The history and future of the International Space Station

Earlier this year, NASA announced a plan to retire the International Space Station (ISS) and bring it down to Earth in 2031. The ISS is a huge achievement: a space station that has hosted decades of international collaboration and research. In this post, we take a quick look at the history of the ISS, and at its planned retirement.

How was the ISS built?

The International Space Station project grew out of NASA’s plans to construct a space station called Freedom, announced in 1984. Largely for budgetary reasons, Freedom was redesigned several times. The ISS is smaller than Freedom was intended to be, but it remains the largest artificial satellite in orbit around Earth, and a stunningly impressive achievement.

As the ‘International’ in the name suggests, the International Space Station is a remarkable collaboration between different nations. Five different space agencies across three different continents are involved in the ISS project: the USA’s NASA, Europe’s ESA, Japan’s JAXA, Canada’s CSA and Russia’s Roscosmos.

The ISS is about the size of a football field, and you’d be correct to think it’s hard to get anything that large into space. Because of this, the ISS was constructed over time in orbit, rather than being built entirely on Earth and then launched. It’s made of many modules, which were individually built and launched at different times, and were then attached to each other in space.

The Zarya module was the first part of the ISS to be launched, on 20 November 1998. The second module, Unity, was launched on 4 December 1998, and astronauts connected it to Zarya two days later: the first connection made in the gradual expansion of the ISS.

If you’d like to hear a firsthand account of the connection of Unity to Zarya, episode 73 of the NASA podcast Houston, We Have a Podcast features an interview with Jerry Ross, one of the astronauts personally involved in Unity’s installation. The episode is called ‘The International Space Station Begins: Part 2’, and you can find it here, along with a transcript of the interview.

The most recent modules, Nauka and Prichal, were launched as recently as 2021, and there are plans to add more modules this decade. Although the ISS is set to be deorbited in the 2030s, it’s still got plenty to do.

It’s actually possible to watch some present-day construction on the ISS. Earlier this month, on 3 December 2022, astronauts Frank Rubio and Josh Cassada installed a new solar array on the space station, and NASA livestreamed the seven-hour operation. You can watch it here on YouTube, or, if you don’t have seven hours to spare, the BBC has condensed a few snippets into a fifty-second video over here.

What is the ISS used for?

At heart, the ISS is a space laboratory. The experiments conducted there can teach us more about the impact of space radiation, how humans can live in space for long periods, how to create better environments and equipment for astronauts, and how to grow plants in space.

Experiments conducted on the ISS can also benefit the people on Earth. The lack of gravity has made it possible to research new methods of delivering cancer treatment, and the ISS SERVIR Environmental Research and Visualization System (ISERV) was used for Earth photography in 2013 and 2014. In addition to telling us more about our environment, these photographs sometimes captured large-scale disasters and were used to assess how responders could help.

The ISS is permanently crewed, which means it’s one of only two places outside Earth you’ll always find humans; the other is the Chinese space station Tiangong. The NASA website keeps track of who’s on the ISS; right now, in late 2022, it’s occupied by Frank Rubio, Nicole Mann, Josh Cassada, Koichi Wakata, Sergey Prokopyev, Dmitri Petelin and Anna Kikina.

Crew members are cycled out on a regular basis, and a mission to the ISS tends to last about six months. The ISS is an exciting place to work, but being in space for long periods can be psychologically difficult, and we’ve written before about the health impact of living in low gravity.

How to see the ISS

The ISS is moving around our planet at incredible speed, about 400 kilometres above us. It orbits the Earth fifteen times per day at almost 28,000 kilometres per hour, taking just over an hour and a half on each lap.

If the ISS happens to be passing overhead shortly after sunset or before sunrise, when the sky is dark but the station isn’t in Earth’s shadow, you can see it just by looking up at the night sky. It’s easy to spot; it’s very high up, very fast-moving and very bright. The NASA website Spot the Station can tell you when and where the station will be visible.

Seeing the inside of the ISS in person is a bit trickier, of course. Google has captured Street View imagery of the space station, though, so you can explore it on Google Earth. Remember to look up; there’s no up or down in space, so the ‘ceiling’ is just another wall and often has equipment on it.

The future of the ISS

The ISS still has years of scientific work ahead of it; if you want to see it overhead, you’ve still got almost a decade to do so. But, unfortunately, it can’t keep working forever.

Because it’s in low Earth orbit, the ISS experiences small amounts of atmospheric drag, which slow it down over time. Unlike higher-orbiting satellites, the ISS has to be boosted on a regular basis to keep it in orbit. This means that it can’t just stay in space once it’s stopped fulfilling its role; if we stopped maintaining it, it would fall to Earth before long.

It’s potentially dangerous for a satellite to fall out of the sky without a plan in place. Because of this, NASA intends to bring the ISS down to Earth in a more controlled fashion, rather than letting it fall naturally.

Once the last crew has left the space station, operators on Earth will drop the ISS into the atmosphere, aiming for the debris that survives the friction of the fall to land around Point Nemo in the South Pacific Ocean: the point in the ocean that’s furthest from solid ground. Hundreds of satellites have already been crashed at this point, far from any inhabited locations.

If you’d like to know more about the deorbiting of the ISS, NASA has an FAQ page about the subject. If you’d like to know more about satellite disposal in general, meanwhile, take a look at our article ‘What happens to old satellites?

Cover image: JAXA/Koichi Wakata

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