Astronauts and cosmonauts have continuously occupied the International Space Station (ISS) since it began operation in 2000, orbiting Earth every 90 minutes.
During its tenure, the floating laboratory has been a melting pot for scientific experimentation, research into long-term space travel and international collaboration. So far, 280 astronauts have journeyed up to the station, representing no less than 23 countries.
Yet, as they say, all good things must come to an end. And so now at the end of the decade, the ISS will reach the end of its functional life.
But what do you do with a 430-tonne, football field-sized space station when it's no longer in use?
You can’t just abandon the ship; after the Moon, the ISS is the biggest thing orbiting Earth. If anything hit it the whole thing could come apart creating a shower of debris that would threaten other satellites.
How about pushing it a bit higher up so it’s out of the way? Not an option although NASA did consider it.
“The space station is a unique artefact whose historical value cannot be overstated. NASA considered this when determining if any part of the station could be salvaged for historical preservation or technical analysis,” the agency wrote in a white paper.
Ultimately, though, such a venture was deemed too expensive and complex to carry out.
That leaves us with one option for this groundbreaking feat of human ingenuity: total annihilation.
Enter Elon Musk, or, more specifically, his now dominant company SpaceX which on 26 June was officially awarded the contract by NASA to develop and deliver the ISS’s undertaker – a job worth an eye-watering $843 million to the private enterprise.
“Selecting a US Deorbit Vehicle for the International Space Station will help NASA and its international partners ensure a safe and responsible transition in low Earth orbit at the end of station operations,” Ken Bowersox, associate administrator for Space Operations Mission Directorate at NASA Headquarters in Washington, said in a statement.
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Though the plans are yet to be finalised, the basic idea is that the Deorbit Vehicle will act like a tug-boat, dragging the ISS down into the atmosphere where much of it will burn up on re-entry.
The sheer size of the ISS, though, means that parts of it will almost certainly survive the blast of heat. Care must therefore be taken to make sure that any parts that reach the surface do so in an unpopulated area.
"Most of the Earth is covered in water, and space scientists are well versed in applying changes to satellite orbits right up until the point of re-entry, to precisely control the path of a spacecraft," Dr Darren Baskill, astronomy lecturer at the University of Sussex, tells BBC Science Focus.
Baskill explains that the whole process will involve fine adjustments during the ISS's final orbits so scientists can almost guarantee it ends up in the right place, away from people.
"To use a sports analogy, rocket science is more curling than a penalty kick in football, where adjustments are made all along the projectile path," he says
There is a precedent for this. On 23 March 2003, Russia’s Mir space station met its demise at Point Nemo in the Pacific Ocean. At 2,688 kilometres from the nearest land, the same spot is a safe bet for where the ISS will be laid to rest too.
Is this the end of our life among the stars?
With the ISS’s days numbered, it marks the first time in more than two decades that humans will not maintain a permanent presence on the station. To put that in perspective, there are now fully grown adults who have literally never lived a day without someone whizzing about in the ISS overhead.
People will still be up there in space, of course. Unbeknownst to many in the West, China has had its own space station – Tiangong – in orbit since 2021 and hopes to keep it operational into the 2030s.
As for a US-backed station, NASA is looking to the private sector to house its astronauts more affordably in the post-ISS era.
The Commercial Low Earth Orbit Development (CLD) Program, for example, was unveiled by NASA in 2021, with hundreds of millions of dollars up for grabs for companies capable of developing new space stations. It sounds pricey, but considering the ISS cost about $150 billion to develop and $4 billion per year to operate, the move could prove quite savvy.
Besides, geo-orbits are old news. Much more ambitious is NASA’s Lunar Gateway project which, if successful, will put a space station in orbit around (no points for guessing this one) the Moon. With any luck, the first astronauts will enter the Gateway in 2028.
In short, the end of the ISS’s reign in low earth orbit brings with it uncertainty over the future of space habitation. It will almost certainly be dominated by the private sector and will likely see us stretch our wings beyond our planet.
"What the ISS has provided over the last 23 years is a platform to carry out a wide variety of experiments with a rapid turnover that simply cannot be carried out on the ground," Baskill says. "It has also fostered international cooperation, and inspired many into studying science further."
As Bowersox puts it, “The orbital laboratory remains a blueprint for science, exploration and partnerships in space for the benefit of all.”
About our expert
Darren Baskill is an outreach officer and lecturer in the Department of Physics and Astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
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