The launch of the Soyuz MS-23 rescue ship

For the second time in history, an unmanned Soyuz is being launched to replace another in orbit. On February 24, 2023 at 00:24:29.5 UTC, a Soyuz-2.1a rocket (serial number М15000-060) lifted off from the PU-6 ramp (named Vostok “east” in Russian) from District 31 of the Baikonur Cosmodrome (Kazakhstan). On board was the Soyuz MS-23 spacecraft (11F732A48 No. 754), also called 69S in NASA’s internal classification. The Soyuz MS-23 was unmanned because its goal is to replace the Soyuz MS-22, which last December suffered a coolant leak through a hole in the propulsion unit external radiator (PAO). Soyuz MS-23 was supposed to deliver Oleg Kononenko (Roscosmos), Nikolai Chubb (Roscosmos) and Laurel O’Hara (NASA) to the International Space Station (ISS), which will now take off on September 15 aboard Soyuz MS-23 .24. The initial orbit was 298 by 328 kilometers and the inclination was 51.64 degrees. This is the third orbital launch for Russia in 2023 and the 173rd for the Soyuz spacecraft. It was also the 58th launch of the Soyuz-2.1a rocket.

Soyuz-2.1a rocket with Soyuz MS-23 on its way to the ramp (RKK Energia).

Soyuz MS-23, weighing 7152 kg, carries 429 kg of cargo on board for seven Expedition 68 astronauts, including various experiments (Matrioshka-R, Kardiovektor, Kaskad, Faguen or Probiovit). The Poisk module spacecraft docked on the Russian part of the International Space Station on February 26 at 00:58 UTC and will remain in orbit for 215 days (since it does not carry a crew, the spacecraft will perform the traditional docking scheme in two days instead of a fast docking for three or six hours, as is typical for manned Soyuz spacecraft). Once docked, the upper part of the Soyuz MS-22 crew seats, consisting of Sergey Prokopyev (Roscosmos), Dmitry Petlin (Roscosmos) and Francisco Rubio (NASA), will be moved so that they can use MS-23 as soon as possible in case of an emergency evacuation to the station. Prokopyev, Petelin, and Rubio will return on Soyuz MS-23 on September 27, so they’ll spend 370 days aboard the International Space Station. Thus, the three men would break the record for staying aboard the International Space Station, surpassing the record of 355 days set by Piotr Dubrov and Mark Vande He in 2022 and the record of 340 days and 8 hours set by Scott Kelly and Mikhail Kornienko in 2015. Record 366 days by Vladimir Titov and Musa Manarov in 1988 in Mir, so only the 380 days spent by Sergei Avdeev in 1999 and the 437 days spent by Valery Polyakov in 1995, both in Mir, will be surpassed. For its part, Soyuz MS-22 will return without a crew at the end of March.

Soyuz MS-23 mission logo, without the names of the cosmonauts (Roscosmos).
La Soyuz MS-23 en Baikonur (RKK Energia).
Approach and docking chart in two days (33 orbits) (Roscosmos).

Soyuz MS-23 is the second Soyuz spacecraft to be launched without a crew to the International Space Station after Soyuz MS-14, which in September 2019 traveled without astronauts to test the safety procedures of the Soyuz-2.1a launcher, which from the Soyuz launch finally resolved the MS-16. It replaces Soyuz-FG as the carrier of this manned spacecraft. It is also the second Soyuz craft sent to an unmanned space station to replace another. The first was Soyuz 34 in 1979, which was launched uncrewed to Salyut 6 so that Vladimir Lyagov and Valery Ryumin could return safely after Soyuz 32 had passed its useful life and after Soyuz 33 had failed to dock with the station. On December 15, 2022, Soyuz MS-22 experienced a coolant leak from the PAO thrust unit radiator, which is part of the ship’s SOTR temperature regulation system. As a result, about 34 kg of LZ-TK-2 (ЛЗ-ТК-2), a solution based on the hydrocarbon 2,2,4-trimethylpentane (isooctane), was poured under vacuum. Without a coolant, temperatures inside the Soyuz (SA) capsule cannot be guaranteed to not exceed the maximum temperatures allowed for the crew during the return flight, especially if an emergency situation occurs during return forcing a reentry delay (or if the return occurs after an emergency evacuation to the International Space Station and does not All orbit parameters can be controlled upon return). For this reason, Roscosmos decided to launch Soyuz MS-23 early to replace Soyuz MS-22.

