After a brief delay caused by space debris impacting their craft, three Chinese astronauts are set to return to Earth on Friday, according to the China Manned Space Agency (CMSA). The astronauts have transferred to a different spacecraft for their journey back.

For the first time, the Chinese space agency disclosed the extent of the damage caused by the debris, noting that “tiny cracks” appeared in a small window of the Shenzhou-20 spacecraft’s return capsule.

The agency emphasized that the capsule does not adhere to the safety standards necessary for a crewed return. Consequently, Shenzhou-20 will remain in orbit to carry out further experiments, as detailed in their official statement.

Initially, the astronauts were scheduled to return nine days earlier, following a six-month mission aboard China’s Tiangong space station. This mission is part of the country’s Shenzhou program, also known as “Divine Vessel.” The delay occurred when the crack was identified.

The crew has now departed Tiangong and is en route to Earth on the Shenzhou-21 spacecraft. They are expected to land at the Dongfeng site in China’s Inner Mongolia Autonomous Region on Friday afternoon, as confirmed by the CMSA.

The mission began in April and went smoothly until, the CMSA said, a “suspected impact from tiny space debris” forced a postponement of the Shenzhou-20’s return, originally scheduled for November 5.

The delay, while only nine days, is highly unusual for a program that has run like clockwork and in the past year reached new milestones, with the deployment of astronauts born in the 1990s, a world-record spacewalk and plans to send the first foreign astronaut, from Pakistan, to Tiangong next year.

Every Shenzhou mission aboard Tiangong ends with a handover, where the departing crew welcomes the arriving crew that will take over the space station’s operations.

During the handover period of several days, two Shenzhou vessels are docked at the space station.

China’s manned space program now has to deal with another logistical headache – how to get the space station’s newly arrived crew home in the event of an emergency.

CMSA said the Shenzhou-22 spacecraft would be launched at “an appropriate time in the future.”

SPACE JUNK DANGER

The damage to the Chinese spacecraft highlights the challenges posed by growing quantities of “space junk” to space exploration.

“Due to the sharp increase in orbital debris, the likelihood of damage to spacecraft and space stations of all countries has risen significantly,” Igor Marinin, a member of the Russian Academy of Cosmonautics in Moscow, told Reuters.

While this is the first known debris disruption for a Shenzhou mission, junk in space has ensnared past missions to the International Space Station, the 25-year-old science lab led by the United States and Russia.

The SpaceX capsule NASA uses to transport astronauts to the ISS has had to dodge suspected pieces of space debris during flight, while the football field-sized station itself has maneuvered several times to steer clear of junk.

Breakups of old, defunct satellites, mishaps with active ones and anti-satellite weapon tests can create vast swarms of space debris that remain in orbit for years.

The sudden breakup of an old Russian satellite last year created at least 180 pieces of trackable debris, forcing ISS astronauts to prepare for evacuation. A spent Chinese rocket stage later that year created nearly 1,000 pieces of junk after possibly colliding with debris.

The threat has prompted calls for rival space powers US and China to collaborate on space debris mitigation and satellite traffic rules, though US law largely bars NASA from working with Beijing’s space program.

Still, the US and China have increasingly coordinated on space safety matters in recent years, largely on an ad-hoc basis. Chinese spacecraft maneuver alerts to U.S. operators stepped up last year to the Pentagon and with NASA, Reuters reported.

US space agency NASA last year saw two of their astronauts getting stranded for nine months in the ISS due to propulsion system issues in their vessel, a Boeing Starliner spacecraft.