Urine and Feces May Shield Space Stations, NASA Says
NASA hopes that simple bag filters that can treat liquid and solid waste could also double as radiation shielding in space habitats.
Bags of urine or feces may seem totally unrelated to the shields that protect the spaceships of "Star Trek" and "Star Wars," but that's what NASA has in mind as protection for future space stations against dangerous radiation or meteorites.
NASA's new idea for space pioneers to recycle their urine, wastewater and feces isn't as crude as it first sounds. Lightweight filtration bags embedded in the walls of inflatable space habitats could save on launch weight costs compared to the usual life support hardware, and create a more self-sustaining existence for humans in space.
So-called membrane technology already exists for treating liquid and solid waste, and could theoretically work for scrubbing contaminants from air. The current models use off-the-shelf materials, and utilize a "forward osmosis" technique that filters water based on the pressure difference between wastewater and saltwater.
"We have about 75 percent of [the technology]," said Michael Flynn, a life support engineer at NASA Ames Research Center. "The air section has not yet been tested, but most of it exists at least in parts in the literature."
Waste-treatment bags could first hold sterile water that acts as both radiation shielding and as a freshwater supply. As the water supply is used up, the bags would switch to treating wastewater, filter out the solids, and then become a permanent addition to the space habitat walls.
"Water is a very good shield for radiation protection," Flynn told InnovationNewsDaily. "You are going to have to bring water anyway, so why not use it for life-support and radiation shielding?"
The membrane filtering method can recover more than 90 percent of the original water from wastewater, according to tests. Dry solids filtered from urine can create a handy buffer against both radiation and meteorites striking the space habitat.
Another process could chemically transform indigestible fiber in human feces into a material that resembles an adobe brick wall. The same processing can also create carbon dioxide and methane gas for harvest, as well as water vapor.
Not all space habitats can provide the right mix of waste materials to make all these approaches cost-effective, Flynn explained. Short-term transit habitats typically don't waste water on washing or other ordinary aspects of human hygiene, and so the waste is mainly limited to urine.
But a long-term space outpost or base on the moon or Mars might include wastewater from showering or washing clothes and dishes.
Human habitation in space or on extraterrestrial planets will always require more resources than it creates, Flynn said. But he added that there's always room for improving the self-sustaining cycle as more humans venture forth into space.
"We will always consume more than we produce," Flynn said. "The theory of entropy and the second law of thermodynamics dictate this. The best we can hope for is to come close to closing the loops."
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