NASA will test a water purification method for long-duration space exploration on STS-135. 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 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. To conclude the experiment, after five hours, the crew member will use sample syringes to connect to the inner chambers of each bag and remove 60 milliliters of the sample from each of the six bags and stow them for landing. Once the samples
are returned to Earth aboard Atlantis, Project Scientists from Kennedy's Space Life Sciences Lab will conduct post-flight analysis of the samples to see how well forward osmosis worked in microgravity.

Results could prove that the device can have several applications for NASA in addition to the spacesuits. It could serve as an emergency backup source for water aboard the International Space Station, provide hydration and nutrition during emergency return-to-Earth scenarios, as well as aid during future long-term space exploration.