When a space-walking astronaut needs to relieve themselves they often have to do so in adult-style nappies inside their spacesuits. This is not only uncomfortable and unhygienic, but also wasteful too.

Researchers at Cornell University have now created a prototype urine collection and filtration system that allows astronauts to recycle their urine into, er, drinkable water (Frontiers in Space Technology doi:10.3389/frspt.2024.1391200).

The system can collect and purify about 500 ml of urine in five minutes. The urine is first collected via a collection cup made from moulded silicone that is lined with a nylon-spandex blend before being vacuum pumped to the urine filtration system where 87% of the liquid is recycled.

The purified water is then mixed with electrolytes and pumped into a drinks bag where it can be consumed.

“Astronauts currently have only one litre of water available in their in-suit drink bags,” notes Cornell’s Sofia Etlin. “This is insufficient for the planned, longer-lasting lunar spacewalks, which can last ten hours, and even up to 24 hours in an emergency.”

Yet at eight kilograms and the size of a backpack, it might need some miniaturization before it can be used by prospective Mars colonizers.