This article is jointly presented by the Toutiao Top Picks project. Unauthorized reproduction is prohibited.

At 16:40 Beijing Time on November 14, 2025, the return capsule of Shenzhou 21 successfully landed at the Dongfeng Landing Site. Subsequently, the astronauts Chen Dong, Chen Zhongrui, and Wang Jie of Shenzhou 20 safely exited the spacecraft and stepped onto their long-lost home, Earth.

With this, the space journey of the Shenzhou 20 crew has been successfully completed. Chen Dong became the first Chinese astronaut to stay in orbit for more than 400 days, and he is also currently the Chinese astronaut who has performed the most extravehicular activities (EVAs). The first flight of Chen Zhongrui and Wang Jie was successfully completed.

Earlier, the China Manned Space Engineering Office confirmed that the return capsule of Shenzhou 20 had a small crack on its window glass, which, after comprehensive evaluation, did not meet the safety conditions for manned return. This unexpected situation undoubtedly brought unprecedented challenges to this mission.

After careful assessment through multiple methods such as photo interpretation, design review, and simulation analysis, the initial judgment was that the window crack was most likely caused by an external impact from space debris. Faced with this "uninvited guest" in space, China adhered to the principle of putting life first and safety first, and made a decisive decision: the Shenzhou 20 spacecraft would temporarily not execute the return mission and instead remain in orbit for scientific experiments. This calm and responsible decision marked the first time China initiated the "crew exchange return" mechanism due to suspected damage to a manned spacecraft in orbit, paving an absolutely safe path home for the crew.

Chen Lan, a contributor to Observer Network and a space enthusiast, pointed out that although space debris impacts have occurred multiple times in aerospace history, China's unique "rolling backup" contingency plan enabled a rapid response and no one being stranded in space, demonstrating outstanding emergency capabilities. This decision stemmed from a cautious risk assessment of extremely low risk, and the Shenzhou 20 remaining in orbit turned an unexpected challenge into a rare research opportunity.

Photo of the safe exit of astronauts Chen Dong, Chen Zhongrui, and Wang Jie

On November 14 at 11:14, the Shenzhou 21 manned spacecraft successfully separated from the space station complex IC photo

Space collision is not the first case, "China's response is much faster"

The Shenzhou 20 spacecraft, originally scheduled to return to Earth on November 5, encountered an unexpected incident shortly before its return. On that day, the China Manned Space Engineering Office announced that the Shenzhou 20 manned spacecraft had potentially been hit by micro-space debris during the return preparation phase and was urgently conducting impact analysis and risk assessment. To maximize the safety of the astronauts and the success of the mission, the return mission was urgently postponed. This was the first time in the history of China's manned space program that a return plan was adjusted due to the risk of space debris.

Just before the accident, on November 4, a "key handover" was held inside the Tiangong space station. The Shenzhou 20 and Shenzhou 21 crews completed their work handover, symbolically transferring control of the space station in orbit, which had already marked the end of this six-month mission.

Collisions with space debris and micrometeoroids are long-term challenges in manned spaceflight. This hidden threat in space once again came into public view. Chen Lan cited an example: On December 15, 2022, the Russian Soyuz MS-22 spacecraft was hit by a micrometeoroid, causing depressurization and coolant leakage. Because the damaged spacecraft could not return safely, the crew remained in the space station. Russia launched an unmanned Soyuz MS-23 spacecraft on February 24 of the following year, and the crew returned to Earth on September 27, extending the space station mission from six months to a full year.

On December 15, 2022, the Russian Soyuz MS-22 spacecraft was hit by a micrometeoroid, causing depressurization and coolant leakage NASA

Chen Lan said that this accident was similar to our situation, but our response time was much faster because Shenzhou 20 was always ready. Progress 21 also experienced a similar situation, but it was uncrewed and didn't need to return, so it didn't attract attention.

Crew vehicle window glass collisions have also occurred. For example, in May 2016, a 7 mm diameter pit was found on a window of the International Space Station's Cupola module. Fortunately, the multi-layer glass was thick enough to prevent serious consequences. In the history of many space shuttle flights, window glass was also hit and formed similar small pits, but none caused any problems.

Photo of the International Space Station's Cupola module window glass being hit in May 2016

Chen Lan pointed out that window collisions can be visually observed, but collisions on other parts of the spacecraft are difficult to detect, usually only discovered when a depressurization or other failure occurs. He used the Russian MS-22 incident as an example, saying that the leaked coolant resembled "snowflakes" in space, and finding a millimeter-sized impact point, even with a robotic arm, is extremely difficult.

He further explained that the space station is equipped with complete sensors and alarm systems, which can monitor abnormal situations like depressurization in a timely manner. If the worst-case scenario occurs, astronauts can initiate isolation procedures and close the damaged compartment. As in the case of the Mir space station, it continued to operate for several years after isolating the pressurized compartment.

"Stay in orbit" has special value: turning challenges into opportunities

According to the introduction, the assessment of the severity of the impact requires cooperation between the space station and the ground. In cases of insufficient information, conservative decisions are often made.

Improving the protective capabilities of spacecraft (such as enhancing the impact resistance of window glass, space station micrometeoroid protection shields, etc.), complete monitoring and alarm systems, and complete emergency measures and contingency plans are generally the measures to deal with micrometeoroids and space debris. Chen Lan pointed out that China's practice of having a standby spacecraft is currently unique in the world, and this time it proved invaluable. Historically, only later flights of some space shuttles adopted this approach.

However, according to Chen Lan, the decision for the Shenzhou 20 crew to return on the Shenzhou 21 was "unexpected." He initially thought that the Shenzhou 22 would be launched first and approach the space station, then the Shenzhou 20 would detach, the Shenzhou 22 would dock, and finally the astronauts would return on the Shenzhou 21.

According to the rules of the International Space Station, if there are people onboard, two spacecraft (for rescue purposes) must be docked to ensure that all crew members can return at any time. Otherwise, if the space station itself or the astronauts' bodies encounter emergencies, it would be very troublesome.

"Therefore, my guess is that the risk caused by the Shenzhou 20 window being hit should be very small. Even if the Shenzhou 21 crew encounters an emergency, they can return on the slightly damaged Shenzhou 20, and the probability of a problem is very low (even if it does not meet the hard requirements for release). Moreover, the Shenzhou 22 is about to be launched, which can reduce the risk to the lowest possible level."

Chen Lan emphasized that although the Shenzhou 20 can no longer complete the return mission, continuing to remain in orbit also has special value. First, small probability events such as window impacts are rare and provide a good opportunity for long-term observation of crack changes, which helps further improve window design. Additionally, long-term docking of two spacecraft before the arrival of the Shenzhou 23 not only increases additional space, but also has reference value for the operation of the space station under future six-person permanent mode.

Shenzhou 20 and Shenzhou 21 handed over the keys to the space station CCTV News

Seemingly unexpected, the decision actually reflects the composure and wisdom of a mature aerospace system. Facing the uncertainties of space exploration, China's aerospace has proven its systematic safety assurance capabilities and innovative thinking of turning challenges into opportunities through a perfect emergency practice!

Original article: https://www.toutiao.com/article/7572548401665966628/

Statement: The article represents the views of the author. Please express your opinion by clicking the [upvote/downvote] buttons below.