Get Ready for the “Kessler Syndrome” to Wreck Outer Space

Clive Thompson on 2021-11-17

Space junk in orbit is looking to become our next ecological mess

Illustration of a satellite breaking up, via the European Space Agency

Back in 1978, the astrophysicist Donald Kessler made an alarming prediction: Space junk could wreck our ability to keep satellites aloft.

In a fascinating paper, Kessler noted that “low earth orbit” — a region between 99 miles and 1,200 miles up — was getting pretty crowded. In 1978 there were already 3,866 objects being tracked in space. That included satellites used by scientists (say, to monitor weather) or spy agencies. It also included a lot of debris: Every time a rocket launches a satellite into orbit, it tends to leave stray bits of material.

The thing is, when objects are zooming through space about 2 km/s, even something as tiny as a chip of paint can smash through glass or steel. Pieces of debris become bullets.

What Kessler predicted is that sooner or later, objects in low-earth orbit would start colliding, and produce chain effects, like billiard balls colliding on a crowded pool table. If a piece of debris hit a satellite, it would produce more debris, which would to increase the risk of other collisions … and so on, and so on. At some point, you could reach a tipping point. There’d be so many chunks of debris that collisions would be inevitable, leaving low-earth orbit a junkyard where no satellites could survive.

Remember the scene in Wall-E where they blast off Earth, and the planet is utterly ringed with crap? That’s what Kessler worried about. Except in our situation the pieces of junk could be quite small — billions of objects the size of grains of sand, which is actually a lot harder to deal with, because you can’t see it coming.

In essence, Kessler predicted we could create an artificial asteroid belt of junk:

The result would be an exponential increase in the number of objects with time, creating a belt of debris around the earth. This process of mutual collisions is thought to have been responsible for creating most of the astroids from larger planetlike bodies.

Space folks began calling this the “Kessler Syndrome”. It was hard to predict when this might start happening. Kessler worried that conditions could be ripe by as early as 2000. Thankfully, that estimate turned out to be premature.

But wow, it looks like it might happen soon.

What’s happened recently that makes the “Kessler Syndrome” more likely?

A couple of things:

“Starlink Mission”, via Official SpaceX Photos

Way more satellites are going up

The pace at which satellites are going up in the sky is simply exploding. Back when Kessler wrote his paper in 1978, we humans were launching about 53 new satellites a year. Going to space was hard.

But now launches are an order of magnitude more common, and they’re increasing in pace rapidly. SpaceX in particular is launching oodles of satellites as it builds its orbital Internet-access service Starlink. In the last two years, it has put 1,740 satellites in low-earth orbit, with plans to eventually shoot 30,000 up there.

This is part of a larger trend, which is …

The privatization of outer space

The private sector is rapidly becoming the dominant actor in space. There’s a huge demand for satellite data — everyone wants better info about weather, crops, traffic patterns, tree coverage, emissions, you name it, on top of the explosive use of satellites for communication and Internet.

SpaceX’s remarkable innovations in rocketry (the leading folks, though others are following in their footsteps) have made it cheaper than ever to get a satellite into orbit. It is unlocking a huge pent-up demand for near-earth-orbit tech.

More launches mean not only more intentional objects in orbit but unintentional ones — bits of rocket parts and detritus from launches.

The militarization of outer space

Nation-states are increasingly regarding satellites as military targets — materials you can destroy to attack another country.

In the late 00s, the US and China each experimentally destroyed one of their own older satellites by ramming a projectile into it, to test how viable a form of attack this would be. It worked really well, alas. It also created thousands of new pieces of space junk.

Then just a few days ago, Russia joined the club by experimentally destroying one of its own old satellites — producing another 1,500 pieces of debris. As space becomes militarized, these sorts of attacks will be increasingly on the table.

One huge collision has already taken place

In 2009, an Iridium satellite collided with a defunct Russian satellite and boom: 2,000 large pieces of debris (god knows how many teensy ones), and a new problem for Iridium’s coverage. It was actually only nine years later than Kessler originally predicted the problem would start, which is in retrospect pretty good for an estimate made in 1978.

