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Source: Global Times

[Global Times Special Correspondent Chen Yang] After more than two months of repeated struggles, the two American astronauts stranded at the International Space Station due to a malfunction of the Boeing "Starliner" spacecraft finally waited for "interstellar rescue" - the manned "Dragon" spacecraft of the US Space Exploration Technology Company (SpaceX) will take them back to Earth in February next year, and the "Starliner" spacecraft will return to Earth in unmanned mode in September this year. But behind this difficult decision made by the National Aeronautics and Space Administration (NASA) is full of helplessness and uncertainty.

No other solution

According to CNN on the 25th, NASA Administrator Bill Nelson said that the decision to let the Boeing spacecraft return to Earth empty was "out of a commitment to safety." This will allow the collection of relevant test data to continue during the return of the spacecraft, while preventing the astronauts from "taking unnecessary risks." On June 5 this year, American astronauts Wilmore and Williams boarded the "Starliner" on the first manned flight mission to the International Space Station. They were originally scheduled to carry out an 8-day test flight mission, but due to problems such as thruster failure and helium leakage in the spacecraft, the return time has been repeatedly postponed. So far, they have been stranded in the space station for more than two months.

According to the US "Space" website, NASA's final decision to let the "Starliner" spacecraft return empty is related to several factors. The first is the need to vacate the docking port of the International Space Station so that a new batch of astronauts (Crew-9) can board the "Freedom" manned "Dragon" spacecraft to enter the International Space Station. At present, the astronaut handover of the International Space Station adopts the method of on-orbit rotation, that is, the new batch of astronauts arrive at the International Space Station to complete the work handover before the previous batch of astronauts leave, which means that the International Space Station will dock two manned spacecraft at the same time. At present, the two docking ports of the International Space Station that can dock the US standard manned spacecraft are respectively docked with the "Endeavour" manned "Dragon" spacecraft and the "Starliner" spacecraft carrying the previous batch of astronauts (Crew-8). This also means that the "Starliner" must first leave the International Space Station to vacate the docking port before the new manned "Dragon" spacecraft can be launched.

Secondly, according to NASA's plan, Wilmore and Williams were forced to stay in space for several more months, which was also a helpless choice - the Endeavour manned Dragon spacecraft currently docked with the International Space Station is fully occupied. When SpaceX first developed the manned Dragon spacecraft, the design indicator was that it could carry 7 astronauts at the same time, but after evaluation, NASA believed that there was a problem with the tilt angle of its internal seats, which might cause serious impact to the astronauts when the spacecraft landed. After improvements, the tilt angle of the manned Dragon spacecraft's seats was flattened, but this also reduced the number of people on board to 4.

In addition, according to the relevant regulations of NASA and SpaceX, astronauts must wear the matching cabin spacesuits when boarding the manned Dragon spacecraft. At present, there are no extra SpaceX cabin spacesuits on the International Space Station. Wilmore and Williams need to wait for the Freedom Dragon spacecraft to arrive at the International Space Station and bring their spacesuits up together before they can transfer to the manned Dragon spacecraft to return. Therefore, the earlier optimistic prediction that the two astronauts could board the Endeavour Dragon spacecraft and return with the four astronauts of the Crew-8 mission group is actually not feasible.

However, when asked whether there are any other solutions for the two American astronauts to return to Earth besides the manned Dragon spacecraft, SpaceX CEO Musk said on social media: "Russia is the only option." Currently, the International Space Station has several Russian-standard docking ports that can dock with the Russian Soyuz manned spacecraft, but the outside world generally believes that given the current almost frozen US-Russia relations, the United States is unlikely to ask Russia for help on this issue unless it has to.

The return journey is full of unknowns

The return journey of the Starliner spacecraft is not very optimistic. NASA and Boeing have been arguing for quite a long time about whether a series of failures encountered by the spacecraft have been resolved.

Long before the launch, Boeing engineers confirmed that the "Starliner" spacecraft had a helium valve leak; on the way to the International Space Station, 5 of the spacecraft's 28 attitude control thrusters also failed. While docked at the International Space Station, Boeing repeatedly tested the spacecraft in an attempt to find the fault point. Mark Nappi, Boeing's vice president and manager of the commercial manned space program, said that engineers are dealing with "more than 30 measures" related to thruster problems and helium leaks, but have not come up with a convincing conclusion for NASA. The Boeing engineering team believes that the reason for the failure of the attitude control thrusters is that the design defects of the spacecraft caused the attitude control thrusters to be concentrated in four doghouse-shaped thruster compartments around the spacecraft service module. The heat released when the thrusters were started could not be discharged immediately, which caused the thrusters to automatically shut down due to overheating. However, Boeing later admitted that it failed to fully reproduce the problems of the "Starliner" spacecraft attitude control thrusters in space during ground tests at the White Sands Proving Ground in New Mexico, so NASA was skeptical about the actual effectiveness of these improvement measures.

According to the "Space" website, Boeing said that the "Starliner" spacecraft carries 10 times the amount of helium in stock, so a small leak will not cause safety problems. However, NASA is very worried about the failure of the spacecraft's attitude control thrusters, which has not been resolved. These thrusters are mainly used to accurately adjust the position of the spacecraft. If they fail again during the phase of leaving the International Space Station, the spacecraft cannot guarantee safe departure from the International Space Station, and there is even a risk of collision. If a failure occurs during reentry, the spacecraft may enter the atmosphere at a wrong angle and at high speed, causing the spacecraft to burn up in the high temperature generated by friction with the air.

Worse still, although the Starliner spacecraft had already autonomously completed the entire process of docking, detaching and returning to Earth with the International Space Station in the second unmanned test, it currently does not have the ability to autonomously detach from the International Space Station and return to Earth due to a subsequent change in the flight control software. Boeing has promised to complete the software update for the unmanned return mission of the spacecraft in early September. Prior to this, the spacecraft cannot be moved unless the astronauts operate it personally.

Boeing's space journey is difficult

CNN stated that because NASA and Boeing signed a fixed contract, Boeing must bear all losses caused by delays in the development of the spacecraft. Boeing has already lost $1.5 billion on the project. Even if the "Starliner" spacecraft can successfully land autonomously in the scheduled landing area in the future, its first manned flight mission obviously did not pass the test. This mission has caused Boeing to suffer a huge reputational impact. Boeing must completely solve the helium leak and thruster problems before the next flight of the "Starliner" spacecraft. If Boeing wants to continue to fulfill its contract to transport astronauts to the International Space Station, it must obtain relevant certification from NASA. After this incomplete test flight, Boeing will most likely need to prepare for a second manned flight test at its own expense.

Despite speculation that Boeing may decide to "cut its losses" and abandon the development of the Starliner spacecraft in the future, NASA has expressed its support for Boeing. At the press conference, Nelson expressed his confidence in the future of the Starliner spacecraft, saying he believes the spacecraft will be ready to carry astronauts again.

Some analysts believe that NASA has always emphasized that "don't put all your eggs in one basket" and is worried that SpaceX, which will become the "dominant company" in the future, may in turn affect the United States' space capabilities.

Due to competition from SpaceX in the space launch market, the United Launch Alliance, a joint venture between Boeing and Lockheed Martin, has been in a slump. This space launch giant, which once monopolized the U.S. government's space launch missions, has lost large orders and is now facing the situation of being sold.