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Zero gravity looks cool. But what about the thing no one likes to talk about? Yes, that is right: going to bathroom. Zero gravity makes this everyday task quite a challenge. Astronauts have to be toilet-trained all over again.

The Apollo astronauts raised themselves off the seat of their chairs and stuck a clear plastic bag to their back sides with sticky strips. A second astronaut watched closely to be sure no waste matter escaped the seal. (You would not want that stuff floating around the cabin!) When the deed was done, the astronaut cleaned up with a piece of plastic attached to the inside of the bag, removed the bag, dropped a disinfectant pill in with the waste matter, and put the whole thing, sealed, into a special container.

Donald W. Rethke, an engineer for Hamilton Standard Space Systems, developed a more private way to answer nature’s call: the space toilet. It is somewhat like the kind of toilet one would find on commercial airplanes --- with unique adaptations for zero gravity, of course. For instance, it has thigh bars that keep the astronaut from floating off the seat.

The astronaut (male or female) defecates (排便) in a bag and urinates (排尿) in a hose. Solid and liquid wastes are kept separated because at least 85% of the urine is recycled and, yes, after careful filtration, used for drinking and other purposes. (Water is always in demand in space.) A vacuum sucks the waste materials into the toilet, where the waste is compacted into hamburger-like patties for easy storage. Although not exactly like an earthbound visit to the toilet, it is at the very least much more private than in the early days of space travel.