On missions to the International Space Station (ISS), astronauts no longer have trouble finding drinking water thanks to a new water reclamation system that recovers 98 percent of the effluent on board the ISS. This opens up new possibilities for future deep-space missions that will last months or even years.
Until now, astronauts have either carried their own supplies or relied on regular visits from cargo ships. As for waste, it was simply disposed of in various ways. However, deep space missions cannot afford this luxury.
A mission to Mars, for example, might last two years. That’s a lot of water to take with you at the rate of 3.8 liters per person per day. If a spacecraft has a crew of four, that’s at least about nine tons of water. It also ends up being tons of urine.
The ideal ship would be essentially self-sufficient with the ability to recycle air and water and grow its own food as a closed ecosystem. As a first step toward this, NASA is testing water recovery components of its Environmental Control and Life Support System (ECLSS) aboard the ISS.
The ECLSS system consists of a water recovery system, a water processing unit (WPA), a urine processing unit (UPA) and a brine processing unit (BPA) that extracts and recycles water on the space station through a series of steps from crew urine, breath and sweat.
Collecting water from the air is relatively easy with an advanced dehumidifier system. Urine, however, is a little more difficult to deal with. UPA removes most of the water with vacuum distillation, which leaves behind a urine brine that is as disgusting as it sounds. This goes to BPA, which uses special membrane technology and blows warm, dry air over the brine to evaporate the water, which is recovered just like water from breathing.
The reconstituted water then passes through a series of filters and a catalytic reactor to break down contaminants as sensors check for cleanliness before adding iodine to kill any germs present.
“The treatment is basically similar to some ground-based water distribution systems, just done in microgravity,” says Jill Williamson, ECLSS water subsystems manager. “The crew doesn’t drink urine; they drink water that’s been purified, filtered and purified in a way that’s cleaner than what we drink here on Earth. We have a lot of processes and a lot of on-the-ground testing to make sure that we are producing clean drinking water.”
Using the ECLSS system aboard the ISS allows astronauts to be less dependent on regular water supplies and improves their ability to conduct longer missions into deep space.