Even on the harsh deserts of Arrakis, the the water recycling capacity of a stillsuit prevent the wearer from would only lose a thimbleful of water a day. If you figure a thimble holds about 10 milliliters of water, and an astronaut normally consumes 2.7 liters of water per day through eating and drinking, that’s only a loss of .4% of the body’s daily water. Pretty impressive for a desert race with long life but limited resources. (In case this wasn’t clear, I’m talking about George Frank Herbert’s Dune here.)
Until recently, there was no need for us to try and engage with this sort of water recycling technology. In general, water has been plentiful in this world, and if it wasn't we just piped it in. (I just re-saw Chinatown, so I'm feeling up on all this.) But increasingly short supplies of water in the American southwest and elsewhere have turned eyes to water recyling as at least a part of the long-term water supply solution. But to take a more extreme situation, let's look at the final frontier, where there's really no water at all. In fact, to transport water up to the International Space Station costs $15,000 a pint if we let the Russians do it, more if we send it up on Endeavor or Atlantis.
But today we got the marvelous news that instead of having to truck tons of water of space, the astronauts can just drink their own pee! (Yay?) Today marked a successful test of the International Space Station's water recycling system. The astronauts marked the occasion by raising a baggie (no glass in space) of recycled water (née urine) in a toast, and taking it a sip. They deemed it delicious, and, after taking a few questions from reporters, went about their day.
The system is actually surprisingly basic. Most of the water comes from the toilets, though dehumidifiers in the oxygen regeneration system remove three liters of water a day from the atmosphere. For the moment the atmospheric water is being hydrolyzed to provide oxygen for the workers, but eventually it will be put into the recycling system with everything else.
The wastewater goes through a seven-step filtration system. First, they strain out the solids. Yes, this includes poop, which is 75% water to begin with, and thus cannot be flung out with the trash. Then the water is boiled, and the steam trapped in a system that behaves remarkably like a still. As the steam runs through the pipes, it cools and condenses until it's pumped through a series of filters that are similar to water treatment down here on Earth. NASA says the water would pass muster in most municipal water systems.
In the end, though, they only recapture 93% of the water, no where close to the Fremen's skill. Of course, the actual stillsuit would have some pretty serious technical barriers to actually working, as detailed by NASA scientist John C. Smith in his stillsuit chapter of The Science of Dune (edited by SciNoFi pal Kevin Grazier). Among other problems, it would be unpleasantly warm, especially after a day in the desert; the human body doesn't provide enough kinetic energy to power the thing as author Frank Herbert suggested; and there would be great difficulties in cooling the evaporated water back into liquid. But, as Smith points out, Dune is set 13,000 years in the future. If today we can already make a unit the size of two-refrigerators for a space station, perhaps in 13 millenia we'll have a real, wearable stillsuit up and running.
Image courtesy of NASA
