What To Wear, What To Wear...?
By Alan Dove, PhD, NYAS Contributor
As space agencies consider sending astronauts on voyages that could last months or years, ordinary activities that we take for granted on Earth become major scientific and engineering challenges. Consider that most mundane of all human chores: laundry.
Aboard the International Space Station, astronauts receive regular deliveries of fresh clothing from Earth. They typically wear each outfit for several days before throwing it into the trash, which is then “de-orbited” to burn up in Earth's atmosphere. That approach is clearly unsustainable. If future space crews want to reach more distant destinations, they'll need to move past incinerating their underwear.
Given the impracticality of planting acres of cotton on Mars or raising silkworms in microgravity, sustainable space clothing will require entirely new strategies for manufacturing and maintaining textiles. Fortunately, researchers working at the frontiers of fabric design are already exploring ideas that could make clothing more sustainable both in space and on Earth.
Many of the requirements for clothing a human body on Earth will be the same anywhere in the universe. “One of the most important things is thermal comfort, when the weather gets cold you want to keep yourself warm, and when the weather is hot, how do you cool yourself down?” says Yi Cui, Professor of Materials Science and Engineering at Stanford University. He adds that “we [also] need to get the sweat out.”
Cui and his colleagues have developed several types of textiles that can help with those challenges. In one project, the researchers created a nanoporous metallic coating that can be embedded into cloth, causing it to reflect infrared radiation back towards the body. Another effort yielded a nanoporous polyethylene textile that allows infrared radiation to escape.
The two technologies can be combined in a single garment. “This bifunctional textile has two layers of coating ... so you can wear it one way and this can keep your body warm, but if you wear it inside out ... then you can cool your body down.”
Widespread use of such garments could save significant amounts of energy, either aboard space stations or inside office buildings. “If you wear this in the indoor environment, then your air conditioning does not need to be so cool in the summer, and the set point can go up several degrees Celsius,” says Cui. His calculations show that this change alone could decrease building energy consumption by 30 percent in a warm climate.
For space exploration, bifunctional outfits could help astronauts to adapt to enormous temperature changes from day to night on planets with thin or nonexistent atmospheres.
Cui has also thought about the laundry problem. “Would you be able to wash your clothing? Probably you would not have that much water [in space],” says Cui. Instead, he envisions self-cleaning clothing, perhaps using nanoengineered antibacterial coatings to inhibit odors and continuously sanitize the cloth.
Keeping an antibacterial coating active might require energy, but that could also come from the clothing itself. Cui explains that future textiles may incorporate photovoltaic systems to generate their own power supply from available light. Alternatively, an outfit could exploit the temperature difference between the body and the environment to generate power, an approach that could work especially well when the garment is designed to cool the wearer. Instead of simply letting the excess heat escape, a power-generating garment would redirect it to generate electricity.
Harvesting energy from clothing is a high priority for textile engineers, as they already have plenty of ideas that will require power. “Sensing body condition could become important, and ... textiles could even do therapeutics, deliver drugs and things like that,” says Cui. Clothing that senses and responds intelligently to the wearer's condition and the environment would help long-distance space travelers cope with extreme conditions, while likely finding clinical uses on the ground as well.
Space outfits loaded with smart sensors, personal climate control, and energy collecting circuitry could have one major drawback, however: maintenance. When these complex systems inevitably break down, they'll need to be fixed or rebuilt without support from Earth. Cui points out that the cooling fabric he developed, at least, is recyclable. Astronauts could theoretically melt it, extrude fresh fibers, and weave them into a new garment to replace the old one.
Score one for the cows
Other textile developers agree that recyclability will be critical for sustainable space travel. “You can't have things shipped to you, you need to be working with some sort of system ... using your own waste stream as an input for anything that you need to consume,” says Suzanne Lee, Chief Creative Officer for Modern Meadow and founder of the Biofabricate Conference in New York City.
Modern Meadow's approach to sustainability draws on the original closed-loop recycling system: biology. The company's first product is a biofabricated leather produced by microbial fermentation. “We actually start with collagen, which is the protein that makes up a material like leather, but we have it in a liquid form, and then we can do endless things with that protein in that form,” says Lee.
While the notion of omitting animals from leatherworking may appeal to vegans, Lee explains that the benefits of biosynthesis extend much further. Fermentation can be scaled to use far fewer resources than animal farming, and genetically engineered microbes can make collagen from a wide range of potential feed stocks, including waste that might be produced on a space voyage.
Biofabrication also shortens the path to the final product. Rather than being constrained by the shape and thickness of an animal hide, Modern Meadow's leather can be sprayed, extruded and molded in whatever ways product developers need. “You're also able to form it potentially around a three-dimensional form, so then you get into reducing the numbers of processes that you might have in manufacturing, [negating] the need for a piece of equipment like a sewing machine,” says Lee.
Spiderman was on to something
While biofabrication could help produce a sustainable supply of ordinary clothing for astronauts, Lee cautions against trying to apply it too broadly. “Let's not underestimate the complexity of materials for space,” she says. For example, a space suit for extra-vehicular use is likely too complex to consider growing from scratch. Instead, multi-layered garments and spacecraft components with sophisticated life-support roles would likely be repaired rather than recycled on a long voyage.
That said, at least some of the components of future space fabrics may come from biofabrication. Lee points to spider silk, the strongest natural fiber, which several research teams and companies are now trying to manufacture at commercial scale. Clothing and even structures may soon incorporate spider silk, taking advantage of its extraordinary strength-to-weight ratio combined with its relatively low environmental impact.
Rather than pure spider silk bridge cables or textiles, Lee sees this and other biofabricated fibers being combined with more conventional materials. “You might want the functionality of a biofabricated material, but combine it with an existing yarn or an existing textile structure,” says Lee.
None of the new bio-materials have achieved the manufacturing scale needed to meet demands on Earth, and making these processes portable enough for space travel will require even more development. However, the field has produced some promising prototypes. AMSilk, a Germany-based producer of silk biopolymers, collaborated with sportswear giant Adidas recently to produce a biodegradable athletic shoe. Another company, Bolt Threads of Emeryville, CA, produced a pilot batch of leather-like hats made with fungal mycelium.
Whether future astronauts actually end up recycling their clothing or growing new pairs of socks from their garbage, thinking about the constraints of space travel gives researchers a framework for improving sustainability closer to home. “It's an environment where you're really trying to get the most out of the smallest amount of resources you have,” says Lee, adding that “as we think about a more populous Earth, then I'm sure it will have applications here too.”
It might even be the demise of the weekly laundry chore as we know it.