeast of Dzhezkazgan. At its highest point, the Descent Module reached an altitude of 93 kilometers. However, mission control in Houston had some period of communications blackout, which obviously racked some nerves on the ground.


A European astronaut Alexander Gerst captured the failed Soyuz launch from the ISS. The photo is likely taken shortly after the separation of the escape section from the rocket.

The Astra diagnostics system

According to plans approved during 2017, the Soyuz MS-10 spacecraft was supposed to be the first within the Soyuz MS series to be equipped with a new telemetry system, which could be a great help in the investigation of the mishap. The new Astra avionics unit was expected to replace the originally planned Skut-40 system to monitor extremely fast-changing parameters during the ascent to orbit and the separation of the spacecraft from the launch vehicle. The installation of the Astra telemetry system, developed at NPO IT in Korolev, was ordered in the wake of the previous launch accidents with the Progress cargo ships. It was a part of a wider plan to thoroughly analyze flight dynamics of the Soyuz rockets carrying transport ships in order to prevent related accidents. The Progress MS vehicles were also promised to be equipped with the Astra telemetry system starting with the Progress MS-10 mission. The Astra system was also tested aboard the ill-fated Soyuz-2-1b rocket launched from Vostochny on Nov. 28, 2017.

Along with the Astra system, the transport ships would also receive its own network of sensors to measure impacts and vibrations during the flight, however, in order to digest a great deal of data coming from the new measuring network, the ship's flight control system and its software would have to be upgraded accordingly.

Only on Dec. 12, 2018, did AO RKS Corporation, the parent company of NPO IT, confirm that the Astra had indeed been aboard the Soyuz MS-10 spacecraft, but the new telemetry system had never had a chance to operate due to a launch abort.

Investigation looks into the Soyuz MS-10 launch accident


View of the Soyuz MS-10 launch at the time when the first stage was supposed to separate.

In the evening of October 11, a Kazakh search team located a half of the payload fairing from the aborted launch of the Soyuz MS-10 spacecraft around 40 kilometers from the town of Dzhezkazgan. The fragment was then transferred to Roskosmos.

Next day, TASS, quoting Nursultan Nurakhmetov, an official from the Kazakh emergency services, reported that search team from a Russian debris utilization base No. 1 in Dzhezkazgan had located remnants of the first, second and third stages of the failed Soyuz-FG rocket, as well as the emergency escape rocket, in the Karaganda Region of Kazakhstan. The were spread over a 40-kilometer area near the Talap village of the Ulytaus District. There were no fires or damage at the sites, according to Nurakhmetov.

At the same time, RIA Novosti reported that the Descent Module was delivered to RKK Energia in Korolev and specialists began deciphering its data, planning to provide a preliminary report to the management by the end of the day on October 12.

According to TASS, the investigative commission was given two weeks for its work and was originally expected to provide its findings by October 25, 2018. The commission reportedly included military officials, because Soyuz family of launchers was used for missions of the Ministry of Defense. Roskosmos announced that the commission would begin work at RKTs Progress in Samara, the manufacturer of the Soyuz rockets, at the beginning of the following week (starting October 15). The recovered fragments of the Soyuz-FG rocket arrived at RKTs Progress on October 14. Investigators planned to arrange the recovered debris along the outline of the original boosters inside one of the processing halls. Around the same time, the Descent Module was delivered to RKK Energia in Korolev.

The next day, the commission began its work in Samara. The investigators quickly focused on the sensor failure in the separation mechanism between the first and second stage, which resulted in the lack of signal to open the pressurization valve on the reverse thrust nozzle of the D booster. The circumstances of the accident were considered to be similar to those during the launch of a Soyuz-U rocket on March 26, 1986, when the sensor shaft, believed to be damaged during the assembly of the rocket, failed to exit its housing during the separation, thus preventing the device from generating the opening command to the pressurization valve on the reverse thrust nozzle.

On October 17, Head of Roskosmos Dmitry Rogozin chaired a meeting of the investigative commission at RKTs Progress.

Several experiments with the separation system between the first and second stages were also planned to confirm the work of the investigative commission, which delivered its preliminary report on the accident on October 20 during a meeting at the TsNIIMash research institute in Korolev. According to Roskosmos, the final report and recommendations for corrective measures to the industry would be delivered to the Chairman of the State Commission overseeing flight testing of piloted space systems on Oct. 30, 2018.

Roskosmos completes the investigation

On Oct. 31, 2018, Roskosmos State Corporation confirmed that the separation sensor failure had caused the accident. In the follow-up press-conference at TsNIIMash research institute and in the official statement published on November 1, Roskosmos said that the abnormal separation of the D booster was caused by a bending deformation of a sensor rod by 6º45' degrees during the assembly of the launch vehicle at the Baikonur launch site. The damaged sensor prevented the opening of the cover on the reverse-thrust nozzle of the booster, which led to its impact on the core stage.

The cause of the accident was characterized as operational and affecting only Soyuz vehicles, which underwent final assembly.

