The key location in Frank Herbert’s Dune novels (and the films of the same name) is mostly desert, with extreme heat and an almost total absence of water – and the less said about the giant sandworms, the better. Inhabitants rely on ‘stillsuits’, which recycle water from sweat and urine, to sustain them in the parched environment.
Drinking purified moisture from the body is not just a fantasy invention, however – it could soon be reality for astronauts, thanks to a prototype urine collection and filtration system inspired by stillsuits.
Outside the safety of a space station, spacewalkers rely on their suits for oxygen and protection from the environment. Over the five to eight hours of a typical mission, they may also need to relieve themselves, which is often uncomfortable and unhygienic. It is also wasteful, as the water from urine is not recycled in current suits, unlike wastewater on the International Space Station.
The new system, designed by researchers from Cornell University in New York state, aims to change that.
Relieving discomfort
Astronauts have long complained about a lack of comfort and hygiene when using the maximum absorbency garment (Mag), NASA’s ‘waste management system’ that essentially works like a multi-layered adult nappy made of superabsorbent polymer.
“The Mag has reportedly leaked and caused health issues such as urinary tract infections and gastrointestinal distress. Additionally, astronauts currently have only one litre of water available in their in-suit drink bags. This is insufficient for the planned longer-lasting lunar spacewalks, which can last 10 hours, and even up to 24 hours in an emergency,” said Sofia Etlin, research staff member at Weill Cornell Medicine and Cornell University, first author of a study detailing the new suit.
The design includes a vacuum-based external catheter leading to a combined forward-reverse osmosis unit to provide a continuous supply of potable water, with multiple safety mechanisms to ensure astronaut wellbeing.
The urine collection device includes an undergarment made of multiple layers of flexible fabric. This connects to a collection cup of moulded silicone, with a different shape and size for women and men. The inner face of the collection cup is lined with polyester microfibre or a nylon-spandex blend, drawing urine away from the body.
An RFID tag linked to an absorbent hydrogel activates a vacuum pump when moisture is detected, sucking the urine into the filtration system. There, the urine is recycled with an efficiency of 87% through a two-step, integrated forward and reverse osmosis system. This uses a concentration gradient to remove water from the urine, as well as a pump to separate water from salt.
The purified water is then enriched in electrolytes and pumped into the in-suit drink bag, available for consumption. Collecting and purifying 500ml of urine should take only five minutes, the researchers claimed.
The system, which integrates control pumps, sensors, and a liquid-crystal display screen, is powered by a 20.5V battery with a capacity of 40 amp-hours. Its total size is 38x23x23cm and it weighs 8kg, which its developers said should be “sufficiently compact and light to be carried on the back of a spacesuit”.
Microgravity tests
The prototype was developed with one eye on upcoming NASA Artemis missions. A crew will orbit the Moon in 2025, followed a year later by a landing on its south pole. Crewed missions to Mars are expected in the early 2030s.
“Our system can be tested in simulated microgravity conditions, as microgravity is the primary space factor we must account for. These tests will ensure the system’s functionality and safety before it is deployed in actual space missions,” said Dr Christopher E Mason, the study’s lead author.
The work was published in Frontiers in Space Technologies.
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