Satellite owners don’t like moving their satellites

If two satellites are at risk of collision, at least one of them has to move into a new orbit. But neither partner wants to do this, because moving your satellite burns fuel, and once you’re out of fuel the satellite can’t be maneuvered at all, making it useless. (FWIW, you’re supposed to use the last of the fuel to send it hurtling towards earth to burn up.)

The upshot is that satellite owners are now playing chicken in space. As I reported in a New Republic story last year …

Last fall, the European Space Agency realized one of SpaceX’s new Starlink satellites was on a dangerously close path to an ESA satellite. SpaceX said it had no plans to move the satellite; so the ESA decided to fire its thrusters and get clear. This high-stakes negotiation was conducted via email.

Playing chicken is not, as they would say in Silicon Valley, a scalable solution as tens of thousands of satellites flock into low-earth orbit.

“Space junk” by BobMacInnes

Many very knowledgeable folks are getting very unsettled by these trends. Last year I asked NASA’s then-head Jim Bridenstine about the risk of collisions. Now, Bridenstine was a big proponent of private-sector space activity, and also was a big proponent of SpaceX’s Starlink satellite swarms. Yet he responded bluntly that, yep, space is getting crowded faster than we know how to deal with it …

More satellite means more risk. And we as a nation have not yet caught up to the risk that currently exists in space.

Some other scientists I spoke to about it were flat-out flipping out.

How to clean up space?

No one yet knows how to entirely solve this problem.

LeoLab’s arrays for monitoring space debris

In the short run, we need the people who are launching satellites — both private-sector and governmental — to abide by the (mostly voluntary) guidelines on preventing extra debris from launches. Then we need more and better tracking systems for detecting where debris exists. (This tech is coming along — firms like Leo Labs can now track pieces of space junk down to a few centimeters.) It’ll also be crucial to figure out how to clean up space junk, and there are various experiments (using magnets, for example) to do that, though it’s very early days. I’m not holding my breath on that one.

Should companies today be launching fewer satellites? That depends on whether you think the services they’re offering are valuable enough to warrant the risks. After all, those satellites can do a lot of good: I’ve spoken to people who live in far-flung northern and rural regions who are getting fast Internet for the first time from Starlink, for example. They think the economic and cultural value of giving access to the world’s connectivity deserts is worth managing whatever risks might emerge in space.

The biggest thing that freaks me out is that this is an international problem with marketplace dynamics, so it’s … a hard one to address. You have to herd cats: Multiple governments, firms eagerly eyeing celestial profits.

History would suggest we’ll screw this up. Space is a commons, and we humans have a terrible track record of despoiling commons.

Space entrepreneurs pooh-pooh this concern. When I’ve reported on space junk, I’ve had plenty of venture capitalists and space entrepreneurs confidently assure me that the free market will solve it. It’s in their best interests, they insist, to keep low-earth orbit clean enough for commercial work. “Anyone who’s going to spend millions launching a satellite into space is also going to worry about keeping it safe,” one space operator told me. “We’re going to figure this out. It’ll self-regulate.”

Again, I’d point to the opposite lessons of history. For decades, free-market firms used the atmosphere and the ocean, and the soil as a place to dump pollution and emissions for decades. Governments let them get away with it. Many firms these days focus on only the next few quarters, not the next few decades. So I can easily imagine a space firm shrugging off massive long-term risk for the chance of a short-term profit. This is an area where a smart and strong regulatory hand is seriously needed; I’m not sure we’ll get it.

We’re used to thinking of outer space as a vast domain. How could we ever fill it up? But when it comes to low-earth orbit, as Donald Kessler intuited decades ago, space is surprisingly fragile.

Clive Thompson is a contributing writer for the New York Times Magazine, a columnist for Wired and Smithsonian magazines, and a regular contributor to Mother Jones. He’s the author of Coders: The Making of a New Tribe and the Remaking of the World, and Smarter Than You Think: How Technology is Changing our Minds for the Better. He’s @pomeranian99 on Twitter and Instagram.