On real-life voyages to the Moon and Mars, science fact may end up imitating science fiction. Indeed, scientists and engineers at NASA's Marshall Space Flight Center (MSFC) are putting the finishing touches on systems for capturing exhaled carbon dioxide and urine and turning them into breathable oxygen and drinking water.
"Early space missions—Mercury, Gemini, Apollo—took with them all the water and oxygen they needed and discarded liquid and gaseous wastes into space," explains Robert Bagdigian of the MSFC. In short, the astronauts' life-support systems were "open-loop"—meaning they relied on resupply from Earth, something still true for the International Space Station, today.
But for any long-duration missions to the Moon or Mars, "it makes sense to close the loop"—that is, to recycle air and waste water instead of just discarding them. Soon the ISS will be testing just such a regenerative system.
The name of the project is Environmental Control and Life Support Systems--better known by its acronym ECLSS (pronounced"EE-cliss"). Bagdigian is the ECLSS project manager.
"The Russians are ahead of us," says Robyn Carrasquillo, engineering manager for ECLSS. "The original Salyut and Mir spacecraft were able to condense humidity right out of the air and use electrolysis—an electric current run through the water—to produce oxygen for breathing." NASA's new regenerative ECLSS, to be launched to ISS in 2008, goes further: "it can recover urine in addition to humidity."
Urine recovery is an engineering challenge: "Urine is so much dirtier than ordinary humidity," Carrasquillo explains. "It can corrode hardware and clog hoses." ECLSS uses a purification process called vapor compression distillation: urine is boiled until the water in it turns to steam. The steam—essentially clean water vapor except for some traces of ammonia and other gases—rises into a distillation chamber, leaving behind a concentrated brown soup of impurities and salts that Carrasquillo charitably calls "brine" (which is discarded). The steam is cooled and condenses back into liquid. This steam distillate is then mixed with the humidity condensate, and the water further purified to become potable. ECLSS can recover 100 percent of moisture in the air, and 85 percent of the water in urine, resulting in a net overall recovery efficiency of about 93 percent.
That's how it works on Earth. In space, there's an additional challenge: "steam doesn't rise." Buoyancy requires gravity, and in the microgravity of a spaceship, steam just "sits there." It doesn't rise naturally into the distillation chamber. So in the version of ECLSS being completed at Marshall for ISS, "we spin the entire distillation system to create artificial gravity to separate the steam from the brine," says Carrasquillo.
Moreover, in microgravity human hairs, skin cells, lint, and other impurities float around in the air instead of falling to the floor. Thus, the processor requires an impressive filtration system. When clean water emerges at the end, iodine is added to retard the growth of microbes (chlorine, used to purify water on Earth, is too reactive and hazardous to store and handle in space).
The regenerative water recovery system for ISS, weighing about a ton and a half, will "produce half a gallon an hour, more than the current of crew three needs," Carrasquillo says. "This will enable the space station to support a total of six astronauts continuously." The system is designed to produce potable water "meeting purity standards better than most municipal water systems on the ground," Bagdigian adds.
In addition to providing drinking water for the crew, the water recovery system will supply water to the other half of ECLSS: the oxygen generation system (OGS). The OGS operates by electrolysis. It splits water molecules into oxygen for breathing and hydrogen, which is vented outside the spacecraft. "The air loop needs pretty clean water, so the electrolyte cells don't get contaminated and foul," Bagdigian points out.
"Regeneration is far more cost-effective than resupplying the station with water from Earth," Carrasquillo says, especially after the space shuttle is retired in 2010.
Recycling up to 93 percent wastewater is impressive. But for missions of months or years to the Moon or Mars, some later version of ECLSS must achieve closer to 100 percent efficiency.
Then, astronauts would be ready to survive on our own solar system's versions of
Dune.
Source: Science@NASA, by Trudy E. Bell
Related stories:
New Water Reclamation System Headed for Duty on Space Station
International Space Station crews soon will have a new water reclamation system that will recycle wastewater, allowing up to six crew members to live aboard the orbiting laboratory.
Mars Odyssey Shifting Orbit for Extended Mission
(PhysOrg.com) -- The longest-serving of six spacecraft now studying Mars is up to new tricks for a third two-year extension of its mission to examine the most Earthlike of known foreign planets.
ASU Mars instrument gets new lease on life as NASA extends Mars Odyssey mission
A six-minute rocket firing on Sept. 30 has put NASA's Mars Odyssey spacecraft on track for a new orbit around the Red Planet. The change, part of a two-year extension for the mission, will give an ASU-operated instrument carried on Odyssey greater sensitivity for mapping Martian minerals. The instrument is the Thermal Emission Imaging System (THEMIS), a multi-band heat-sensing camera operated by ASU's Mars Space Flight Facility.
Liquid Mirror Telescopes on the Moon
A team of internationally renowned astronomers and opticians may have found a way to make "unbelievably large" telescopes on the Moon.
Deep biosphere research points to new methods for recovering petroleum
Miles below us, deep within Earth's crust, life is astir. Organisms there are not the large creatures typically envisioned when thinking of life. Instead, thriving there are microbes, the smallest and oldest form of life on Earth. Although the biological diversity of these deep biosphere microorganisms may surpass that of the more familiar surface biosphere, much about them is still unknown, including the origin of the organic compounds they consume. Arizona State University researchers are using a novel approach that integrates physical organic chemistry with organic geochemistry and biogeochemistry to uncover the source of these organic compounds.
Cassini flyby of Saturn moon offers insight into solar system history
NASA's Cassini spacecraft is scheduled to fly within 16 miles of Saturn's moon Enceladus on Oct. 9 and measure molecules in its space environment that could give insight into the history of the solar system.
NASA study finds rising Arctic storm activity sways sea ice, climate
A new NASA study shows that the rising frequency and intensity of arctic storms over the last half century, attributed to progressively warmer waters, directly provoked acceleration of the rate of arctic sea ice drift, long considered by scientists as a bellwether of climate change.
NASA Selects Science Teams for Astrobiology Institute
(PhysOrg.com) -- NASA has awarded five-year grants, averaging $7 million each, to 10 research teams from across the country, including two from NASA's Jet Propulsion Laboratory in Pasadena, to study the origins, evolution, distribution and future of life in the universe.
