Giant leaps for water reuse in space
Water is crucial for astronauts to live and work in space, whether orbiting the Earth, working at a lunar base or travelling to Mars. At four NASA centres scientific engineers are developing dependable ways of recycling water for space travel and possible Earth use. Natasha Wiseman reports.
Engineers have designed the next-generation water recycler to run for years without maintenance. A preliminary engineering development unit can recycle 3.785L/h of wastewater into drinkable water.
"If we were going to Mars tomorrow, this is the water treatment system that astronauts might well use," explained Michael Flynn, a scientist at NASA's Ames Research Center in California, who is developing the recycler in cooperation with a private company, Water Reuse Technology. "This unit can enable a six-person crew to shower, wash clothes and dishes, drink water and flush toilets over three years without water re-supply," Flynn explained.Engineers say the development of reliable water recycling for space exploration is a very important factor in reducing spacecraft launch weight and, consequently, cutting costs.
"Water accounts for 87% of the supplies that astronauts need to keep alive," Flynn said. "If you want to reduce the cost of sending people to Mars, the water recycler is one way to do it."
The water recycler is being developed on a timeline to fit into NASA's exploration plans, according to Flynn.
"Basically, tests have to be done on the unit to flight qualify it - to make sure materials do not emit harmful fumes, and to investigate other potential microgravity operation problems," he explained.
The engineering development unit includes two box-shaped components about 1m x 1.4m called the Vapor Phase Catalytic Ammonia Removal (VPCAR) system designed specifically for a Mars transit spacecraft.
The system uses a process called vacuum-vapour compression distillation. During distillation, lightweight organic compounds in the water are removed by a catalytic method that uses platinum on aluminium pellets and operates at about 250oC. Another catalytic bed, which operates at about 450oC, converts any nitric oxide produced in the first bed into nitrogen and oxygen gas.
The high temperatures in the catalytic beds also sterilize any biologically active fluids or vapours, according to scientists. During tests, the system regularly recovered 98% of the water in a wastewater stream that contained urine, humidity condensate and hygiene waste and purified this wastewater into potable water.
Next, NASA will test VPCAR in a human test facility.
Engineers at NASA's Johnson Space Center (JSC) in Texas are working on technology to minimise the size of biological water processors for space habitats. JSC microbiologist Leticia Vega is developing modular biological processors that can be easily removed and cleaned.
Researchers are also identifying soaps that rapidly degrade at high concentrations. Researchers are studying ways of optimizing the size of ion exchange beds used for the final purification of water.
A combined life support system to support a seven-member crew on the International Space Station (ISS) is being developed by engineers at Hamilton Sundstrand Space Systems International in Connecticut and researchers at NASA's Marshall Space Flight Center (MSFC) in Alabama.
Scheduled for delivery in 2008, the new systems should cut annual delivered water to the ISS by more than 6 million m3.
The Water Processor Assembly (WPA) will be the first major hardware delivery of the Regenerative Environmental Control Life Support System. Together, the WPA and the Urine Processor Assembly make up the Water Recovery System which feeds the Oxygen Generation System.
"The Water Processing Assembly can produce over 132,475m3 of potable recycled water daily," said project manager Bob Bagdigian.
The WPA is scheduled for delivery in 2008.
Currently, ISS crewmembers are allocated about 2L daily, they stretch the ration by collecting, cleaning and reusing wastewater, airborne condensation and urine.
Chemical and microbial contaminants are a health risk in space, just as on Earth, they also risk clogging complicated fluid systems. The Aerobic Rotational Membrane System research project at NASA's Kennedy Space Center (KSC) in Florida may help. "We're trying to move toward a biological treatment method using bacteria to help cleanse the water," said Tony Rector, Dynamac Corporation's bioprocess engineer at KSC.
Many of these recycling technologies may have Earth-based uses. NASA is working with the Expeditionary Unit Water Purification Program of the US Office of Naval Research and Bureau of Reclamation to explore ways to use this recycling technology in remote locations.
Contact: NASA Ames Research Center
Tel: +1 650 604 5026