Not so long ago, pursuing hygiene to preserve health was a revolutionary idea. In the late 1800's, public health hero Florence Nightingale observed that under difficult circumstances, hard-working people sometimes "lose the feeling of what it is to be clean." To prevent and cure illness, she helped her patients maintain personal and environmental sanitation. Nowadays, we continue to strive to maintain hygiene for the sake of health and several other reasons — both here on Earth, and in space.

But keeping clean enough to stay healthy is often easier said than done. Hygiene in space, where water never falls from the sky or flows into the palm of your hand, is especially challenging. At the same time, it is critical to both astronaut and mission health. On the International Space Station (ISS), 2-3 hours of daily exercise is mandatory, and like Earth-based exercise, it can generate a lot of sweat. A single skin infection can stop a spacewalk, delaying repairs and costing millions, so practicing good hygiene is a must to protect the crew. However, soap bubbles made in microgravity can sail merrily away, affixing themselves to instrument panels, sensitive electronics and other random surfaces, causing their own problems.

In a place where right-side-up is relative, and even the smallest health issue can jeopardize a mission, what is the right way to keep clean? And can any of the solutions scientists developed help us here on Earth?

Spacebound Hand Hygiene

The right hygiene in space stuff turns out to be a bit like camping, a bit like being on a submarine and a lot like throwing your used clothes and dirty dishes out the window. For the moment, let's focus on the camping part.

During long treks, hygiene consists largely of hand-washing, dish-cleaning and removing visible dirt and sweat with wet rags. Hand-washing is especially important on the trail. Hikers may not have packed along their colds and flus, but they surely brought their GI tracts. And wherever your guts go, so do billions of bacteria capable of causing disease in the person who brought them — as well as fellow campers. Poor hand hygiene has been shown to be responsible for half or more of illnesses among long-distance hikers on the trail.

To prevent similar outbreaks on the ISS, astronauts grab a pouch of "No-Rinse Body Bath." Basically, it's powdered soap, waiting to be reconstituted. Add a bit of hot and cold water from the taps in the walls, shake to mix, then squeeze yourself one ball of ready-to-use soap. Grab it before it can land on the power converters, rub it over your hands, and dry on a nearby towel. (You did bring your towel, right?)

How Do Astronauts Shower in Space?

No-Rinse Body Bath can be employed to clean the whole body, though space programs have tried other full-body hygiene solutions. In the 1970s, the Skylab space station featured a shower that accordioned open, brought in water at one end with hoses and drew it out the other with a vacuum system. For this to work, the user had to strap their feet to one end. While the idea of strapping in for a shower after a 3-hour daily workout may sound appealing, there's just one problem: Water is sticky. On Earth, water routinely sticks to our foreheads, faces and armpits. We casually wipe it away or let it drip to the floor. In microgravity, wiping water off your nose with your hand means that you now have water on your hand. It will stay there to some significant degree until you wipe it on something else. That is, assuming that you can wipe it off. Globs of water have been known to collect in front of the eyes, noses and mouths of ast ronauts performing spacewalks, cutting off their ability to see, speak and breathe.

Thus, a shower — or in the case of Skylab, a shower curtain — full of water can quickly become a microgravity clean-up disaster. Wiping every last bit of water off your body and the curtain before it migrates into someone's career-making laser experiment renders the prospect of a head-to-toe free-floating shower slightly less appealing. For that reason, as well as the simplicity and effectiveness of it, sponge-baths with No-Rinse or special wipes are the favored solution. These types of baths have been used by travelers for years and continue to be used by maritime travelers in ports with little access to freshwater, including submarines, where space is at such a premium that people of all genders use the same bathing area. Like submarines, space in space is at a premium. The resulting lack of privacy increases the desire to bathe quickly, quietly, in a spare moment in an unused sleeping area, rather than setting up a folding shower where your crewmates might come cruising by.

Hair Care in Free Fall

While astronauts can clean their bodies using the No-Rinse method, hair requires a bit of extra care. Modern space-based hair hygiene is less about showering and rinsing and more about squirting and rubbing. Rinseless shampoo, similar to what is used to wash the hair of hospital patients laying in their beds, helps to save water, time and damage to the vehicle. Trimming hair and beards without hurling razor cuttings into eyes and the air ducts means using suction: employing a vacuum while in a vacuum for the sake of health, hygiene and, yes, style. As international icons whose images circulate world-wide, astronauts need to maintain appearances. So, even though launching 1 kilogram into orbit can cost between $1,500-$35,000, we keep them clean — for their health and humanity's pride in maintaining a fleet of well-cared-for humans in space.

Strap In

Showering when you are accelerating toward the center of the Earth at the same rate as the water is a categorically different experience. How people experience space is starting to change. It has already changed. "How do astronauts shower in space?" is a question we are continuing to ask as we look forward to more and more citizen-astronaut crews, space tourists and orbiting hotels full of people who likely want to enjoy their once-in-a-lifetime vacations in olfactory peace.

What hasn't changed is the need to maintain hygiene to maintain human health. Right now, on Earth, lack of consistent access to clean water results in more suffering and death than wars, insects and famine combined. The art and science of water conservation and water recycling that ISS crews have mastered over the last generation could save, without exaggeration, tens of millions of lives every year. While today's astronauts hurl used clothes and contaminated food wrappers toward the Earth to be burned on atmospheric re-entry, that, too, is changing. Tide is developing cleaning solutions for the ISS that needs little, if any, water. In a world and on a station where clean water, clean air, clean food and clean people are at a premium, developing and testing the long-term technology to limit water use to two gallons of water per day while maintaining health and happiness is revolutionary.

While here on Earth we've mastered the basics of hygiene and may take it for granted, astronauts have to keep it constantly in mind. Practicing good hygiene in space is a necessary step for protecting the whole mission.

Interested in all things in outer space and exploration? We are too. Take a look at open positions at Northrop Grumman and consider joining our team.