The Trouble with Space Junk

I remember when I first saw the movie “Gravity” in theaters I was blown away by the incredible visuals. It’s full of inaccuracies, but it’s in service to a fantastically-executed story, so I’ll give it a pass. It also has, as the root cause of all the action, a real and genuine problem that companies and space agencies around the world are grappling with: space debris.

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Spoilers for the beginning of the film: the movie starts with several astronauts out by the Hubble Space Telescope in a fictional space shuttle. They get an alert from Houston that Russia has shot down a spy satellite and there is a wave of debris heading their way. Communications are lost as this wave of debris begins to wipe out satellites, and eventually takes out the space shuttle and Hubble, stranding our heroes in space. All very horrifying and epic and awesome.

The thing is, it’s not entirely a fictional scenario. Although the timescale used in the movie is unrealistic, the basic concept is one that represents an entirely too-possible nightmare for anyone who likes to put things in orbit or use things in orbit. So…everyone. Let’s take a look at the space debris problem.

What’s the Issue?

Humanity began putting things into Earth orbit with the launch of Sputnik in October 1957. Three months after it launched, Sputnik re-entered Earth’s atmosphere and burned up. This wasn’t on purpose, it’s just how physics made things go. But that’s not always the case. It depends on the orbital height and speed of your satellite.

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To put this in perspective, the fourth object ever successfully launched into orbit, the wee satellite Vanguard 1, lifted off on March 17, 1958 and took up residence in an elliptical orbit that brings it anywhere from 400-2,400 miles away from Earth. It’s still there. 

The satellite has been dead since 1964, but physics won’t pull this thing down into Earth’s atmosphere to burn up until sometime around the year 2200, give or take a few decades. Part of the rocket that carried it up there is also still in orbit. You can consider them the beginning of the space debris problem.

Since 1957 humans have launched thousands of satellites. Our very society has come to depend on them for everything from communication to weather monitoring to navigation to entertainment. One of them is the International Space Station, the largest thing in Earth orbit (other than, you know, the Moon). Many of these things in orbit are long dead. In some cases, as with Vanguard 1, there are pieces of the rockets that launched these satellites up there with them.

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And that’s the dead stuff. The Union of Concerned Scientists calculated that, at the end of 2022, there were 6,718 active satellites in orbit around Earth, with each of the last three years seeing a 30% jump in the number of satellites as companies like SpaceX and OneWeb launch ever-growing constellations of spacecraft. 

 The actual number of objects in Earth orbit far exceeds the number of things that have been launched, since a number of those objects are no longer in one piece and each individual fragment counts on its own. According to the European Space Agency, there are about 34,500 pieces of space debris being tracked in Earth orbit. And the untracked number may be far, far higher—the ESA officially lists an estimate of 1 trillion objects over 1 cm in size.

Why Worry?

1 cm doesn’t seem like much. Nothing that size will have much mass—some of them may even be just flecks of paint. That might beg the question of why we care about the little stuff. Shouldn’t we just be focusing on those big, dead satellites if we’re so worried about clutter in space?

You’re right that under normal circumstances a 1 cm fleck of paint isn’t going to hurt anything. But even a tiny, tiny bit of mass will cause damage if you get it going fast enough. That is, after all, how bullets work. And things in orbit are going fast. They have to. If you’re in orbit and you slow down enough, you won’t be in orbit anymore. On average things are moving around 17,500 mph up there (that’s about ten times faster than a bullet). At that speed even a paint fleck will wreck your whole day.

Now imagine a trillion such tiny things whizzing around in Earth orbit, under no control but that of physics. Earth orbit suddenly starts to look like a shooting gallery. The more debris there is, the more additional debris it can generate via collisions, and this is where the situation at the beginning of “Gravity” begins to look more realistic. We call that situation a Kessler Cascade, when the shredding of satellites becomes a catastrophic and unstoppable feedback loop, and we would to avoid it at all costs. But the problem is only getting worse.