The November 1 press-release quoted Deputy Director General at TsNIIMash Oleg Skorobogatov (who led the interagency investigative commission) as saying that the "launch concluded with a failure of the launch vehicle due to abnormal separation of one of the side boosters (Block D), whose nose section hit the core stage (Block A) in the area of the fuel tank, which led to its depressurization and the loss of stability of the launch vehicle."

According to Skorobogatov, during the botched separation, the booster was initially sliding along the inverted cone at the top of the core booster, before hitting its fuel tank below.

An onboard video also released on November 1 clearly showed the impact of the booster, the severe damage to the second stage, the massive venting of the propellant and the wild gyration of the rocket.

Impact of the accident on ISS operations

In the hours following the launch abort, NASA officials were not able to say much about how the accident would affect further ISS operations besides the fact that the transport spacecraft then docked at the station (Soyuz MS-09) had a guaranteed life span until January 2019. According to NASA, the station had plenty of supplies and could operate without crew if necessary, though the agency would prefer to avoid it. (Russia successfully operated the ailing Mir space station without crew onboard for several prolonged periods of time, though not without problems.)

NASA also had to put on hold its plans for a spacewalk by Alexander Gerst and Nick Hague, who were trained to replace a set of batteries for the station's solar arrays. Roskosmos did the same with the plan for its spacewalk conducted by Aleksei Ovchinin, which had a task to investigate a mysterious hole aboard Soyuz MS-09, among other tasks. Upon the return of Hague and Ovchinin to Star City on October 12, Roskosmos head Dmitry Rogozin announced that there had been plans for their (second) flight in the Spring of 2019.

Within days after the failure Roskosmos envisioned the following timeline for the return to flight of the Soyuz rocket family and the resumption of the ISS missions:

Crew re-arrangement


Dressed in pressure suits, two members of the Soyuz MS-10 crew comprised of Roskosmos cosmonaut Aleksei Ovchinin (left) and NASA astronaut Nick Hague familiarize themselves with their flight-worthy vehicle during the ship's processing at Site 254 in Baikonur on Sept. 26, 2018.

According to early flight manifests, the launch of Soyuz MS-10 was scheduled on September 14, but by June 2018, it was re-scheduled for October 11. Also, the original crew of the mission included Aleksei Ovchinin, Nikolai Tikhonov and Nick Hague, however by April 2018, rookie cosmonaut Nikolai Tikhonov was dropped from the crew, due to continuous delays with the launch of the MLM Nauka module.

Roskosmos apparently considered options for launching a commercial passenger on that flight, but ultimately decided to launch a crew of two, accompanied by 62 kilograms of extra cargo, which was comprised of five containers with food and other supplies, including a 3D bio-printer and its production materials.

However on its way back to Earth in April 2019, Soyuz MS-10 was expected to carry a commercial passenger from the United Arab Emirates, who was slated to arrive at the station aboard Soyuz MS-12 for a short visit.

Preparations for launch

On March 28, 2018, RKK Energia announced that Russian cosmonauts Nikolai Tikhonov and Andrei Babkin had participated in the so-called fitting tests of the Soyuz MS-10 spacecraft, which at the time, was undergoing final assembly at the company's facility in Korolev. Along with engineers, the cosmonaut pair conducted inspection and checks of the equipment aboard the vehicle and familiarized themselves with the placement of internal cargo, which was represented with simulators, RKK Energia said.

The flight-worthy Soyuz MS-10 arrived at Baikonur launch site on June 5, 2018, but active preparations for the mission did not begin until the following month. On the evening of July 4, the vehicle was transferred from the echoless chamber at Site 254 to its pre-launch processing stand inside the same building, after a day-long testing of its Kurs rendezvous system and other radio equipment aboard it. Between July 13 and July 19, the spacecraft was undergoing testing inside the vacuum chamber and on July 20, RKK Energia announced that test activations of all systems and integrated tests had been completed, and after placing all its components into the folded position, the spacecraft had been left in the storage mode.

On August 15, Roskosmos announced that the Soyuz-FG rocket for the Soyuz MS-10 mission was under assembly in Baikonur. The photos released at the time showed the integration of the two main components of the core stage and the subsequent attachment to it of the four strap-on boosters.

On September 25, the primary and backup crew of the Soyuz MS-10 spacecraft arrived at Baikonur for the final phase of training, including a practice inside the flight-worthy vehicle, which was conducted the next day.


The Soyuz MS-10 is lowered in horizontal position for integration with the payload fairing inside the spacecraft processing building at Site 254 in Baikonur on Oct. 3, 2018.

The spacecraft was then sent for fueling with propellant and gases and returned to the processing building on September 29. On October 1, the spacecraft was integrated with an adapter ring, which would connect it to its Soyuz-FG rocket. On October 3, RKK Energia specialists conducted the final visual inspection of Soyuz MS-10 and rolled it inside its protective fairing. The final familiarization training by the primary and backup crew inside the flight-worthy spacecraft, but without pressure suits was conducted on October 6, before its transfer the same day to the vehicle assembly building at Site 112 for integration with its rocket.

On the morning of October 9, the Soyuz-FG launch vehicle with the Soyuz MS-10 spacecraft was rolled out to its launch pad at Site 1 and installed in vertical position.