Soyuz MS-22 crew Rubio, Prokopyev and Petelin will return to Soyuz MS-23 after spending more than a year on the International Space Station (Roscosmos).
What should have been the Soyuz MS-23 crew, Laurel O’Hara (NASA), Oleg Kononenko and Nikolai Chupp, will fly on Soyuz MS-24 (NASA).
The crew of Expedition 68 (Soyuz MS-22 and Crew-5) on the International Space Station watching the movie Cheburashka (Roscosmos).
Oleg Kononenko in TsPK training to fly solo Soyuz MS-23 (Roscosmos).

Initially, the possibility of sending the MS-23 with Oleg Kononenko as pilot to ensure a successful docking was considered, but this scenario was finally discarded due to the difficulties involved, as it meant that Rubio would have had to return in the Crew-5 capsule in a configuration with several of doubts regarding safety. However, until MS-23 docks, Roscosmos and NASA have agreed that in the event of an evacuation from the ISS, Rubio will return in Crew-5 with his four companions, yes, without a helmet and with the Soyuz safety seat strapped in, while Prokopyev and Petlin will take their chances. in MS-22. At the same time, the investigation committee set up to clarify the accident came to the conclusion that the hole in the radiator, which had a diameter of only 0.8 mm, was caused by a micrometeorite, which was the same explanation given at the time. The hole that appeared in the orbital module (BO) of Soyuz MS-09 in 2018 (and in which, curiously, Sergey Prokopyev also traveled). To do this, the committee used images taken by the International Space Station’s robot arms, Canadarm 2 from the American part and European ERA from the Russian part. But things took an unexpected turn when, on February 11, the Progress MS-21 cargo ship, which has been docked at the International Space Station since October 28, 2022, experienced another SOTR coolant leak, apparently similar to that experienced by Soyuz MS. -22 (although it appears the coolant on this car was PMS-1.5r, a mixture of hydrocarbons with silicon, rather than LZ-TK-2).

ERA’s European arm inspects Soyuz MS-22 (NASA).
Progress MS-21 docked on the International Space Station (NASA).
MS-21 progresses after separating from the International Space Station (Roscosmos).

The Progress MS-21 leak has set off all the alarms, because the probability that both accidents are related is very high, suggesting that a more plausible cause would be a manufacturing defect rather than a twin accident caused by micrometeorites (no other ship was attached) to the ISS. suffered this kind of problem). For this reason, the Soyuz MS-23 launch was postponed from February 20 to 24, in theory to check the good condition of the new spacecraft’s radiator. Of course, the launch could not be delayed any longer because the Soyuz was already loaded with propellant, a process that required launching it as soon as possible to avoid damaging the tanks and fuel delivery lines (emptying the tanks does not prevent corrosion of the fuel). The Progress MS-21, past its useful life, detached from the International Space Station’s Poisk module on February 18 at 02:26 UTC to leave that port free for Soyuz MS-23. Previously, Progress MS-21 was examined by Canadarm 2 and, during class, by ISS cameras. Soon after, Roscosmos published photos showing a 12-millimeter hole in the radiator of the SOTR of the Progress, although there was no brown spot around it as in the case of the Soyuz MS-22.

Soyuz MS-22 radiator aperture, 0.8 mm (Roscosmos).
Hole in the radiator of the MS-21 Progress (Roscosmos).
The Soyuz SOTR system is divided into three units: BO, SA and PAO (right). In dark blue is the circle of the KNR where the leak occurred (RKK Energia / Roscosmos).
The location of the hole in the Soyuz MS-22 (NASA) radiator.

According to Roscosmos, to no one’s surprise, the Progress hole is also compatible with a micrometeor strike. MS-21 deorbited on February 19 at 03:15 UTC, after spending a day in space. According to Roscosmos, temperatures on the MS-21 did not exceed the operational limits of the vehicle, which confirms the correctness of the decision to use the Soyuz MS-22 in emergency situations. However, it must be remembered that Progress MS-21 is an uncrewed spacecraft; Moreover, it is not clear why a decision was not made to extend the progression journey to test the limits of the SOTR system. Either way, let’s hope refrigerant leaks are a thing of the past and Soyuz MS-23 has an uneventful mission and a normal return to Earth.

Soyuz MS-23 at MIK-KA (254th District) at Baikonur:

Test in an anechoic chamber:

Test in the vacuum chamber:

Solar panel test:

Integration with PkhO clip for trigger linkage:

impulse charge:

Soyuz goods:

Insertion adjustment (GO):

Go to MIK for launcher integration:

Integration with the third phase (Block 1):

Exhaust Tower Integration (SAS):

Integration with the rest of the launcher:

Moving to the ramp:


standoff spacing:

Separation from Soyuz:


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