Water is one of the most plentiful resources on our planet, with roughly two-thirds of the Earth’s surface underwater. Its abundance is critical to our continued survival, with the average person needing to drink approximately half a gallon of water a day. As such, we – in the developed world at least – are only a tap away from a ready supply of water. We can buy a bottle of water from a corner shop for as little as 99p.

See related Space shotgun isn’t a return to armed astronauts Alcohol in space: From communion wine to zero-gravity whisky For the International Space Station (ISS), orbiting the Earth at a mere 17,100mph, the nearest corner shop is approximately 230 miles away, and not exactly easy to reach. You can’t just pop out of the door and nip to the shops. Not unless you wear a vacuum suit and have a space rocket and lander module to hand.

Living in such a remote and inhospitable location, water becomes something of a commodity on board the ISS, where it can cost approximately $10,000 USD (about £7,000) for a bottle of water. To put this into perspective, a serving of water costing $3,000 (£2,000) aboard the ISS is hundreds of times more expensive than a pint of premium lager down your local pub. However, the view is undoubtedly better on board the ISS.

Wait… how much?

“Cargo space is at a premium, and every item needs to be costed to ensure value for money”

Much of the cost stems from how expensive it is to provide the ISS with essential supplies. Each supply run to the ISS costs several million dollars, with the launch itself costing up to half a million dollars. As such, cargo space is at a premium, and every item needs to be costed to ensure value for money, looking at each item’s weight, volume and necessity.

Originally, the Space Shuttle program would provide regular supply runs to the ISS. This was despite the Space Shuttle being expensive to run, costing $500,000,000 (nearly £350,000,000) to launch, compared with the cost of $300,000,000 (over £200,000,000) to launch a smaller rocket like Space-X or the Orbital ATK. However, the Space Shuttle could carry 50,000lb (over 20 tonnes) of cargo, compared with 5,000lb on the rockets. This is due to the dedicated cargo space on board the Space Shuttle.

“For every shuttle I launched into space, I now have to send ten smaller rockets from Russia or the United States,” says Dr Ravi Margasahayam, a Payload Safety Engineer with NASA and co-chair for the Ground Safety Review panel for the International Space Station.

As such, it has become increasingly cost-prohibitive to supply the ISS directly with all of their water requirements. Originally, NASA would use the space shuttle to supply the ISS with water every two to three months, with the water carried in a series of bags, each weighing 90lb (approximately 40kg) each.

As the systems have become more efficient, NASA now only needs to send a rocket every three to six months. This also improves safety, as there have been accidents with Russian, Space X-7 and Orbital ATK Antares launches.

Each supply trip carries up to 400 gallons of water. This water is not intended to meet all of the astronauts’ needs until the next supply run, but is instead intended to top up the water reserves of the ISS. Rather than relying solely on water provided by NASA and Roscosmos (the Russian Federal Space Agency), the ISS implements a series of water-harvesting and recycling systems to provide the astronauts with H20.

Nothing wasted

“Nothing is left out. Even the laboratory rats contribute their urine”

Since it’s such a precious resource in space, the water reclamation systems harvest moisture from all possible sources on board the ISS, from condensation and humidity, through shower and oral hygiene water, to perspiration and urine. Nothing is left out. Even the laboratory rats contribute their urine. “One human is about 72 rats, as far as water reclamation goes,” says Margasahayam.

At the moment, the water reclamation systems harvest 93% of the waste water, with the remaining 7% lost through airlocks and grime. Nonetheless, the ISS recycles approximately 3.6 gallons of water every day.

As the water reclamation and recycling systems are shared equally by both sides, it is inevitable that American astronauts will have consumed Russian wee and Russian astronauts will have consumed American wee, which is pretty much a first in international relations.

“Despite these less-than-appetising sources of water, the water on board the ISS is purer than our drinking water on Earth”

Despite these less-than-appetising sources of water, the water on board the ISS is purer than our drinking water on Earth. This is due to the ISS’s water-recycling process, which partly mimics our planet’s process of water of evaporation and precipitation. Instead of simply filtering the water, the waste water is collected and reduced to its component atoms, whereupon the hydrogen (H) and oxygen (O) atoms are combined together to create fresh water. As such, the astronauts have no problem drinking the water, despite its less-than-palatable origins as sweat and urine.

As well as the water-recycling and reclamation systems on the International Space Station, NASA is using a method called the Sabatier reaction to create water from hydrogen and exhaled carbon dioxide. The hydrogen is a by-product of the Oxygen Generation System, which uses electrolysis to convert water into oxygen and hydrogen. Previously, this hydrogen was vented into space, as it is dangerous to store in large quantities, but it is now fed directly into the Sabatier Reactor.

Looking ahead, these Sabatier systems will play a crucial role in the planned Mars missions in the future. Given that Mars is approximately 225,000,000km (nearly 140,000,000 miles) away, it can take six to nine months to reach the red planet. When you factor in the return journey as well, it could be 18 months or more before the astronauts return to Earth.

Preparing for Mars

For this reason, NASA is not only looking at making water-reclamation and recycling systems ever more efficient, but researching water-producing systems as well. “We can generate methane [as well as water] from the Sabatier reaction, and methane can be combined with carbon dioxide on Mars to convert it into water,” explains Margasahayam.

“What was once a waste by-product of the oxygen production process now becomes a means by which a top-up supply of water can be produced to meet the astronauts’ needs”

For the ISS, what was once a waste by-product of the oxygen production process now becomes a means by which a top-up supply of water can be produced to meet the astronauts’ needs. This in turn reduces the amount of water the ISS needs from Earth.

“Any time you do not take more weight, you are not only reducing volume of the payload, but you are also reducing costs,” explains Margasahayam. “You can use that volume to send something else into space, such as food or experiments.”

So, the next time you complain about the cost of a beer at your local pub, just think how much water costs on board the ISS, and drink your pint without complaint.

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Images: Neil Tackaberry and NASA used under Creative Commons