The Fremen who inhabit the harsh desert world of Arrakis in Frank Herbert's Dune must rely on full-body "stillsuits" for their survival, which recycle absorbed sweat and urine into potable water. Now science fiction is on the verge of becoming science fact: Researchers from Cornell University have designed a prototype stillsuit for astronauts that will recycle their urine into potable water during spacewalks, according to a new paper published in the journal Frontiers in Space Technologies.
Herbert provided specific details about the stillsuit's design when planetologist Liet Kynes explained the technology to Duke Leto Atreides I:
It's basically a micro-sandwich—a high-efficiency filter and heat-exchange system. The skin-contact layer's porous. Perspiration passes through it, having cooled the body ... near-normal evaporation process. The next two layers ... include heat exchange filaments and salt precipitators. Salt's reclaimed. Motions of the body, especially breathing and some osmotic action provide the pumping force. Reclaimed water circulates to catchpockets from which you draw it through this tube in the clip at your neck... Urine and feces are processed in the thigh pads. In the open desert, you wear this filter across your face, this tube in the nostrils with these plugs to ensure a tight fit. Breathe in through the mouth filter, out through the nose tube. With a Fremen suit in good working order, you won't lose more than a thimbleful of moisture a day...
The Illustrated Dune Encyclopedia interpreted the stillsuit as something akin to a hazmat suit, without the full face covering. In David Lynch's 1984 film, Dune, the stillsuits were organic and very form-fitting compared to the book description, almost like a second skin. The stillsuits in Denis Villeneuve's most recent film adaptations (Dune Part 1 and Part 2) tried to hew more closely to the source material, with "micro-sandwiches" of acrylic fibers and porous cottons and embedded tubes for better flexibility.
The Cornell team is not the first to try to build a practical stillsuit. Hacksmith Industries did a "one day build" of a stillsuit just last month, having previously tackled Thor's Stormbreaker ax, Captain America's electromagnetic shield, and a plasma-powered lightsaber, among other projects. The Hacksmith team dispensed with the icky urine and feces recycling aspects and focused on recycling sweat and moisture from breath.
Their version consists of a waterproof baggy suit (switched out for a more form-fitting bunny suit in the final version) with a battery-powered heat exchanger in the back. Any humidity condenses on the suit's surface and drips into a bottle attached to a CamelBak bladder. There's a filter mask attached to a tube that allows the wearer to breathe in filtered air, but it's one way; the exhaled air is redirected to the condenser so the water content can be harvested into the CamelBak bladder and then sent back to the mask so the user can drink it. It's not even close to achieving Herbert's stated thimbleful a day in terms of efficiency since it mostly recycles moisture from sweat on the wearer's back. But it worked.
Suited for space
Astronauts on board the International Space Station (ISS) have made some 269 spacewalks since the ISS launched in 1998, usually lasting around six hours, with the longest being nearly nine hours. The ISS has a water treatment system for recycling wastewater, capable of recycling as much as 98 percent of all the water used by astronauts on board, although the membranes used can become fouled and contaminated over time. However, astronauts must relieve themselves inside their spacesuits during spacewalks, and that waste is not recycled. They wear a disposable adult diaper to collect urine and feces, technically called a Maximum Absorbency Garment (MAG) on spacewalks, and an In-suit Drink Bag (IDB) provides drinkable water.
For NASA's planned Artemis II and III missions, a crew will orbit the moon and land on its south pole in preparation for planned manned missions to Mars in the 2030s. Those missions will require much longer lunar spacewalks—hence the focus on finding novel solutions. Astronauts have historically loathed wearing the MAG, often limiting how much food they eat before spacewalks to avoid doing so, which reduces their work efficiency during physically demanding spacewalks as well as not being good for their health. Astronauts would also prefer not to spend as much time filling and de-gassing the IDBs.
"The MAG has reportedly leaked and caused health issues such as urinary tract infections and gastrointestinal distress," said co-author Sofia Etlin, a researcher at Weill Cornell Medicine/Cornell University. "Additionally, astronauts currently have only one liter 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.” So Etlin and her co-authors set about designing a prototype system inspired by Herbert's stillsuits.
In the new system, the MAG has been replaced with a urine collection device (UCD) that collects urine via an external catheter soon after it is expelled from the body, containing feces separately to avoid any cross-contamination. This UCD is made of multiple layers of flexible fabric and connects to a collection cup of molded silicone designed to fit around the genitalia. There are different shapes and sizes for male and female astronauts. The cup is lined with polyester microfiber designed to draw the urine away from the body.
A vacuum pump at the cup's inner face then draws the urine away and delivers it to the urine filtration system (UFS). The pump is activated via an RFID tag linked to an absorbent hydrogel that reacts to moisture. The filtration system combines forward and reverse osmosis to remove contaminants from urine with 87 percent efficiency, filtering it into potable water. Electrolytes are then added to the recycled water via a flavored powder and pumped into the IDB for consumption. The whole process takes about five minutes per 500 ml of urine.
The system weighs about 8 kg (17.6 pounds) and can be worn as a backpack. "We believe that the increased comfort and resource efficiency provided by the system will more than make up for the slightly increased bulk," the authors wrote. The next step will be to test the prototype in simulated microgravity conditions to ensure it is both functional and safe, followed by testing during actual spacewalks.
Frontiers in Space Technologies, 2024. DOI: 10.3389/frspt.2024.1391200 (About DOIs).
