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Sci-fi Life Support

Oct. 30, 2006: In Frank Herbert's epic ecological novel Dune (1965), set 
on the fictitious desert planet Arrakis in another star system, water is 
so precious that even perspiration and breath moisture are captured and 
purified for drinking.

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.

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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.

Stepping-stone to the stars. Regenerative ECLSS will get a field test 
onboard the ISS

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).

ECLSS hardwareThe 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.

ECLSS in Iraq--Since April 2006, an Earth-bound application of a portion 
of the ECLSS water recovery system has been being trucked from one rural 
village to another in northern Iraq to filter particulates and 
contaminants out of dirty groundwater or well water to provide residents 
with clean drinking water. That portable system—about half the size of a 
refrigerator including all its pumps and computer controls—purifies 
water at a good clip of 4 gallons a minute, for a cost of only about two 
cents a gallon.

Technical details of ECLSS appear in "Status of the Regenerative ECLSS 
Water Recovery and Oxygen Generation Systems" by Robert M. Bagdigian, 
Dale Cloud, and John Bedard (Paper 2006-01-2057) and in NASA Facts 
"International Space Station Environmental Control and Life Support 
System" (Pub 8-40399, May 2005).

ECLSS fact sheet

The Vision for Space Exploration
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