<P> A space toilet, or zero gravity toilet, is a toilet that can be used in a weightless environment . In the absence of weight, the collection and retention of liquid and solid waste is directed by use of air flow . Since the air used to direct the waste is returned to the cabin, it is filtered beforehand to control odor and cleanse bacteria . In older systems, waste water is vented into space, and any solids are compressed and stored for removal upon landing . More modern systems expose solid waste to vacuum pressures to kill bacteria, which prevents odor problems and kills pathogens . </P> <P> When humans travel into space, the absence of gravity causes fluids to distribute uniformly around their bodies . Their kidneys detect the fluid movement and a physiological reaction causes the humans to need to relieve themselves within two hours of departure from Earth . As a result, the space toilet has been the first device activated on shuttle flights, after astronauts unbuckle themselves . </P> <P> There are four basic parts in a space toilet: the liquid waste vacuum tube, the vacuum chamber, the waste storage drawers, and the solid waste collection bags . The liquid waste vacuum tube is a 2 to 3 - foot (0.91 m) long rubber or plastic hose that is attached to the vacuum chamber and connected to a fan that provides suction . At the end of the tube there is a detachable urine receptacle, which come in different versions for male and female astronauts . The male urine receptacle is a plastic funnel two to three inches in width and about four inches deep . A male astronaut urinates directly into the funnel from a distance of two or three inches away . The female funnel is oval and is two inches by four inches wide at the rim . Near the funnel's rim are small holes or slits that allow air movement to prevent excessive suction . The vacuum chamber is a cylinder about 1 - foot (0.30 m) deep and six inches wide with clips on the rim where waste collection bags may be attached and a fan that provides suction . Urine is pumped into and stored in waste storage drawers . Solid waste is stored in a detachable bag made of a special fabric that lets gas (but not liquid or solid) escape, a feature that allows the fan at the back of the vacuum chamber to pull the waste into the bag . When the astronaut is finished, he or she then twists the bag and places it in a waste storage drawer . Samples of urine and solid waste are frozen and taken to Earth for testing . </P> <P> The toilet used on the Space Shuttle is called the Waste Collection System (WCS). In addition to air flow, it also uses rotating fans to distribute solid waste for in - flight storage . Solid waste is distributed in a cylindrical container which is then exposed to vacuum to dry the waste . Liquid waste is vented to space . During STS - 46, one of the fans malfunctioned, and crew member Claude Nicollier was required to perform in - flight maintenance (IFM). An earlier, complete failure, on the eight - day STS - 3 test flight, forced its two - man crew (Jack Lousma and Gordon Fullerton) to use a fecal containment device (FCD) for waste elimination and disposal . </P>

Where does the poop go in a space shuttle