September 6, 2012
NASA Taking A Tip From Mother Nature To Process Waste In Future Spacecraft
Lee Rannals for redOrbit.com — Your Universe Online
A new concept driven by NASA could see that future spacecraft are more efficient when it comes to astronauts relieving themselves.The design, called Water Walls, would be able to help process waste on a spaceship, all while protecting astronauts from radiation.
Astronauts can thank mother nature for this design, because NASA said the Water Walls take an analogous approach to providing a life support system that is biologically and chemically passive.
Nature has a different way of doing things here on Earth than NASA does out in the International Space Station. On Earth, nature doesn't use compressors, evaporators, lithium hydroxide canisters, oxygen candles, or urine processors.
NASA said these electro-mechanical systems tend to be failure prone over time because the continuous use of them.
"Nature´s passive systems operate using biological and chemical processes that do not depend upon machines and provide sufficient, redundant cells so that the failure of one or a few is not a problem," NASA said in a statement.
The approach uses mechanical systems to pump fluids like gray water from the source to the point of processing.
"The core processing technology of Water Walls is FORWARD OSMOSIS (FO)," NASA said in the statement. "Each cell of the WW system consists of a polyethylene bag or tank with one or more FO membranes to provide the chemical processing of waste."
The Water Walls provide four principal functions of processing cells in four different types, plus the common function of radiation shielding.
The system uses gray water processing for urine and wash water, black water processing for solid waste, air processing for CO2 removal and O2 revitalization, green algae to provide food growth, and the cells provide radiation protection.
The cells are physically similar in size and shape, so they can be physically integrated into the Water Wall system. Using this cellular and modular approach, the system is designed to be reliable by being massively redundant.
NASA said the replaceable cells and modules are installed in the structural matrix, and before the spacecraft leaves Earth, they are primed with water and starter ion solutions.
As one cell for each function is used up, it is turned off, while the next one is turned on by opening valves to admit the appropriate fluids.
The space agency said the future spaceship will be carrying backup Forward Osmosis bags, or membranes, so once the cells become exhausted the crews can then replace them with new units.
"WW (Water Walls) can replace much of the conventional mechanically-driven life support that is so failure-prone with a reliable system that also affords 'non-parasitic' radiation shielding and can grow basic protein and carbohydrates to sustain the crew over multi-year missions," NASA said in the statement.