Why satellite mega-constellations are a threat to the future of space

When India shot down one of its own satellites with a missile this week, NASA administrator Jim Bridenstine was not impressed. “Creating debris fields intentionally is wrong … If we wreck space, we’re not getting it back,” he said.

He was referring to the growing problem of space junk: dead satellites, leftover rockets, and debris from previous collisions that threaten operating satellites, human spaceflight, and even the International Space Station.

It’s still too early to have good enough data on the debris cloud from India’s anti-satellite test, and tracking firms will be monitoring the area closely. The Pentagon has its eye on 250 separate pieces at the moment, an official told Reuters. But while it is likely that the collision created a cloud of metal fragments, it happened at a relatively low altitude. The majority will be dragged down into Earth’s atmosphere within months.

And while Bridenstine wasn’t happy about the India test, space debris experts currently have much bigger concerns. Proposed “mega-constellations” of satellites that sit higher up are likely to cause far greater and longer-lasting problems.

Around half of all the debris in space today comes from just two events: a 2007 anti-satellite test by the Chinese government, and an accidental 2009 collision between two satellites.

But there are plans to make low Earth orbit vastly more crowded. For example, satellite startup OneWeb wants to put 900 small satellites into orbit to provide broadband internet connections to places where it’s not currently available. SpaceX, meanwhile, has been granted approval to scatter 12,000 satellites through low Earth and very low Earth orbit. Other firms, such as Telesat and LeoSat, have similar, smaller-scale plans.

This sudden influx of new arrivals has the potential to cause serious problems. In a paper presented at the 69th International Astronautical Congress in Bremen, Germany, last October, Glenn Peterson, a researcher at the Aerospace Corporation,…