On earth, gravity draws wastes into the toilet and pulls the water down when we flush. Because of the lack of gravity in space, NASA engineers had to design a new type of toilet that uses a vacuum. Flowing air instead of water moves waste through the system.

The WMS (Waste Management System) was originally developed for the Space Shuttle Orbiter in 1981. It collects liquid and solid waste products from crew members and stores the wastes separate from the crew in a safe, odorless form. Since 1981, the missions have become longer and the number of crew members has increased. NASA engineers have made many improvements to the design of the WMS.

The WMS has two major components: a urine funnel and a commode system.

Urine Funnel:

Air draws the urine into the funnel and it is transported to the fan/pump separator where liquid is separated in a rotating bowl and pumped into the wastewater storage tank. Wastewater is vented to space, where it vaporizes.

Commode System:

Air draws solid wastes into the commode tank. Solid wastes are dried, compressed, stored on-board, and then removed after landing. Up to two compactions of the waste material take place during an eighteen-day mission.

Crew members must use foot restraints, thigh restraints, and handholds to prevent them from floating away while they are using the WMS. The air used in both the urine funnel and commode systems is filtered to remove odor and bacteria and then returned to the cabin.

Source:
 •Hubert Brasseaux, NASA Environmental Control and Life Support Systems Engineer