The end of the space shuttle era has prompted all manner of questions. Was the shuttle worth the cost? What would we miss most? And, of course, that perennial favorite of grade-schoolers: How do astronauts go to the bathroom?
Only this time around, NASA has some interesting news to share on that last question. One of the four astronauts on the Atlantis will be testing a device that Wired calls “a textbook-sized kit that can convert urine into drinkable water.” (The astronaut will actually be running an “experimental fluid,” not his or her urine, through the device.) The device works using a process called forward osmosis, by which the drinkable bits of urine slowly pass from an outer bag into an inner one.
Wired’s slideshow, which is worth checking out, walks us through the process. A special electrolyte solution gets injected into a semi-permeable inner bag. Dirty fluid is then added to an outer bag. The fact that the electrolyte solution has a much greater osmotic pressure drives it to draw (cleanish) water molecules out of the dirty fluid and into the inner part of the bag. The whole process takes four to six hours, at the end of which you have your own jug of UrineAde. The device isn’t perfect, sadly; urea, a chemical in your pee that you really don’t want to drink, still manages to get through. The only person who has been brave enough to try the drink has been a Japanese TV crew member, who did so against NASA’s advice. “He’s still alive and walking around,” NASA scientist Howard Levine told Wired. “He said it tasted like Capri Sun.”
As always, of course, there are science-fiction precedents; Levine cites Dune, while what leapt to mind for me was, inevitably, the personal favorite Waterworld. What might surprise you, though, is that there are science-fact precedents here as well. Astronauts, in fact, already have sampled recycled urine water in space, back in 2009–only, it was with a different device, one that uses an external power source. In our ever-greening world, that’s cheating. The discerning, environmentally conscious astronaut only drinks urine that’s organic, locally sourced, and purified passively and sustainably through forward osmosis.
When designing an embedded system choosing which tools to use often comes down to building a custom solution or buying off-the-shelf tools.