Astronauts who go out into space have to relieve themselves inside their spacesuits. This practice is not only uncomfortable and unhygienic, but it is also wasteful because unlike the wastewater on board the International Space Station (ISS), the water contained in astronauts’ urine is not recycled.
One solution to these problems would be to create full-body suits, like those in the blockbuster Dune franchise, that absorb and purify water lost through sweating and urination, and recycle it into drinking water. This science fiction is now about to become reality, with a prototype urine collection and filtration system for space suits. The project, carried out by researchers at Cornell University, is published in The Frontiers of Space Technology.
“The design includes an external vacuum catheter leading to a combined forward and reverse osmosis unit, providing a continuous supply of potable water with multiple safety mechanisms to ensure the well-being of astronauts,” said Sofia Etlin, a research staff member at Weill Cornell Medicine and Cornell University, and first author of the study.
Designed for upcoming missions to the Moon and Mars
In 2025 and 2026, NASA is planning the Artemis II and III missions, which will orbit the Moon and land on its South Pole, respectively. These missions are expected to be followed by manned missions to Mars by the early 2030s. However, astronauts have long complained about the lack of comfort and hygiene of the existing Maximum Absorbency Garment (MAG) — NASA’s traditional spacesuit waste management system, which has been in use since the late 1970s and functions like a multi-layer adult diaper made of superabsorbent polymer.
“The MAG is believed to have leaked and caused health problems such as urinary tract infections and gastrointestinal disorders. Additionally, astronauts currently only have one liter of water available in their in-suit drink bags. This is insufficient for the planned, longer lunar spacewalks, which can last ten hours or even up to 24 hours in an emergency,” Etlin said.
The astronauts also requested that the time required to fill and degas beverage bags inside spacesuits be reduced in future spacesuits, and that a separate supply of caffeine-free energy drinks be added.
With all these goals in mind, Etlin and his colleagues designed a urine collection device, consisting of an undergarment made of several layers of flexible fabric. This is connected to a collection cup (differently shaped and sized for women and men) made of molded silicone, to fit around the genitals.
The inner side of the collection container is lined with polyester microfiber or a blend of nylon and elastane, to draw urine away from the body to the inner side of the container, from where it is sucked out by a vacuum pump. An RFID tag, bonded to an absorbent hydrogel, reacts to moisture, activating the pump.
High-tech backpack
Once collected, the urine is routed to the urine filtration system, where it is recycled with 87% efficiency through an integrated two-stage forward and reverse osmosis filtration system. This system uses a concentration gradient to remove water from the urine, as well as a pump to separate the water from the salt. The purified water is then enriched with electrolytes and pumped into the suit’s integrated drinking bag, once again available for consumption. Collecting and purifying 500 ml of urine takes just five minutes.
The system, which integrates control pumps, sensors and a liquid crystal display, is powered by a 20.5 V battery with a capacity of 40 ampere-hours. Its total size is 38 x 23 x 23 cm, for a weight of about eight kilograms: compact and light enough to be carried on the back of a space suit.
Now that the prototype is available, the new design can be tested in simulated conditions and then during real spacewalks.
“Our system can be tested in simulated microgravity conditions, as microgravity is the main space factor we need to consider. These tests will ensure the functionality and safety of the system before it is deployed on real space missions,” concluded Dr. Christopher E Mason, a professor at the same institute as Etlin and lead author of the study.
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