The Growing Problem

Obviously with the advent of the age of satellite constellations, the number of things in orbit is going way, way up. That’s not really the issue though—all of those new satellites have active control systems and fall under modern regulations that require that anything that goes up must be able to be got back down. No modern satellites are allowed to remain as space debris. Not for long anyway. Of course, the more stuff there is up there, the more targets there are.

In 2009 the first known collision between two satellites occurred, when an active commercial satellite, Iridium 33, collided with a dead military satellite, Kosmos 2251. 

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Their relative speeds meant the collision happened at 26,000 mph. What started out as two large objects in orbit became thousands of smaller objects as the satellites obliterated each other. Sometimes it’s not two satellites that hit each other, but a satellite and a small piece of something or other. In the process of drafting this post, a breaking news report announced the destruction of a thirty-year-old defunct Soviet satellite by piece of debris too tiny to track. And that’s the stuff that happens by accident! There’s also…the other kind.

The governments of the world are uneasy about satellites. Not their own, of course, but anybody else’s. Every now and again a country will remind the rest of the world what it can do to any satellite it views as a threat by demonstrating anti-satellite (ASAT) missiles. These, as you might guess, are missiles that can be launched from the ground to take out satellites in orbit. As you can also probably guess, blowing up a satellite makes, well, a lot of pieces.

While some ASAT tests carried out in recent years were deliberately carried out on objects low enough that gravity would quickly deorbit the debris, there are two that have been…problematic. In 2007, China demonstrated an ASAT weapon by destroying an old weather satellite. This satellite, which orbited too high for easy debris deorbiting, was demolished into over 3,500 trackable pieces—the largest field of space debris ever created (that we know of). More than half of this is expected to remain in orbit for decades.

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Then, in 2021, Russia destroyed an old intelligence satellite, producing at least 1,500 pieces of trackable debris. The big problem with this one is that this debris was right in the path of the International Space Station. The residents of humanity’s orbital outpost were woken up and told to immediately shelter in place in the space capsules they rode to orbit, ready for separation and return to Earth at a moment’s notice. The ISS survived the day, but will be continually dodging the leftovers of this particular ASAT test for the rest of its life (among many other pieces of debris the station has to dodge). 

Nobody really wants a bunch of dead astronauts because the ISS got punctured. Or a Kessler Cascade of shredded satellites. Heck, I’ll go out on a limb and say nobody wants their music and movie streaming interrupted. To that end, an increasing number of nations have committed to banning ASAT tests. In April 2022, the United States officially banned any future American ASAT tests. In December of that year, 155 countries voted in favor of a UN resolution for a similar ban. And in August 2023 the member states of the European Union officially pledged to never conduct such a test.

So What Now?

That’s all well and good but it still leaves the problem of the stuff that’s already up there. There’s a lot of trash that isn’t going to come down on its own anytime soon. So what’s to be done about it? At this precise moment in time: nothing. But hopefully that’s going to change.

The threat of a Kessler cascade is real and recognized, and a number of companies, organizations, and space agencies are thinking about how to clean up Earth orbit. Ideas for debris removal have included lasers, nets, bags, sails, and harpoons, some of which have already been tested in space.

In 2019 the European Space Agency awarded the world’s first space debris removal contract to a Swiss startup called ClearSpace SA. The spacecraft being built as a result of this contract, ClearSpace-1, was intended to launch in 2026 to test the removal of a large piece of space debris by capturing a piece of a Vespa rocket used in a 2013 launch in a giant claw and then pushing itself, with its captive, into the atmosphere for a destructive deorbit. 

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On August 10, 2023, the ESA’s Space Debris Office got a call from a US military unit that tracks space debris. ClearSpace-1’s target, the Vespa rocket piece, appeared to suddenly have additional pieces around it. The most likely explanation is that the rocket fragment was nailed by a small, untracked piece of space junk and is now itself in pieces. That story should be next to the word “irony” in the dictionary.

The construction of ClearSpace-1 continues. If the Vespa rocket fragment will no longer serve as an adequate test target, the ESA will find another one. The groups working on nets and harpoons will keep working. Space junk can feel like a somewhat comical issue, but the consequences of not figuring out how to solve this problem are pretty dire, after all, if we want our satellite-dependent civilization to continue. Which would, you know, be nice.