Past innovations and future challenges
Space toilets
21ST CENTURY AND BEYOND
(Picture: James Blair/NASA)
The Universal Waste Management System was tested rigorously on Earth before being fitted to the ISS, where the mechanism is mostly hidden within a housing. It features separate elements to collect and process different types of waste. A funnel, removed and disinfected after use, is attached to this hose before astronauts use it for urinating; the liquid is pre-treated then filtered and recycled for drinking or other purposes – important for long stays on the ISS, and for other extended space missions during which the water supply can’t be topped up.
(Picture: James Blair/NASA)
The brown ring on the top of this unit is the seat. Though it might not look too comfortable, it’s the optimal shape to maximise contact for human bottoms; as with the urine hose, a vacuum pump ensures that solid waste doesn’t escape into the cabin. Handles and foot straps help the astronaut stay in place during use. The container beneath is lined with a waterproof bag to receive faeces; this is compacted, then typically placed in a canister that is jettisoned and burns up on re-entry into the Earth’s atmosphere. At present, water is not recovered from faeces for recycling and further use, but such a system may be implemented by NASA in future.
The problem of containing human waste in minimal or zero gravity has proven a challenge during long-haul space flights. In 1969, during the Apollo 10 mission around the Moon, astronaut Tom Stafford was heard to exclaim: “Give me a napkin, quick – there’s a turd floating through the air.” Since then, a variety of suction toilets have been used on space flights and in space stations – the model below was installed in the ISS Tranquility Module.
(Picture: NASA)
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Vacuum toilets employing some of the same principles are increasingly used in locations where water is scarce and flushing toilets would be impractical, or simply in an attempt to reduce water wastage. Those installed in settlements in Germany require only 1 litre of water per use – not to flush waste but to clean the bowl. The waste is then fermented in a biogas digester to produce methane for use in the community.