On Fridays I generally write about sustainable buildings and architecture. Does the International Space Station count as architecture? Or a building for that matter? I’m not sure, but I do know that there’s a good reason for including it: it’s a neat example of circular principles and closed loops.
It’s hugely expensive to get things into orbit. According to , which I’ve been reading with my son, it costs $5,000 per kilo to deliver things to the ISS. It doesn’t matter if it’s a kilo of water or of gold – it’s just really expensive to lift anything out of earth’s gravity. So once you’ve got something up there, you want to keep it and reuse it.
. Water is precious on a space station, so astronauts’ urine is processed by filters and a high temperature catalytic reactor, turning it back into pure and drinkable water. Any water used for washing or for brushing teeth also gets reused. In the Russian part of the station, another unit captures moisture from the air, so that sweat and breath from the occupants don’t go to waste either.
If that sounds a little grim, it’s only because of the unusual tightness of the loop. We’re all drinking water that’s been around for billions of years and has been through people and plants and animals before. And besides, NASA can’t risk its astronauts getting sick, so the water that comes out of the dispenser on ISS is some of the purest in the solar system.
It’s doubly important to reuse water, because through electrolysis. A litre of water a day per person is split into oxygen and hydrogen. The hydrogen used to be vented into space. It is now saved, combined with CO2 from the air and turned into water and methane. The water goes back into the system and the methane is vented instead.
All of this is done by machines at the moment. A lot of it could be done by plants, and there are ongoing experiments in generating oxygen and cleaning the air using plants. It would need a large and specialist module, which would be hugely expensive. Perhaps it will happen eventually, and at that point the ISS would be closer to a truly sustainable system, but for the moment machines are far more compact and dependable.
As you can see clearly in the photos, the ISS uses solar power. Its 8 solar arrays fold up like a concertina for transport, and unfold into an area half the size of a football pitch altogether. The wings can be angled to optimise sunlight, and since the station does need to pass out of direct sunlight, batteries are used to store excess power. The nickel-hydrogen batteries are currently being updated to lithium-ion batteries, which can store twice as much power in the same space.
The ISS is a microcosm of our planet – it relies on the sun for its energy, and on systems to maintain the atmosphere and water supplies. On earth we have natural systems that run these services for us, and they are easily taken for granted. We rarely stop to think about them, and only pay attention when they break down – when a drought interrupts the water cycle we depend on, for example. When we ignore these cycles, we can drift into bad collective habits that eventually begin to destabilise them, as we’ve done with the carbon cycle and the climate, as well as the nitrogen and phosphorus cycles.
By looking at the International Space Station and the huge amount of technology needed to create liveable conditions for human beings, we are reminded of just how much nature provides for us on our home planet. And if we pay a little more attention to these natural systems, perhaps we’ll take better care of them.