Spacesuit filter system makes body fluid drinkable

A research team at Cornell University has tackled the problem of astronauts not being able to carry enough water in their spacesuits on long space missions. The researchers have developed a spacesuit with a filter system that can make urine drinkable. This kills two birds with one stone, as it also solves a hygiene problem.

The first author of the study, Sofia Etlin, was inspired to carry out the project by reading the "Dune" novels by Frank Herbert. In it, the author describes a "stillsuit" that can constantly collect sweat and urine and convert it into drinking water so that people can survive on the water-poor planet "Dune". In the study "Enhanced astronaut hygiene and mission efficiency: a novel approach to in-suit waste management and water recovery in spacewalks", published in Frontiers in Space Technologies, the scientists describe their approach to processing urine into drinking water.

Water shortage and hygiene problem

NASA currently uses maximum absorbency garments (MAG) in its spacesuits to soak up urine. The diaper-like MAGs develop their absorbency from several layers. However, MAGs can leak and, in the worst case, cause urinary tract infections and gastrointestinal irritation. This could pose a particular problem for long-term space missions, such as those planned for the Artemis moon missions. In addition to the hygiene problem, the astronauts only carry a limited supply of water and could therefore suffer from a lack of water. So far, the 1-liter drinking bags used are only sufficient for spacewalks of less than ten hours. The newer Axiom spacesuits for Artemis missions are designed to hold two liters, which is still too little.

The scientists at Cornell University opted for a pragmatic approach and concentrated on processing urine to obtain drinkable water. For this purpose, a sex-specific collection cup that encloses the genitals collects the urine. It contains a soft, absorbent material consisting of polyester microfiber and a nylon/spandex blend. This is intended to promote moisture absorption and better direct the urine away from the body to the inside of the container. A moisture sensor detects as soon as urine is excreted and automatically switches on a vacuum pump, which extracts the liquid and forwards it to a two-stage filter system.

Conversion into drinking water

Converting the urine into drinking water, on the other hand, was a greater challenge, says Etlin. The researchers investigated several different methods, such as reverse osmosis, filtration by bacteria, the use of electrolysis and the use of space radiation. After evaluation, the scientists opted for a combination of forward and reverse osmosis. This process promised a high level of water purity with low-energy consumption.

The combined process initially involves forward osmosis. The urine passes through a special filter membrane, which extracts clean water from a salt-like solution. During reverse osmosis, another filter removes all remaining impurities. As a result, only drinking water remains, according to the researchers. The water consists of around 99 percent pure water and contains only a few traces of salts.

The process developed by the scientists works quickly and efficiently: 500 ml of urine can be converted into water in just five minutes. The amount of water produced in this way could keep the astronauts hydrated during longer outdoor missions, the researchers promise.

The system, which weighs around eight kilograms and fits into a rucksack, is not yet suitable for future space suits. The system still has to be tested under zero gravity conditions, among other things, to guarantee its functionality.

(olb)