How to Destroy a Space Station

The end of the International Space Station will soon be upon us. What should we do with it?

The International Space Station, as seen by a departing Dragon capsule. Image credit: NASA Johnson

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What do you do with an old space station? In the early years, when nations first started putting stations in orbit, the question seemed rather redundant. None of them lasted long. Salyut-1, the first, survived less than a year in orbit, and hosted just a single ill-fated crew of cosmonauts. Its successor, Salyut-2, made it through thirteen days before it was ripped apart by a cloud of debris and sent tumbling back to Earth.

Fortunately those of later years fared better, and one - Mir - set a record of fifteen years in orbit in 2001. Today just two stations exist, both of which have clocked up multiple years in space. The younger of the two, the Chinese Tiangong-2, is now in its third year of operation. The other, the International Space Station, has exceeded a quarter century in orbit.

In this the International Space Station has surpassed all expectations. Designers originally foresaw a lifespan of fifteen years: impressive by the standards of the time, but one that would have seen it abandoned in 2013. Operators now hope to keep it going until 2031, by which time it will have spent over thirty years in space. Conceivably, if nothing serious breaks, it might last even longer.

The question, though, is what to do with it after it finishes work. At some point, whether by design or accident, the station will be left uninhabited: when it is, the countries that run it will need to figure out what to do with it. It is, simply put, the largest and most expensive thing ever built in space. It has hosted hundreds of astronauts, consumed billions of dollars and maintained an uneasy relationship between Russia and the West, even as war raged on the planet below.

It deserves, if nothing else, a proper send off. It should, some have said, be preserved, and so serve as a marker of humanity’s first steps beyond our planet. Others see it as too valuable to waste, and suggest scavenging it for parts; allowing bits of it, at least, to live on in another form. Or, as NASA now seems to prefer, it could be given a strange and lonely afterlife, one that would first see it plunged deep into the great Southern Ocean.

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Option 1: Let It Be

The easiest option, of course, is to simply abandon the station. The astronauts pack up, depart on their spaceships and leave the empty space station flying around the Earth. With no one left onboard, operators no longer need to worry about maintaining its systems, and everyone can move on to thinking about other stuff.

This, after all, is what happened to the first American space station, Skylab. After the final crew left in 1974, the station was parked in orbit and abandoned. Despite tentative plans to reoccupy the station, perhaps with the help of the then new space shuttle, nobody ever stepped on board again.

When it was abandoned, Skylab was left in an orbit some four hundred kilometres high. The air up there was thin, but still dense enough to create a light wind that blew against the orbiting station. Over time that wind dragged it down, and eventually pulled them into the thicker layers of the atmosphere.

Skylab took five years to fall into the atmosphere. When it did it burned under the fierce heat of reentry, and then ripped apart just fifteen kilometres above the Indian Ocean. Debris from the station scattered across Australia, with large chunks of it landing in fortunately uninhabited areas.

NASA got lucky back then: an airliner pilot reported seeing the debris fly over him, and the path of the station had earlier crossed the eastern coast of the United States. Had it come down just half an hour or so sooner, the outcome could have been very different.

The International Space Station, of course, is much larger than Skylab. If it were abandoned and left to fall back to Earth by itself, the risks of a terrible accident are high. Big pieces of it are likely to hit the surface, and without control they could fall over large swathes of the planet. NASA, understandably, wishes to avoid this outcome.

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Option 2: Send It To The Moon

If leaving the space station to plunge wildly back to Earth is a bad idea, then why not do the reverse? Couldn’t we just stick some boosters on the thing, raise its orbit and perhaps leave it to eternally circle the Moon?

After all, the space station is one of the most expensive things ever constructed by humankind. Why would we spend all that money just to have it burn up in the atmosphere? Why not preserve it, and leave it as some kind of celestial museum for future sightseers? 

Believe it or not, this idea has been seriously entertained. Proposals and studies have examined how the space station could be sent to a high orbit, and thus preserved in a safe place with no danger of falling back to Earth.

NASA’s analysis on the subject reckons the station could be preserved for a thousand years by boosting its orbit to a height of nine hundred kilometres, roughly twice its current altitude. Doing so is technically possible, though it would take a lot of fuel. A special vehicle would have to be built, and perhaps some kind of in-orbit refuelling would be needed to raise it high enough.

That might be expensive, but it is doable. And it wouldn’t necessarily have to be done all at once. As long as the space station can be raised enough - say to six hundred kilometres - NASA can buy time to develop any missing hardware. 

The real problem, however, is space debris. The station has so far spent most of its time below five hundred kilometres altitude, a region that is relatively free of debris. A little higher, and especially above six hundred kilometres, the amount of debris rises fast. By the time the station reaches eight hundred kilometres, calculations suggest it would suffer a serious debris strike once every four years.

Such a strike would risk ripping the station apart, defeating any effort to preserve it. Even worse, such an event would scatter more debris, perhaps ushering in the dreaded Kessler Syndrome. That would leave entire orbits unusable for centuries.

Raising the station, then, would be a difficult and dangerous task. Though NASA probably could place it thousands of kilometres high, there is no guarantee it would survive the harsh realities of space. Preserving it as a museum, clearly, is a no go.

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Option 3: Recycle It

What about reusing it, then? After all, the hardest part of space is actually putting things in orbit. The station, if NASA no longer wants it, could perhaps be salvaged and used for other purposes. A commercial operator could take it over, or it could be taken apart module by module and then combined into new space stations.

Russia, for example, once proposed separating its modules from the station. After, they would serve as the core of a new Russian space station, which would then be expanded with a handful of newly launched modules. This idea, they eventually decided, was infeasible. The modules are, anyway, too old and damaged now to be of much use in a new station.

Axiom, an American company seeking to build its own station, has a similar plan. In the coming years Axiom hopes to attach four modules of its own to the International Space Station. These would be dedicated to commercial and scientific activities, and Axiom would staff them with their own astronauts. Eventually they would separate from the station, and then go on to form an independent space station of their own.

Other companies have suggested using the space station as a source of scrap metal. Conceivably parts of it could be melted down in orbit, and then reforged to build other things. This would make use of the material in orbit, but the technological feasibility is uncertain. Nothing like it - and certainly nothing of this scale - has ever been attempted before.

NASA, for its part, has concluded that recycling the station is infeasible. None of the proposals it examined make sense, it says, and so the station must come down. The only question is how to do that.

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Option 4: Crash It On Purpose

Sometime towards the end of this decade, then, NASA will launch a special spacecraft. After arriving at the space station it will dock, and then wait for a year or so while the station drifts lower. At some point the final crew of astronauts will take their leave, and the space station, after more than twenty-five years of service, will be shut down.

Shortly afterwards the docked spacecraft will fire a set of powerful engines, and so carefully steer the station towards a remote stretch of the Pacific Ocean. The space station will burn, and then it will freeze. Whatever survives of it will plunge deep into the ocean, and there it will remain.

At the end of June, NASA announced that SpaceX will build this special spacecraft, a vehicle that they have based on their successful Dragon Capsule. Just like a regular Dragon, it will fly up to the station and dock at one of the available ports. But unlike the others, this one will be fitted with a module holding dozens of powerful engines. When the time comes to bring the station down, those engines will fire together, and thus give it the final, controlled push Earthwards.

In the end the station is likely to find itself deep under the southern Pacific Ocean, in a remote region far from any inhabited land. Dozens of other spacecraft already lie there, two and a half miles deep, including Mir, the Russian space station that returned to Earth in 2001. Exactly when the International Space Station will join them remains to be seen. But one thing seems in little doubt: it will, eventually, do so.