Space junk may have struck a Chinese crew ship in low-Earth orbit

What we know

The Shenzhou 20 astronauts arrived at the Tiangong station in April. Their replacements on the Shenzhou 21 mission docked with Tiangong on Friday, temporarily raising the station’s crew size to six people. After several days of joint operations, the six astronauts held a handover ceremony early Tuesday to formally transfer command of the outpost to the new crew.

Less than 24 hours later, Chinese officials decided to call off Shenzhou 20’s departure from Tiangong. The statement from the China Manned Space Agency did not say what part of the Shenzhou 20 spacecraft may have been damaged, what evidence led engineers to suspect space debris was the culprit, or how long Shenzhou 20’s departure might be postponed.

This view shows a Shenzhou spacecraft departing the Tiangong space station in 2023. Credit: China Manned Space Agency

The ship has three sections, with a landing capsule positioned between the crew living quarters and a power and propulsion module. The modules separate from one another before reentry, and the return craft heads for a parachute-assisted landing while the other elements burn up during atmospheric reentry.

The Shenzhou 20 crew is led by commander Chen Dong, a veteran astronaut and former Chinese fighter pilot on his third trip to space. Two spaceflight rookies, Chen Zhongrui and Wang Jie, are also awaiting their homecoming after six months in orbit.

It’s rare for China to disclose a problem during an ongoing space mission. Operations on China’s Tiangong space station have proceeded without significant issues since crews started visiting the complex in 2021, but Chinese officials were aware of the risk of space junk. The Shenzhou 20 astronauts ventured outside Tiangong on four spacewalks during their mission. All of the excursions focused on beefing up external shielding to protect the station from space debris strikes, according to China’s official accounts of the spacewalks.

The station suffered a partial power loss after a piece of space junk hit one of its solar panels in 2023, prompting repairs on several spacewalks last year. That was followed by a spacewalking frenzy to install what Chinese state media called “space debris protection devices” on the outside of the complex.

China’s Tiangong space station orbits nearly 240 miles (380 kilometers) above Earth, as seen in this image taken from a visiting Shenzhou spacecraft in 2023. Credit: China Manned Space Agency

The International Space Station, led by the United States and Russia, has also had run-ins with small fragments of space debris. One such event happened in 2021, when a piece of space junk just 1 millimeter in size—too small to be tracked from the ground—punched a hole in the space station’s Canadian-built robotic arm. The impact didn’t affect the performance of the robotic arm, but an object that small traveling at nearly 5 miles per second could do damage if it hit a more sensitive area.

There was no immediate indication from China that engineers might deem the Shenzhou 20 spacecraft unsafe for reentry and landing. If the ship is damaged beyond repair, officials have a backup Shenzhou spacecraft and rocket that could launch on a rescue mission from the country’s space center in Jiuquan, an isolated base in the Gobi Desert of northwestern China.