| Fact | Value and condition | Planning use |
|---|---|---|
| ISS water recycling | About 90% of water-based liquids, including urine and sweat, as stated by NASA astronaut Jessica Meir in 2020 | Cuts the supplemental water that must be launched from Earth |
| Mars-mission recycling goal | 98% recycling rate targeted before the first human missions aboard a proposed Mars transport vehicle | Sets the bar that deep-space life support has to clear |
| Round-trip Mars mission | About two years, with no opportunities to top off the water supply | Rules out relying on resupply or on venting water away |
| Universal Waste Management System (UWMS) | 65% smaller and 40% lighter than the current space station toilet | Saves volume and mass on crewed vehicles |
| Short-mission waste | Not pre-treated with chemicals and simply stored for disposal | Fits brief flights where water recovery is not needed |
These figures come from NASA’s feature on its new space toilet.
How do astronauts go to the bathroom in space? They use toilets that pull urine and feces away from the body with airflow, because gravity cannot do the job, and on the International Space Station most of the urine is recycled into water.
The way waste is handled sets how much water a crew must carry, which is why it counts as part of the technology needed for a mars base and for the trip there, not just a hygiene detail.
Why waste handling is a life support decision
On the International Space Station (ISS), the toilet is the front end of the water system. NASA says the station’s regenerative life support system is critical to reducing the need to launch supplemental water. That system is part of the Environmental Control and Life Support System (ECLSS), and the toilet feeds it.
The consequence is that the right toilet design depends on mission length and on whether water can be resupplied. Three situations call for different choices.
- Low Earth orbit with regular cargo flights. The ISS recycles about 90% of its water-based liquids, according to NASA astronaut Jessica Meir. Recycling pays off here because every litre recovered is a litre that does not have to be launched.
- Short trips beyond low Earth orbit. On brief flights the cheaper option is to store waste or vent wastewater overboard. NASA notes that on a short mission waste is not pre-treated with chemicals and is simply stored for disposal. Recycling hardware adds complexity that a trip of days does not repay.
- Mars transit. NASA says round-trip Mars missions will take about two years, with no opportunities to top off the water supply. NASA’s goal is therefore to reach 98% recycling rates before the first human missions aboard a proposed Mars transport vehicle. The gap between about 90% and 98% looks small, but it decides how much water must be stored for a journey with no resupply.
Distance is what removes the resupply option. The How Far Is Mars From Earth? Distances, Why They Change, and What It Means for Travel (2026) – Decolonizemars guide explains how far a Mars-bound crew would be from Earth. How long the trip takes also depends on propulsion, a subject covered in How Fast Do Rockets Go? Real Speeds, Missions, and What Limits Them (2026 Guide) – Decolonizemars.
A sensible reading of these facts is that a toilet is judged by how well it feeds the water loop and how little it adds to mass and volume. Comfort and reliability matter too, but they come second to that test.
What happens to urine and solid waste
Urine and solid waste follow separate routes in orbit, and only one of them is recovered.
Urine and water recovery
Urine is mostly water, more than 90% according to The Conversation’s explainer on space bathrooms, which also reports that all astronaut urine is collected and turned back into clean, drinkable water. So the answer to whether urine is recycled into drinking water on the ISS is yes. NASA’s wider figure, about 90% of all water-based liquids including urine and sweat, shows the recycling covers more than urine alone.
On long missions, NASA says the UWMS will feed pre-treated urine into a regenerative system, which recycles water for further use. Pre-treatment is what lets the recovered liquid enter the water loop reliably, and short flights skip it because they do not recycle.
Solid waste and disposal
Solid waste is not recycled. According to The Conversation, it is vacuumed into garbage bags, which are then placed in airtight containers, with wipes and gloves used for cleaning. The containers are loaded onto a resupply cargo ship, which burns up in Earth’s upper atmosphere. Most bathroom waste is therefore removed from the station by incineration on re-entry.
This puts a practical limit on the approach. It works when cargo vehicles visit regularly and are destined to burn up on return. A vehicle on a two-year Mars trip has no such disposal route, so solid waste there would have to be stored. The material does not make the trip lighter, which is one reason water recovery gets most of the design attention.
How the toilet works in microgravity
Without gravity, nothing falls, so the toilet moves waste with moving air. NASA states that space toilets use air flow to pull urine and feces away from the body into receptacles.
- A funnel and hose for urine. The user holds a specially shaped funnel and hose tightly against the skin so that nothing leaks out, as The Conversation describes it. Airflow does the pulling, so a good seal matters more than position.
- A seat for bowel movements. The seat is separate from the funnel. NASA says the funnel and seat can be used simultaneously, reflecting feedback from female astronauts.
- Handholds and footholds. The bathroom is full of them so that astronauts do not drift off. Staying anchored matters because the airflow only works when the user stays in contact with the funnel or seat.
This layout suits crews of mixed bodies and habits better than one shared fixture would. It also explains why the hardware looks more like a piece of plumbing than a chair.
The UWMS and Orion
The Universal Waste Management System is NASA’s newer toilet design. NASA says its build is 65% smaller and 40% lighter than the current space station toilet. A UWMS unit launched to the ISS on the 14th Northrop Grumman resupply mission in September 2020. A second unit was installed in the Orion spacecraft for the Artemis II flight test, a 10-day mission beyond the Moon and back.
That second installation shows the design moving from the station toward deep space. Orion is a short-trip vehicle, so it uses the toilet differently from the ISS. Houston Public Media reported that on Artemis II the wastewater was vented overboard daily, rather than being fed to a recycling system. This matches NASA’s point that short missions skip chemical pre-treatment and store waste for disposal.
The Artemis II crew’s verdict on the hardware was positive. The mission’s commander, Reid Wiseman, said, “The toilet worked great.” The same design supplies two kinds of benefit. On the ISS it supports a water-recycling loop, and in Orion it provides a compact toilet for a short trip. For Mars, a design would have to deliver the recycling benefit on a vehicle with no cargo link, which is why the 98% goal matters.
Frequently asked questions
How is odor controlled in the toilet?
Airflow does it. NASA says a new feature of the UWMS is the automatic start of air flow when the toilet lid is lifted, which helps with odor control.
What happened when the Artemis II toilet had a problem?
Houston Public Media reported a suspected ice blockage in the toilet’s vent on April 4. The crew was instructed to use collapsible contingency urine devices at that point.
How much do the UWMS toilets cost?
Houston Public Media reports that NASA developed two UWMS toilets, which cost as much as $23 million. That figure covers the two units NASA developed, not a price per seat for future vehicles.
Is there a NASA video that shows how the station toilet is used?
Yes. NASA+ published a video on how to use the bathroom in space on November 3, 2023, featuring astronaut Chris Cassidy. NASA introduces it as an answer to one of the most frequent questions about life on the station.
