So much junk is filling Earth’s orbit that collision avoidance has become a busy business.

“We’re talking about the dead satellites, the rocket bodies, the fairings, the wrenches, the gloves, and things like that that have been left up in orbit,” physicist Thomas Berger said in a press briefing at the fall meeting of the American Geophysical Union in Washington DC on December 11.

Along with those recognizable objects, there are millions of bits of debris in orbit traveling faster than a bullet.

All that stuff is building up and increasing the risk of explosive space collisions, which is dangerous for astronauts and satellites.

A space-debris hit to space shuttle Endeavour’s radiator, found after one of its missions. NASA

Earth’s orbit is so crowded with junk now that roughly 1,000 warnings about possible impending collisions go out to satellite operators each day, Berger said.

For example, Araz Feyzi, a co-founder of the orbital data company Kayhan Space, told BI in an email that some of its customer satellites get up to 800 alerts per day from the US Space Force.

Siamak Hesar, the company’s other co-founder, later wrote in a SpaceNews editorial that the company tracks “more than 60,000 alerts per week for a constellation of around 100 satellites.”

Most of those warnings come from one neighborhood of Earth’s orbit, around 550 kilometers (340 miles) in altitude, where SpaceX’s Starlink satellites live.

“It’s getting difficult for satellite operators to determine which of these warnings is important and which they have to pay attention to,” said Berger, who is the executive director of the Space Weather Technology, Research and Education Center at the University of Colorado, Boulder.

Because trackers can’t perfectly predict objects’ positions in space, these collision warnings are triggered when objects are expected to pass each other at a close distance. Only a small fraction of warnings actually end in a collision.

When space objects do collide, they eject high-speed debris in multiple directions, creating a new zone of hazardous junk in orbit.

A projectile strikes a mock-up of a spacecraft in a NASA-Air Force test meant to simulate space debris collisions. Arnold Engineering Development Complex/Air Force

“It could generate a chain reaction, an unstoppable chain reaction of further collisions, ultimately resulting in a completely filled-up space environment,” Berger said.

In the worst-case scenario, orbit could become so crowded that there’s no safe space for new rocket launches.

That’s a situation experts call Kessler syndrome, and “that we hope to prevent,” Berger said.

Close calls and near-misses

While rare, major collisions and explosions have happened a few times.

In 2009, an American satellite and Russian satellite crashed together, ending in nearly 2,000 bits of debris large enough to detect — at least 4 inches wide — with thousands more smaller bits.

In 2021, a Chinese satellite and a Russian rocket chunk collided, creating at least 37 pieces of debris large enough for ground systems to track.

And anti-satellite missile tests by Russia, China, and India have blown up dead spacecraft in orbit, sending thousands of chunks flying.

Each of these events created its own field of hazardous debris which still rockets around the planet today with potentially dire consequences.

For example, several times a year, astronauts on the International Space Station get debris alerts and prepare to evacuate if the station is struck. When this happens, spaceships docked to the station will burn their engines to push it out of the way.

Satellite operators often respond to warnings by moving their satellites out of the way. SpaceX told the FCC in July that its satellites had conducted nearly 50,000 collision-avoidance maneuvers in just the first half of the year, Space.com reported.

Unfortunately, not all satellites are maneuverable.

In March, NASA had to sit on its hands and watch as a long-dead Russian spacecraft careened toward the agency’s TIMED satellite, which was designed in the 1990s and doesn’t have the ability to move on command.

Luckily, the two spacecraft missed each other by 17 meters (56 feet) — not very far by space standards.

“That would’ve been a hypervelocity impact creating thousands of pieces of debris,” Berger said.

Daniel Baker, who directs the Laboratory for Atmospheric and Space Physics at UC Boulder, urged the US Congress to pass the ORBITS Act. The legislation would require federal agencies like NASA and the FCC to support technologies that can remove junk from orbit.

“I believe that we are watching the tragedy of the commons play out in low-Earth orbit right before our eyes,” Baker said in the briefing.

“We have to get serious about this and recognize that unless we do something, we are in imminent danger of making a whole part of our Earth environment unusable,” he added.