November 7, 2025
4 minute read
Stranded Chinese astronauts demonstrate the dangers of space debris
Three Chinese astronauts are likely to return safely to Earth after a reported collision with space debris. But the incident highlights the growing risk of orbital debris.
Wang Jie, Chen Dong and Chen Zhongrui before the April 2025 launch on the Shenzhou 20 spacecraft.
This week, the China Manned Space Agency (CMSA) announced that the homecoming of three of its astronauts had been delayed due to space debris hit Shenzhou 20 spacecraft that would take them back to Earth from the Chinese Tiangong space station. While the agency continues to investigate the extent of the damage, independent experts say the incident is a clear sign that the danger of orbital debris will only increase.
Although this is the first known case of a return to Earth being affected by debris, scientists have long warned that the growing amount of space debris makes such disruptions inevitable.
“It was just a matter of time,” says research analyst Lauren Kahn of Georgetown University.
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Space debris is essentially all man-made objects floating in space that are no longer useful. As the number of orbital launches and other space activities has increased, so has the number of fragments created by collisions, accidental decays, spent rocket stages, and more. In Earth orbit, debris can drift through space for decades, gradually sinking due to atmospheric drag, before finally experiencing a fiery re-entry. As a result, Kahn said, some parts of Earth's orbital environment are rife with hazardous objects that could collide with vital space infrastructure.
A recent analysisco-authored with Kahn, tracked 34,000 pieces of space debris larger than 10 centimeters that were cataloged from 1958 to mid-April 2025. The researchers found that 73 percent of all tracked debris in orbit today can be attributed to just 20 major sources—from launches in China, the United States and Russia.
According to NASAToday there are more than 45,000 artificial objects in Earth's orbit. Some could cause serious damage to space stations and satellites, threatening the global space economy hovering above us, currently valued at more than $600 billion.
While objects larger than 10 cm can be detected and tracked, the real danger comes from the more difficult to see debris, which can be the size of a bullet and travel at speeds of more than 27,000 kilometers per hour. “These are the scariest ones,” says Jonathan McDowell, an astronomer at the Center for Astrophysics | Harvard and Smithsonian Institution. “They're time bombs in orbit.”
Although the CMSA did not disclose more details about the object that may have fallen into Shenzhou 20 spacecraft, McDowell says even a small piece could be dangerous if it hits a key system.
However, McDowell said the astronauts are expected to be safe because China has another spacecraft docked at the space station ready to pick them up if they are unable to return to Earth. Shenzhou 20 craft.
Cascade of collisions
The biggest fear among space scientists is that the debris could set off a chain reaction of satellite collisions, creating even more debris – a nightmare scenario known as Kessler syndrome.
In recent years, astronomers tracking space debris have focused their attention on low-Earth orbit (LEO), where human space missions operate alongside communications and observation satellites. The majority of space debris—more than 83 percent of tracked objects as of April 2025—is in Earth orbit, according to an analysis co-authored by Kahn.
There are now about 13,000 active satellites in Earth's orbit, which is about 10 times more than ten years ago. Because of this, McDowell says, satellites often have to move out of the way to avoid colliding with other satellites or debris. These movements, called evasive maneuvers, already occur tens of thousands of times every year. The number of maneuvers is growing much faster than the number of satellites, because more satellites mean more chances to cross paths. If the number of satellites increases by a factor of 10, the number of maneuvers could increase by a factor of 100, making it much more difficult to safely manage orbital motion.
Even as that risk grows rapidly, there are still plans to launch megaconstellations of tiny satellites like those already in orbit as part of SpaceX's Starlink system, as well as recent momentum for orbital data centers such as Nvidia's Starcloud. “Right now there is no limit to the number of satellites you can launch,” McDowell says.
Two issues are particularly troubling, says Victoria Samson, chief director of space security and stability at the Colorado-based nonprofit Secure World Foundation: There is currently no way to clean up space debris, and there is very little international coordination to prevent further debris-generating collisions, especially between the United States and China.
This is not the first time China's human spaceflight program has encountered dangerous debris. In March 2024, CMSA said in a statement that a fragment hit one of the Tiangong space station's solar panels, damaging it and causing a loss of power, forcing astronauts to spacewalk for repairs.
But the potential damage caused by the growing number of collisions cannot always be repaired during spacewalks. In addition to the risk to space infrastructure, the growing number of astronauts in orbit is a major concern. “There are a lot of people there,” Samson says.
