From Backpacking to Space Trekking

Water -- it's essential for life. When future space explorers venture beyond low Earth orbit, their only water supply will be on board their spacecraft. During the final space shuttle flight, NASA scientists plan to have astronauts test in microgravity a new method for recycling "used" water.

The idea is to make a fortified drink that provides hydration and nutrients from all sources available aboard a spacecraft, such as wastewater and even urine. The method set for testing uses a process known as forward osmosis.

"Forward osmosis is the natural diffusion of water through a semi-permeable membrane," explains Michael Flynn, research scientist at NASA's Ames Research Center. "The membrane acts as a barrier that allows small molecules, such as water, to pass through while blocking larger molecules like salts, sugars, starches, proteins, viruses, bacteria and parasites."

The forward osmosis method already is used for earthbound applications, allowing water of unknown purity to be changed into drinkable water in six to eight hours using a bag containing two chambers separated by a membrane. The commercial technology aids in diverse settings, from outdoor sports like hiking, to the military, to natural disasters where water purification is essential for survival.

The membrane alone can work for most water, but a two-stage system is necessary when recycling urine. It must first be filtered using an activated carbon bed, which removes urea and alcohol that would pass through the membrane alone.

Scientists from NASA's Kennedy Space Center in Florida plan to test a space-adapted version of the bag aboard space shuttle Atlantis during the STS-135 mission this summer. The group at Kennedy, led by NASA Project Manager Spencer Woodward, will include in the shuttle's cargo six forward osmosis bag kits for the astronauts to test. The bags' manufacturer, Hydration Technology Innovations of Albany, Ore., made a few adaptations to their commercial product for spaceflight and the same membrane, but the bag was remanufactured out of plastic that doesn't 'off gas' or burn," says Woodward, explaining that the fittings were also changed to a quick- release version already used in space to make it easier for the astronauts to work with in weightlessness.

The testing will come toward the end of the STS-135 mission, after undocking from the International Space Station. A shuttle astronaut will inject a prepared mixture of a lower concentration liquid containing dye into the outer chamber of the apparatus, which will represent the "dirty" water. He will then inject a higher concentrated "draw" solution into the bag's inner chamber, repeating the process for a total of six bags.