Launch profile


Soyuz MS-10 is being erected onto the launch pad at Site 1 on Oct. 9, 2018.

The liftoff of a Soyuz-FG rocket with the Soyuz MS-10 (No. 740) transport spacecraft was scheduled for Oct. 11, 2018, at 11:40:15 Moscow Time (4:40 a.m. EDT) from Site 1 in Baikonur. The vehicle carried a crew of two from Baikonur toward the International Space Station, ISS.

At the time of launch, the station was flying over north-eastern Kazakhstan at an altitude of 254 statute miles. The spacecraft was assigned to attempt a four-orbit, six-hour rendezvous profile with the station, concluding with an automated docking at the MIM2 Poisk module, a part of the Russian Segment of the ISS on the day of the launch at 17:45 Moscow Time (10:45 a.m. EDT). Following leak checks, the hatches between the spacecraft and the station were expected to open between 12:45 and 13:10 Moscow Time (12:45 - 1:10 p.m. EDT).

At the time of the launch, the Soyuz MS-10 and its crew was expected to stay aloft for 178 days and return to Earth on April 15, 2019.


Soyuz MS-10 crews:

Primary crew Backup crew
Aleksei Ovchinin (Roskosmos) Oleg Kononenko (Roskosmos)
Nick Hague (NASA) David Saint-Jacques (CSA)


This page is maintained by Anatoly Zak; Last update: February 17, 2023

Page editor: Alain Chabot; Last edit: October 11, 2018

All rights reserved


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Andrei Babkin (left) and Nikolai Tikhonov familiarize themselves with Soyuz MS-10 spacecraft during its final assembly at RKK Energia in Korolev on March 28, 2018. Click to enlarge. Credit: Roskosmos


Soyuz MS-10 is being prepared for transfer to its processing stand after completion of radio tests on July 4, 2018. Click to enlarge. Credit: Roskosmos


The assembly of the Soyuz-FG rocket for the Soyuz MS-10 mission in August 2018. Click to enlarge. Credit: Roskosmos


The crew of the Soyuz MS-10 spacecraft arrives at Baikonur on Sept. 25, 2018, for a final training before the October 11 launch. Click to enlarge. Credit: Roskosmos


The primary crew of the Soyuz MS-10 spacecraft dressed in pressure suits, including NASA astronaut Nick Hague and Roskosmos cosmonaut Aleksei Ovchinin, walk to their flight-worthy vehicle during the ship's processing at Site 254 in Baikonur on Sept. 26, 2018. Click to enlarge. Credit: Roskosmos


The Soyuz MS-10 spacecraft is being prepared for integration with its launch vehicle adapter inside the spacecraft processing building at Site 254 in Baikonur on Oct. 1, 2018. Click to enlarge. Credit: Roskosmos


The Soyuz MS-10 primary and backup crews conduct the second and final training inside their flight-worthy spacecraft undergoing final processing at Site 254 in Baikonur on Oct. 6, 2018. Click to enlarge. Credit: Roskosmos


Soyuz MS-10 inside its payload fairing (top) departs the spacecraft processing building at Site 254 for a trip to vehicle assembly building at Site 110 on Oct. 6, 2018. Credit: RKK Energia


Soyuz MS-10 lifts off on Oct. 11, 2018. Click to enlarge. Credit: NASA


Crew during ascent to orbit aboard Soyuz MS-10. Click to enlarge. Credit: Roskosmos


Several crucial frames showing the breach of the second stage captured by an onboard video camera, ended up missing from the official footage released on Nov. 1, 2018. Click to enlarge. Credit: Roskosmos


Descent Module of Soyuz MS-10 at the landing site. Click to enlarge. Credit: Roskosmos


Relatives greet members of the Soyuz MS-10 crew at their return to Baikonur following the launch accident. Click to enlarge. Credit: NASA


Remnants of the Habitation Module of the Soyuz MS-10 after their return to the spacecraft processing building at Site 254 in Baikonur. Credit: Novosti Kosmonavtiki

Staging process

A separation sequence between strap-on boosters and the core stage of the R-7 rocket. Click to enlarge. A: Severing of lower connections, as all stages are still thrusting and pivoting of strap-on boosters around upper connectors. B: Upon reaching a certain rotation angle, upper connectors disengage, releasing boosters; oxidizer pressure valves open on boosters for retro thrust. V: Boosters fall away from the core stage, which continues a powered flight. Credit: Moscow Aviation Institute


Astra telemetry system. Credit: AO NPO IT


Acting Director General at RKTs Progress Dmitry Baranov (left) and Roskosmos Head Dmitry Rogozin inspect the hinge mechanism at the tip of the first stage booster interfacing with the separation system on the second stage of the Soyuz rocket. Investigators suspected that a sensor mechanism at that location failed to send a command to open pressurization valve on the reverse thrust nozzle (visible at the bottom), which guarantees clean separation. Click to enlarge. Credit: Roskosmos


A photo of the damaged sensor shown on Oct. 31, 2018, which was determined to be a culprit in the October 11 accident. Credit: Novosti Kosmonavtiki