NASA Science News
November 2, 2000
Rationing and recycling will be an essential part of life on the newly-populated International Space Station. In this article, the first of a series about the challenges of living in orbit, Science@NASA explores where the crew will get their water and how they will (re)use it.
Interesting quote from the attached reference: Without such careful recycling 40,000 pounds per year of water from Earth
would be required to resupply a minimum of four crew members for the life of the station. Interesting data. Using the fact
that there is 8.33 lb. of water/gallon then the 40,000 lb/year for 4 crew members becomes 40,000/(8.33*4) = 1200 gal/year
per person or 1200/365 = 3.4 gal/person per day. Other interesting and applicable statements: Once on board the ISS,
spacefarers are in for a steady diet of sponge baths using water distilled from -- among other places -- their crewmates
breath!... If you're an astronaut, you'll wet the wash cloth with a spray nozzle and then use the cloth to wash your
hands. On the space station, people will wash their hands with less than one-tenth the water that people typically use on
Earth. Instead of consuming 50 liters to take a shower, which is typical on Earth, denizens of the ISS will use less than
4 liters to bathe.
Comments on the data presented: Using the conversion factor 1 liter = .264 gal, then on earth about 13.2 gal is used for a shower. In space about 1 gallon is used to bathe. Now to try and get a minimum usage of quality water/day per person after the pole shift, lets look at a what-if scenario. Lets say most people drink less than a gallon/day. Lets also say we use one more gallon for washing vegetable and cooking. Lets take a sponge bath once a week this is 1/7 gal/day. Now suppose we wash our hands using a wash cloth 3 times/day say this takes about 3/7 gal/day. This gives a total of about 2.5 gal/day of quality water needed. This assumes we wash our cloth and boots in lower quality of water.
Bottom line: We will need about 2.5 to 3.5 gallons per day for each person of quality water to live safely yet comfortably. If we assume we use a lower quality of water for pre-washing vegetables and washing cloths then I think as a bare minimum if absolutely necessary the water one drank would need to be of quality, and all else could be a lower quality of water. For example the lower quality water could be filtered for small particles, Ozone purified, and carbon filtered. The quality water could include the above but also be run through a reverse osmosis filter or distillation process. Distilled water could come from dehumidifiers, refrigerator drip pan, still tents, or commercially available distillation units. A third type of water would be unfiltered and could be used for washing some things like boots etc. What we feed to our plants would depend on how much of what type water we have. I see three or more grades of water in common use.
Offered by Mike.