What is the biggest challenge facing humans as we prepare for the first manned missions to Mars? Solar and cosmic radiation? Bone and muscle atrophy? Growing food? How about washing? It’s weird but true, right now we don’t have a way to clean laundry in space.
In the microgravity environment of space, nearly every aspect of how we do our laundry here on Earth becomes a fatal single point of failure. All that rocky water, heat cycles, spinning mass, and even a buildup of static electricity, lint, or fumes can jeopardize the job or even cost lives. But it sure is just a matter of engineering, right? If other hygiene activities such as bathing are successfully adapted to life in a space, why not do laundry?
For shorter tasks only there is no need. The longest Apollo and shuttle missions generally took about two weeks, which you might know from experience that you can pack. Pulling all that laundry is still lighter and cheaper than bringing your washer and dryer with you, especially if you’re going to ship them into space at a cost of nearly $50,000 a kilogram.
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Every space station we’ve built so far orbits a few hundred miles above the Earth’s surface, so while missions can last up to a year, washing is just part of the resupply process. New clothes and new linens, rigorously laundered several times on the floor to remove lint, are released aboard the resupply mission. Used clothes and linens are subsequently packed into a resupply vessel which is then removed, disassembled from orbit, and burned when it re-enters Earth’s atmosphere. While this sterilizes clothes with unparalleled effectiveness, it also makes them impossible to wear again.
But for the trip to Mars, which takes six or seven months in microgravity with no chance of resupply, using current methods, each astronaut would require at least 35 kilograms (75 pounds) of laundry for each transit. Certainly to bypass Mars, we are reaching a point where cleaning laundry in microgravity, and recovering used air and water, is more efficient in terms of mass and energy than bringing hundreds of pounds of limited-use clothing per person on each mission.
One of the main strategies is to make the dressing somehow slower. Simple things like wearing the same clothes on alternating days help. Spacecraft environments are designed to maintain a comfortable temperature and humidity, reducing sweating. Clothes also tend in microgravity to float away from the skin, slowing the absorption of sweat and oils.
Pushing the envelope begins with experiments like NASA’s Intra-Joint Activity Wear Study and Advanced Apparel System (ACS), and JAXA’s J-Wear, which has effectively demonstrated that materials and antimicrobial treatments can make clothing last for weeks instead of days. The two main strategies are to include copper or silver oxide in the fabric, or immerse the fabric in antimicrobial compounds.
Another way to save mass is to find ways to use up dirty laundry. During the Mir program, Russian scientists designed a culture of bacteria that could digest astronauts’ underwear and produce methane for power or propulsion. Recently, ISS Expedition 6 Science Officer Don Pettit used folded soiled underwear instead of actual soil to design tomato and basil seed planters. Expedition Six also saw Commander Ken Powersox wash his shorts in a plastic bag. This has not become a common practice on the International Space Station.
Unexpectedly, less fluid options such as exposure to vacuum, UV and microwave exposure were found to be only half the work. While it does kill many bacteria, it may have difficulty penetrating biofilms and does not remove bacteria waste or physical residue – which is what causes the smell of used clothing.
Perhaps the first practical attempt at a microgravity washing machine was the Integrated Microgravity Compatible Washing System (AMCILS), developed by the UMPQUA research company in the 1980s. The washer and dryer combo relies in particular on jets of water to move clothes and microwaves to dry them. As of 2017, the prototype has completed zero parabola testing.
In 2021, six teams of summer interns at NASA’s Glenn Research Center spent a week designing a washing machine. The Best Overall Design award went to a team that used a central switch instead of a drum to soak and move their laundry. NASA has hinted that the program may grow in the coming years, taking in the scope of programs like the Human Exploration Rover Challenge.
In August of 2020, parties from NASA and Tide’s parent company Proctor and Gamble signed a Space Act Agreement to develop the use of low-toxic detergents in microgravity, compatible with the International Space Station’s water reclamation system. The result of the agreement is P&G Telescience’s Investigation of Detergent Experiments (PGTIDE), the most stringent space wash experiment to date tested in flight.
Jessica Zina, Tide Scientist at P&G, prepares a load of laundry that will be washed in Tide’s laundry detergent solution for P&G Telescience Investigation of Detergent Experiments (PGTIDE). The cleaner will be aboard the SpaceX CRS-24.
After signing a Space Act Agreement with NASA, Tide is developing a space-cleaning solution that will aid in planned space travel such as the Artemis Moon missions and a round trip to Mars.
Image courtesy of P&G.
The PGTIDE experience consists of three distinct efforts. Launched in December 2021, the Target 1 payload is a sample of the Tide Infiniti test cleaner. In the O-1 experiment, astronauts on the International Space Station produced a variety of stains on a variety of fabrics and tested the effectiveness of Tide Infinity at removing them. The experiment was repeated on the ground to adjust the effect of microgravity on the cleaner. Throughout this phase, scientists have monitored the stability of infinity through months of microgravity and high ambient radiation levels in space.
Target 2 payloads, including the Tide To Go Pens and Wipes and Tide Rescue Spray, were launched to the International Space Station in July of this year. The main O-2 experiment will have astronauts treat a sample batch of pre-dyed fabrics from Earth and a batch of fabrics they stained in flight. The dependent variable will be the stain removal effectiveness of unmodified To Go products in space over a period of several months.
Finally, NASA and Tide researchers might design a washer-dryer combo that uses an Infiniti cleaner with as little energy and water as possible. The washer-dryer was designed for use in the low-gravity environment of a Moon or Mars colony, so unfortunately we may still be years away from a true deep space wash.
Tide Infiniti and beyond
Visualize your favorite science fiction scene. It might be a great fight. Maybe it’s an impassioned speech that’s stuck in your mind for years. It may be a moment when you realize how deep the friendship between two personalities is. Now ask yourself, in this scene, are their socks clean?
Washing clothes in space isn’t as flashy as, say, a full-flow combustion engine. But it may prove just as important to go to Mars and beyond. Both techniques are basically ways to get more performance for less mass. And in space, dropping mass is the only way forward.
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