The International Space Station swerved to narrowly avoid Chinese space junk. A major impact would be a disaster.

• The International Space Station swerved to avoid a collision with space debris on Wednesday.
• Its orbit was changed by about 0.7 miles, per Russia's space agency, which organized the move.

NASA and Russia's space agency adjusted the course of the International Space station (ISS) to avoid a collision with debris that was headed.

The fragment was a remnant of a Chinese weather satellite that was destroyed in a missile test 15 years ago, Roscosmos, the space agency, said in a tweet on Wednesday, around the time it adjusted course.

The debris was due to approach the space station some time on Friday if it hadn't moved.

It was due to enter the "pizza box," a flat, rectangular zone 2.5 miles deep and 30 miles wide around the space station inside which any object is "close enough for concern," per NASA.

"It just makes sense to go ahead and do this burn and put this behind us so we can ensure the safety of the crew," said Joel Montalbano, NASA's space station manager, at a press conference on Tuesday, per The New York Times.

Neither NASA nor Roscosmos said how big the fragment was. While a small fragment may not have significantly damaged the station, large bits of space junk have the potential to cause catastrophic damage.

The maneuver raised the space station's orbit by about a mile (1.2 km), Roscmoscos said in a press release Thursday. The ISS fired its rockets for just over six minutes to get out of the way, the Conversation reported.

It took place just a day before Crew-3 mission astronauts Thomas Marshburn, Raja Chari, Kayla Barron, and Matthias Maurer arrived on the station.

Space junk: dangerous but 'highly manageable'

This is the 29th time the space station has had to dodge a piece of space junk, according to The Times.

Space debris is made up of bits of often defunct spacecrafts broken apart in orbit, per NASA. It can travel at speeds up to 17,500 mph, per NASA, about ten times the speed of a bullet.

Even a fleck of paint from a rocket can be dangerous at this speed - for instance, if it hits an observation dome.

"Space debris has the potential to cripple the ISS and kill the crew," Robert Frost, Instructor and Flight Controller at NASA, said in a blog post in 2019. But the risk is "highly managed," he said.

Ground-based crews track the biggest pieces of space junk to allow lead time to move the ISS out of the way, as can be seen in this Insider video.

Anything above a third of an inch (1 cm) could penetrate the shields of the ISS's crew modules, according to the ESA. Anything larger than 4 inches (10 cm) could shatter the station to pieces, per ESA.

In this instance, the space junk came from an anti-satellite test conducted in 2007, when China launched a missile against its own weather satellite - Fengyun-1C, per NASA.

That collision created about 3,500 pieces of large fragments and many other small ones, per NASA.

It wasn't immediately clear how big were the fragments predicted to cross paths with the ISS this Friday, but ground team only track bigger objects that are bigger than a softball, per NASA.

Collisions with smaller debris can also be damaging and are more unpredictable. In June, NASA said that a small fragment had punched a 0.2-inch (5-millimeter) hole in one of the ISS's robotic arms, Insider's Aylin Woodward previously reported.

Bigger fragments are also getting harder to track as an acceleration of space flight activity has led to a dramatic increase of fragments orbiting the planet.

Last year, NASA moved the ISS after detecting a piece of "unknown space debris" that would have flown within a mile of the space station Insider previously reported.

On that occasion, the astronauts still sealed themselves in a Soyuz rocke capsule, which could act as an escape pod in case the station was damaged.