1. Astronaut
An Earth-bound human uses about 80 gallons of water each day, but an ISS resident stretches just one for drinking, showering, and hydrating food. Astronauts’ bodies produce plenty of sweat droplets and carbon dioxide, both of which get sucked into vents, destined for recycling.
2. Urine recovery system (toilet)
When astronauts go number one, a slight vacuum in the toilet pulls urine into a low-pressure chamber, which forces the water to evaporate. This results in a salty brine, which resupply vehicles later jettison to burn up in the atmosphere, and water vapor, which heads off for decontamination.
3. Oxygen generating system
H₂O can perform double-duty if its atomic components separate. Behind the walls of the U.S. lab, an electrified membrane splits the molecules. Oxygen pumps into the cabin while hydrogen heads to a specialized reactor, a Sabatier, to become water again.
4. Sabatier reactor
Inside this machine, a blast of roughly 750°F heat breaks the bonds inside CO₂, forcing it into its constituent elements. The carbon and oxygen combine with hydrogen from the station’s oxygen generating system to make H₂O and methane (CH₄), the latter of which vents into space.
5. Water recovery system
Reclaimed water flows into a chamber in the U.S. Lab module, where an OxyClean-like reaction zaps odor-causing molecules and kills bacteria. A shot of iodine eliminates any potential stragglers, but astronauts test the water regularly just to be sure.
6. Water dispenser
Astronauts fill small metallic pouches and suck hydration through a straw, or squeeze water through a syringe onto dehydrated food. To shower, crewmembers pipe moisture directly onto their skin and hair, then mix in no-rinse shampoo to keep post-workout smells in check. This article was originally published in the Summer 2019 Make It Last issue of Popular Science.
