How do astronauts poop?

On Earth, the flush and gravity do all the work. In orbit, they must be replaced by an airflow: a fan continuously sucks air through the bowl and funnel, so that everything leaving the body is carried in the right direction without escaping into the cabin.

The rest is a matter of technique. Crew members strap in or brace their feet to avoid drifting, aim precisely at an opening a few centimeters wide, then seal it carefully. Crews practice on the ground on a mockup fitted with a camera, since the maneuver depends on a positioning that nothing on board corrects naturally.

Solid waste falls into a disposable bag, which is sealed and packed into a container. These containers are then loaded onto a resupply cargo ship emptied of its freight, which burns up over the ocean during reentry into the atmosphere.

Urine, on the other hand, is valuable. It goes into a processing system that distills and purifies it along with cabin humidity condensate, before it is reintroduced into drinking water. Recycling on board avoids having to launch every liter from the ground, at a prohibitive launch cost; crews joke about it when toasting with yesterday's coffee.

Early flights made do with bags stuck to the skin, a messy and dreaded operation that Apollo crews described bluntly. The shuttle and then the station brought real toilets, at first bulky and finicky. A more compact generation, designed for use by both women and men, joined the station in the early 2020s and serves as a test bed for future lunar spacecraft.