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 airflow. 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, wastewater 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. Background Astronauts say that they are most often asked how they go to the bathroom in space. In space, weightlessness causes fluids to distribute uniformly around human bodies. Kidneys detect the fluid movement and a physiological reaction causes the humans to need to relieve themselves within two hours of departure from Earth. The space toilet was thus the first device activated on shuttle flights, after astronauts unbuckled themselves. Mechanism In the absence of gravity, space toilets use air flow to pull urine and feces away from the body and into the proper receptacles. A new feature of the space toilet is the automatic start of air flow when the toilet lid is lifted, which also helps with odor control. By popular (astronaut) demand, it also includes a more ergonomic design requiring less clean-up and maintenance time, with corrosion-resistant, durable parts to reduce the likelihood of maintenance outside of the set schedule. Less time spent on plumbing means more time for the crew to spend on science and other high-priority exploration focused tasks. The crew use a specially shaped funnel and hose for urine and the seat for bowel movements. The funnel and seat can be used simultaneously, reflecting feedback from female astronauts. The space toilet seat may look uncomfortably small and pointy, but in microgravity, it is ideal. It provides ideal body contact to make sure that everything goes where it should. The space toilet includes foot restraints and handholds for astronauts to keep themselves from floating away. Everyone positions themselves differently while “going”, and consistent astronaut feedback indicated that the traditional thigh straps were a hassle. Toilet paper, wipes, and gloves are disposed of in water-tight bags. Solid waste in individual water-tight bags is compacted in a removable fecal storage canister. A small number of fecal canisters are returned to Earth