Possible Space Debris Strike Delays Return of Chinese Astronauts From Space Station

China’s human spaceflight agency has delayed the return of the Shenzhou-20 spacecraft and its crew from the country’s space station, Tiangong, after a possible debris impact. It is not yet clear when the three astronauts will return to Earth.

“The Shenzhou 20 crewed spacecraft is suspected of being struck by a small piece of space debris, and impact analysis and risk assessment are underway,†the China Manned Space Engineering Office (CMSEO) said in a statement on Wednesday.

“To ensure the safety and health of the astronauts and the complete success of the mission, it has been decided that the Shenzhou 20 return mission, originally scheduled for Nov. 5, will be postponed.â€

The CMSEO did not provide details about the timing, location, or nature of the strike. It’s possible the object that hit the spacecraft was a small, rogue chunk of space tech, but it may have also been a micrometeorite. If it was the former, the incident would highlight a growing threat to human spaceflight as low-Earth orbit becomes increasingly congested with space junk.

A sudden change of plans

Shenzhou 20 launched from Jiuquan Satellite Launch Center in northern China’s Gobi Desert on April 24, carrying commander Chen Dong and crewmates Chen Zhongrui and Wang Jie to the Tiangong space station.

Their replacements—the three astronauts of the Shenzhou 21 mission—arrived at the space station on October 31 to begin their six-month rotation. Now, both crews will remain aboard Tiangong while authorities conduct an impact analysis of the Shenzhou 20 spacecraft.

There was no sign of any issues in the days leading up to Shenzhou’s scheduled departure. On Tuesday, Chinese state media reported that the two crews enjoyed a meal of baked chicken cooked in an oven delivered by the Shenzhou 21 astronauts. They also reportedly completed a handover ceremony, signaling the formal transfer of responsibility for space station operations.

Hurry up and wait

Objects in low-Earth orbit travel about 5 miles per second (8 kilometers per second), though the relative velocities of two objects vary. That means even a tiny piece of space debris can cause significant damage, potentially compromising hardware or systems that are critical for a safe reentry into Earth’s atmosphere.

Two primary concerns are potential damage to the spacecraft’s heat shield or its parachute deployment hardware. The Shenzhou 20 spacecraft will likely undergo telemetry and leak tests, measures to verify its guidance and propulsion systems, and screening for impacts in accelerometer and acoustic sensor data, according to SpaceNews.

It’s unclear how long this process will take. If CMSEO determines that Shenzhou 20 is unfit to fly its crew home and cannot be repaired aboard Tiangong, Shenzhou 21 will be used to transport the three astronauts back to Earth, Reuters reports.

If both spacecraft are damaged beyond repair, a backup Shenzhou could launch from Jiuquan Satellite Launch Center to retrieve the astronauts. A spare Long March-2F rocket and Shenzhou spacecraft are always on standby at the launch center in case of emergency, according to Reuters.

This isn’t the first time astronauts have been forced to extend their orbital missions (looking at you, Boeing), but it is the first such incident to result from a suspected space debris impact, SpaceNews reports. This is a growing concern as humanity launches more and more spacecraft, spurring experts to call for better quantification and mitigation of space junk in low-Earth orbit.