Recycling Water is not Just for Earth Anymore
Nature’s been recycling water on Earth for eons, and now NASA is set to do the same thing above Earth on the International Space Station.
Space shuttle Endeavour is carrying two refrigerator-sized racks packed with a distiller and an assortment of filters designed to process astronauts’ urine and sweat into clean drinking water.
The station crew depends now on water carried up aboard a space shuttle or cargo rocket. But an operational water recycler is expected to cut that need by 65 percent by producing about 6,000 pounds of potable water each year. That’s enough fresh water to allow the station to host six crew members instead of three.
A system that operates on the station also will provide a significant stepping stone to developing even more efficient processes that will support astronauts on the moon or on long-duration voyages into the solar system.
Although Russia’s space station Mir recycled cosmonaut’s sweat, the NASA recycler is the first to be flown in space that intends to cleanse and reuse almost all the water a crew member produces.
The system can recycle about 93 percent of the water it receives, said Bob Bagdigian, the Environmental Control Life Support System project manager at NASA’s Marshall Space Flight Center in Huntsville, Ala.
The water recycler counts in large part on a distiller that Bagdigian compares to a keg tilted on its side. On Earth, distilling is a simple process of simply boiling water and cooling the steam back into pure water. But without gravity, the contaminants in water never separate from the steam no matter how much heat is used.
“In space, it becomes quite a challenge to distill any liquid in the absence of gravity,” Bagdigian said.
So the keg-sized distiller is spun up to produce an artificial gravity field. The contaminants in the urine press against the sides of the drum while the steam gathers in the middle and is pumped to a filter.
The filters are not much different from those used on Earth, which means they use charcoal-like materials to pull more unwanted elements from the water. Another process uses chemical compounds that bond with the remaining contaminants so filters can pick them out of the water, too.
“The water that we produce meets or exceeds most municipal water product standards,” Bagdigian said.
The system has been in different stages of development ever since NASA committed to building a space station in the 1980s. Along the way, individual parts of the system have been flown on space shuttle missions for tests.
The distiller mechanism flew in 2003 and worked just fine in orbit, Bagdigian said.
Now the crew of the International Space Station will test the whole apparatus, but they won’t drink any at first. Instead, they will take numerous samples and return them to Earth for detailed testing. After the testing is complete, controllers will clear the astronauts to use the fresh water in orbit.
NASA’s water filter development has also helped produce filters that are now used in humanitarian efforts to make clean water in areas served only by contaminated sources.
The effort to make a crew support system that reduces the need for fresh supplies from Earth includes an oxygen generator that is already installed in NASA’s Destiny lab on the space station.
Housed in one rack instead of the two required for the water recycler, the oxygen producer splits the oxygen and hydrogen molecules in water and sends the oxygen into the space station as breathable air. The hydrogen is now dumped overboard. However, another process is under development that will combine the hydrogen with other chemicals that react with each other and produce more water.
While the water recycler in use will work fine for the International Space Station’s needs, Bagdigian said work is already under way to make it more efficient so it can be used on long moon exploration missions.
“We’ll take this system and continue to push its performance and efficiency,” Bagdigian said.
NASA's John F. Kennedy Space Center