Astronauts Chen Dong, Chen Zhongrui and Wang Jie attend a see-off ceremony on April 24 for the Shenzhou-20 spaceflight mission at Jiuquan Satellite Launch Center near Jiuquan, Gansu province, China.
A Long March-2F rocket carrying the Shenzhou-20 spacecraft takes off April 24 from the Jiuquan Satellite Launch Center for a crewed mission to China's Tiangong space station.

Three Chinese astronauts have been temporarily stranded in space after the vehicle they were meant to travel aboard back to Earth was hit by space debris.

Just how much damage the vehicle sustained and when – not to mention, how – the astronauts will be able to return to China remains to be seen. An investigation is ongoing, China's human spaceflight agency has announced.

The delay may remind some of the unexpected lengthy stay two NASA astronauts recently experienced when they reached the International Space Station in June 2024 aboard the Boeing Starliner capsule. The situation also highlights the growing threat that increasing amounts of space debris, also called space junk, poses to spacefarers and key orbital infrastructure.

Here's everything to know about the Chinese astronauts stranded at the nation's Tiangong space station.

3 Chinese astronauts stranded at space station after space debris strike

Tiny chunks of space debris are believed to have struck the return vehicle of a Chinese crew of astronauts who were due to head down to Earth following an extended mission in orbit.

China's human spaceflight agency indicated an impact analysis and risk assessment was underway, Reuters reported. The statement from the China Manned Space Agency (CMSA) did not reveal whether the spacecraft was hit by debris mid-flight or while it was docked aboard the Tiangong space station.

Shenzhou-20 mission launched in April

The spacecraft in question was the Shenzhou-20 capsule, which in April transported a crew of three astronauts to the space station – Chen Dong, Chen Zhongrui and Wang Jie.

The mission is part of China's Shenzhou program, which takes trios of Chinese astronauts to and from Tiangong for six-month stays, where they perform a variety of tasks.

The mission's replacements, part of the Shenzhou-21 mission, docked with the station Saturday, Nov. 1. The crews of both vessels were in the midst of a handover period as the new arrivals spent a few days familiarizing themselves with the outpost before the Shenzhou-20 were to depart Wednesday, Nov. 5.

While weather conditions have previously delayed return missions for previous Shenzhou crews, this is the first time that a return mission has been delayed by space debris, Reuters reported.

How will the Chinese astronauts return to Earth?

China has not announced a new plan for the astronauts' return journey.

But existing protocols would establish Shenzhou-21 as the return vessel if Shenzhou-20 cannot be repaired aboard Tiangong, Reuters reported. A backup Shenzhou spacecraft would be sent from the Jiuquan Satellite Launch Centre in northwest China in the event of an orbital emergency.

What is Tiangong? What to know about China's space station

Because China is not among the partners on the International Space Station, the nation operates its own outpost in orbit.

Named Tiangong, the three module space station became fully operational in 2022 in low-Earth orbit, according to the nonprofit Planetary Society.

China plans to expand Tiangong in the coming years by adding more modules, along with plans to launch a space telescope similar to NASA's Hubble that will orbit nearby and be able to dock for repairs.

Delay resembles Boeing Starliner debacle at International Space Station

The predicament of the Chinese astronauts resembles, to an extent, the extended stay two NASA astronauts endured between June 2024 and March 2025 at the International Space Station after crewing the infamous Boeing Starliner capsule.

The circumstances, though, that left Butch Wilmore and Suni Williams at the rival orbital outpost were much different. Rather than rogue space junk, it was unexpected technical issues with the astronauts' Starliner spacecraft that left them without a vehicle for a return journey.

Williams and Wilmore – the latter of whom has since retired – were ultimately at the space station for 286 days before returning with a SpaceX mission known as Crew-9 on a Dragon capsule. NASA astronaut Frank Rubio also found himself in space for much longer than he planned – an American record of 371 days between 2022-23 – when a Russian Soyuz he took to the station encountered issues, and a replacement had to be sent up.

How much of an orbital threat does space junk pose?

Space junk composed primarily of retired satellites and other human-made objects, like used rocket boosters, are a growing problem littering Earth's orbit. Left unchecked, the junkyard of orbital debris can pose dangers to both crewed and uncrewed space missions, as well as astronauts in orbit.

In November 2024, for instance, the International Space Station found itself in the way of a hunk of space junk.

A Russian cargo ship docked at the space station fired its thrusters for more than five minutes to "provide an extra margin of distance" for the hunk of debris, NASA said. While the inbound object, which was debris from a defunct meteorological satellite, was not necessarily on a collision course with the station, NASA said the evasive maneuver provided a little more cushion for it to safely whizz by.

For that reason, calls have been growing for increased international cooperation to address the growing danger floating hundreds of miles above Earth.

At a forum last year, for instance, Chinese President Xi Jinping called on Chinese and Arab countries to jointly build a "space debris observation center."

Contributing: Reuters

Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@gannett.com

This article originally appeared on USA TODAY: Rogue space junk strands 3 Chinese astronauts at Tiangong space station. What we know

Reporting by Eric Lagatta, USA TODAY / USA TODAY

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