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Satellite Swarms Could Eat Themselves

The more satellites we launch without retiring old ones, the more there are to collide with one another.

What goes up, may come down in pieces—and cause some trouble in the process.

As hardware prices and launch costs fall, there’s an increasing trend to launch swarms of satellites into space to monitor our planet and transmit data. But some academics are concerned that the rising numbers may make an existing space junk problem far worse.

At the end of 2016, it was estimated that 1,459 operating satellites were in orbit around Earth. But that number looks set to rise quickly, as companies continue to launch swarms of smaller spacecraft. Earlier this year, for instance, Planet Labs popped 88 of its tiny satellites into space to photograph the planet below.

That shouldn't be much of a problem, you might think. After all, each of the Planet Labs satellites is small—about the size of a backpack and around nine pounds in weight. But other organizations have grander visions. SpaceX plans to launch 4,425 satellites to blanket the planet in Internet connectivity. Samsung has described how 4,600 could enable it to do a similar job, and Boeing also wants in on the idea with a 3,000-strong fleet of its own.

The prospect of these huge swarms of satellites has been keeping Hugh Lewis, from the University of Southampton in the U.K., up at night. His concern: that an increasing number of satellites in orbit increases the risk of collisions, and current rules stipulating that old satellites be brought back down within 25 years of the end of their service life won’t be enough to stop the problem from escalating out of control.

Instead of simply imagining what might happen, Lewis simulated how 1,000 extra satellites in orbit might interact with each other over the coming 200 years. His supercomputer calculations, which will be presented at a European Space Agency conference this week, suggest there could be a 50 percent increase in the number of satellite collisions if existing guidelines for decommissioning are followed. Speaking to the BBC, Lewis explained the origin of the problem:

What we found was that when you put the constellation satellites on to a disposal orbit, they intersect with objects below them. And if they take 25 years to pass through those lower altitudes, there is a good chance that they will have collisions with objects in the background population on the way down. But by reducing the 25 years to five years, you greatly minimise the chances of those interactions taking place.

You might think that a 50 percent increase doesn’t sound like a great deal, all things considered. But as New Scientist points out, it could put us closer than ever to the long-feared Kessler syndrome: a cascade of collisons that ultimately gives rise to a space junk belt encircling Earth. That could write off many existing satellites, as well as making new launches and space exploration far more difficult than today.

There have been some radical ideas for clearing the ensuing debris, including a rocket that feasts on the stuff. But Lewis has a simpler suggestion: simply enforce a five-year retirement window, rather than the current 25 years. For the sake of the satellite swarms and our Internet connections, that might be a good idea.

(Read more:  BBC, New Scientist, “SpaceX’s Plan to Provide Internet from Orbit Edges Closer to Launch,” “The Startup That’s in Charge of the Biggest Private Satellite Fleet,” “Junk-Eating Rocket Engine Could Clear Space Debris”)

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