1. The Coolant Leak Found on the Soyuz MS-22 in December 2022
On December 15, 2022, coolant began leaking from the Soyuz MS-22, which was docked at the ISS. On December 19, the external radiator was inspected using the Canadarm2 robotic arm, and a hole approximately 0.8 mm in size was discovered [8]. Roscosmos initially suspected that a micrometeorite had struck the ship. This was a working theory during the investigation; early reports also mentioned the possibility of space debris [8]. The Soyuz serves as the return vehicle for crew members staying at the ISS. The question arose: was it safe to send people home in a ship with a hole in its cooling system? Attention focused on the next decision.
2. Why the Soyuz MS-22 Was Sent Back to Earth Empty
On January 11, 2023, NASA and Roscosmos announced that MS-22 would not be used for the crew’s return. It was reported that the reason was that repairing the thermal control system was complex, costly, and not wise [9]. Instead, an empty Soyuz MS-23 was launched a few days later than originally planned. The launch date was February 24 in local Russian time, or February 23 in US Eastern Time [10]. The three crew members—Prokopyev, Petelin, and Rubio—returned to Earth in MS-23 [9], while MS-22 returned unmanned on March 28 [11]. They did not ride home in the damaged ship. The problem was solved by sending an unmanned rescue ship to them.
3. The Three Parts of the Soyuz Spacecraft
The Soyuz is built in three main parts: the orbital module, which docks with the ISS; the descent module, where the crew sits during launch and return; and the service module, which holds equipment and propulsion [2]. The capacity is said to be 2 to 3 people. When returning to Earth, the three parts separate before entering the atmosphere. Only the descent module, which has a heat shield, lands on the surface [2]. It is like leaving large luggage in a station locker and taking only a small bag home. However, unlike luggage, the separated parts do not return to Earth, and you cannot go back for them. Separating the ship allows for different designs for space operations and Earth return. Note that this explanation of the benefits is an interpretation for this article, not a direct quote from JAXA materials.
Note: During return, the three parts separate before entering the atmosphere, and only the descent module with its heat shield returns to Earth [2].
4. How Two Soyuz Accidents Changed the Design
In April 1967, Soyuz 1, the first crewed flight, failed to deploy its parachute during return. Cosmonaut Komarov died. After this, the design was significantly reviewed. Details of the cause are not covered here [4]. On June 29, 1971, during Soyuz 11, a ventilation valve opened when the modules separated. Air was lost from the cabin during descent, and three people died [5]. Afterward, the crew was reduced to two people, and the design was changed so that they wore Sokol spacesuits during launch and landing. This created room to put on the suits [5]. The history of this ship shows that it was fixed after accidents, rather than just being an old design.
5. How the Soyuz Escape System Saved Crews in Two Launch Emergencies
The Soyuz has an escape system that pulls the crew module away from the rocket if a problem occurs during launch. In 1983, a rocket fire and explosion happened on the launch pad, but the escape system saved the crew [4]. On October 11, 2018, during the launch of MS-10, a problem occurred with booster separation. The escape system activated automatically. The two crew members, Ovchinin and Hague, landed about 19 minutes and 41 seconds after launch. They endured a maximum deceleration of about 6.7G and were in good condition [6]. This accident was a rocket problem, not a failure of the spacecraft itself. Crewed flights resumed on December 3, less than two months later [6].
6. Why the Soyuz Has Been Improved in Small Steps
The Soyuz has evolved through several main versions: the original (1967), TMA (first flight 2002), TMA-M (2010–2016), and MS (2016–). Dates vary by a few years depending on whether they refer to the first flight or the operational period [2]. JAXA explains that Russia has maintained safety and reliability by making small improvements without changing the basic design [3]. In the TMA-M, analog controls became digital, and old computers were replaced. In the MS, communication equipment was updated, and the range of communication with the ground expanded using data relay satellites [3]. A 2009 article stated that the basic design has not changed since the 1960s. It quoted JAXA Professor Emeritus Yasunori Matogawa, who said they have repeated the process of "improving what is bad" [7]. The MS is said to be the last improvement for the current Soyuz. This is reported information, and what happened afterward is not written in the materials.
Note: Russia states that it has ensured safety and reliability by making small improvements without changing the basic design [3].
7. How the Soyuz Went from Only Crew Transport to Emergency Shelter on the ISS
From the retirement of the Space Shuttle in 2011 until the launch of SpaceX’s Crew Dragon in 2020, the Soyuz was the only crewed transport to the ISS [4]. This "only" status applied specifically to that period. At the ISS, crew members sometimes shelter in the docked Soyuz if there is a warning about approaching debris. An example from March 2012 was covered in another note. The Soyuz is a return vehicle, but it also serves as an emergency shelter.
8. Activity: Comparing the Soyuz Versions and Their Dates
Open the JAXA Soyuz page [2] and compare the names of the versions, such as TMA, TMA-M, and MS, with the dates listed. Mark the parts you think changed significantly and the parts that stayed the same. Write in your notebook whether this matches JAXA’s explanation of "making small improvements" [3]. Note that dates for some versions vary by a few years depending on the source. Marking which counting method is used will help you avoid confusion when reviewing your notes later.