Managing bodily waste presents unique challenges for astronauts due to the absence of gravity in space. Unlike on Earth, where gravity naturally aids waste removal, space environments require specialized systems to prevent waste from floating freely and ensure hygiene. These systems are designed for both in-suit operations and within the spacecraft.
In-Suit Waste Management
Astronauts require specific solutions for waste management when inside their pressurized suits, especially during launch, re-entry, and Extravehicular Activities (EVAs), or spacewalks. These periods can last for several hours, with spacewalks extending up to seven, making onboard toilet access impossible.
For these situations, astronauts wear a Maximum Absorbency Garment (MAG), which functions like a high-tech adult diaper. The MAG absorbs both urine and feces, though solid waste management is typically avoided during spacewalks through careful mission planning. This garment incorporates superabsorbent polymers, like sodium polyacrylate, which absorb significant liquid, transforming it into a solidified gel and pulling moisture away from the skin. A single MAG can hold up to 2 liters of liquid and is intended for use for eight to ten hours. While it provides an immediate solution, the MAG is temporary, and prolonged use is not suitable for hygiene.
Onboard Waste Management
Inside the spacecraft, such as on the International Space Station (ISS), astronauts use a “space toilet” system known as the Waste and Hygiene Compartment (WHC) or the Universal Waste Management System (UWMS). These systems rely on airflow instead of gravity to manage waste. To prevent astronauts from floating away, the space toilet includes foot restraints and handholds.
For liquid waste, astronauts use a specially shaped funnel and hose. This funnel creates a seal to ensure urine is drawn into the system by airflow. Solid waste is managed using a toilet seat that also uses airflow to pull waste into collection bags. The latest UWMS models feature ergonomic designs to improve comfort and efficiency for both male and female astronauts, allowing simultaneous use of the funnel and seat.
Liquid waste recycling is a key aspect of onboard waste management. Urine and condensed humidity from the cabin air, including sweat and breath, are collected and processed by the Water Recovery System. This system includes a Urine Processor Assembly (UPA) that uses vacuum distillation to recover water from urine and a Brine Processor Assembly (BPA) to extract remaining water from concentrated urine brine. Through this filtration and purification process, the ISS achieves a water recovery rate of up to 98%, producing potable water often purer than municipal drinking water on Earth.
Hygiene and Disposal
Maintaining hygiene protocols is important in the confined environment of a spacecraft to prevent contamination and safeguard astronaut health. Without traditional showers, astronauts rely on sponge baths using limited water and special no-rinse soaps and shampoos. Handwashing is a regular practice, often performed with waterless cleansers or limited amounts of water.
Solid waste, including used wipes and toilet paper, is collected in individual bags, compacted, and stored in airtight containers. Unlike liquid waste, solid waste is not currently recycled on the ISS for water recovery. These filled containers are periodically loaded onto uncrewed resupply vehicles, such as the Progress spacecraft. These vehicles then deorbit and burn up upon re-entry into Earth’s atmosphere, preventing waste accumulation on the station and eliminating the need to return it to Earth.