NASA's Universal Waste Management System during preflight testing, 2019. Image: NASA
The least glamorous system
Between commercial stations, lunar programs and private missions, the number of people living and working off Earth at any moment is on track to pass a hundred within about twenty years. Every one of them will need to eat, sleep, wash and use a bathroom.
“Everyone wants to design the cupola. Nobody wants to own the toilet. But the toilet is the thing that decides whether a hundred people can actually live up there.”Former Chief Designer, SpaceX Dragon
The toilet rarely appears in mission renderings, and it is almost never the system a program is proud of. Yet it is one of the few pieces of hardware that every crew member uses every day, on every mission, with no backup plan they would want to rely on. When it fails, the whole mission notices.
What a space toilet has to do
On Earth, a toilet relies on gravity and a water supply. In orbit there is neither. A space toilet has to do several jobs at once, in a few cubic feet, for people of different body types, and keep doing them for years.
- 01Separate and capture. Airflow replaces gravity, pulling urine and solid waste away from the body and into separate containers.
- 02Recover water. On the International Space Station, urine is processed and recycled into drinking water, so the toilet is the first stage of the water supply.
- 03Control air. Odor, bacteria and moisture have to be contained in a sealed cabin that the crew cannot ventilate.
- 04Stay quiet and private. The toilet sits inside a small shared volume. Noise and lack of privacy affect sleep, morale and how the crew lives together.
- 05Fail safely. When something breaks, the crew has to repair it themselves, often with limited tools and spares, and with a backup that is far less pleasant.
Sixty years of the same idea
NASA contracted Collins Aerospace to develop an updated toilet for exploration missions, the Universal Waste Management System (UWMS). The goals were to cut mass and volume, to share one core design across spacecraft, and to make it easier for women to use.
The ISS unit of the Universal Waste Management System during electromagnetic testing before launch, December 2019. Image: NASA
The Orion unit was delivered in December 2019 and installed in the Artemis II vehicle in March 2021. The ISS unit launched in October 2020. By most measures it is the best toilet NASA has built.
It still rests on the same principle as its predecessors: airflow moves waste away from the body. Each generation has been smaller, lighter and easier to use. None has been a different idea.
A fault on the way to the Moon
Artemis II was the first mission to take the UWMS beyond low Earth orbit. Shortly after launch on April 1, the crew reported a blinking fault light on the toilet, and NASA said the toilet fan had jammed. Working with mission control, the crew restored it to normal operation.
The system is also loud enough that the crew wore ear protection while using it. The most advanced toilet NASA has flown failed on the first day of the first crewed lunar mission in more than fifty years, and four astronauts on their way to the Moon spent part of that day fixing it.
Earth from Orion's window after the Artemis II translunar injection burn, April 2026. Image: NASA / Reid Wiseman
Why it keeps coming back
It would be easy to blame the hardware. The engineers who built the UWMS solved hard problems, and the toilet they delivered is a real improvement. The failures keep returning for a different reason: the way space programs decide what to fly makes it very hard for a fundamentally new toilet to ever reach orbit.
Flight history beats new ideas
Every program manager is judged on whether the mission flies safely and on schedule. Hardware that has already flown carries a record, test data and a supply chain. A new design carries only promises. So each vehicle inherits a refined version of the last toilet, and with it the last toilet's weaknesses. We call this the heritage trap: the safest choice for any single mission is the reason the same problems return across decades of missions. Toilets and CO2 filters are the two clearest examples.
Everything is connected to it
A space toilet is the front end of the water supply, part of the air system and a source of noise in a cabin the size of a van. Urine becomes drinking water. Odor and moisture end up in the air the crew breathes. A redesign touches all of these at once, which turns a toilet project into a life support project, and life support projects are the slowest and most expensive kind.
It has no natural owner
Waste management falls between life support engineers, interior designers and crew health specialists. Each group touches it; none is responsible for rethinking it. Without an owner there is no budget line for a clean-sheet design, only for fixes when something breaks.
Failures are survivable, so they are tolerated
When a toilet fails on a short mission, the crew has backups, mission control has procedures, and everyone gets home. That resilience is good engineering, but it also means the cost of a bad toilet is paid in crew time, discomfort and morale rather than in mission loss. Costs like that are easy to accept one mission at a time.
A co-founder of Paragon Space Development Corporation has spent a career in environmental control and life support, the field where waste and water systems live. The former Chief Designer of SpaceX Dragon shaped a crew vehicle around the people inside it. Their combined view covers both halves of the problem: the systems that keep a crew alive, and the design that makes those systems livable. Both are needed to get out of the pattern.
What changes when people stay
On a short mission, a temperamental toilet is an inconvenience. On a station where people live for months, or a lunar base where the next resupply is weeks away, it becomes a question of health, hygiene, water supply and whether the mission can continue.
Commercial stations raise the stakes again. Their crews will include private astronauts and researchers with less training than career astronauts, and operators will compete on how livable their stations are. A toilet that only experts can coax through a fault is not a product a commercial station can sell.
What it would take
Breaking the pattern does not require a breakthrough in physics. It requires treating the toilet as a first-class design problem and giving new approaches a fair path to flight.
- 01Design from the body out. Start with how people of different sizes and sexes actually use the system, then design the hardware around them.
- 02Design the system, not the seat. Develop waste, water, air and noise control together, so improvements in one do not create problems in another.
- 03Test early and on the ground. Use analog habitats, parabolic flights and long-duration ground tests to build evidence before a new design competes for a slot on a mission.
- 04Build a record. Give new systems a documented history of performance, so programs can choose them on evidence rather than on heritage alone.
The toilet is where the gap between what spacecraft can do and what people need is easiest to see. Closing it is part of making space a place people can live, not just visit.