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To Boldly Go: The Science Behind Pooping in Space

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What Mike Mullane remembers most clearly about having his first bowel movement in space is the blast of cold air greeting his exposed rectum. Over the course of three week-long NASA shuttle missions in the 1980s—two for Discovery, one for Atlantis—Mullane was forced to answer nature's call six or seven times in zero gravity. Each time, he would have to strip naked, close a flimsy curtain around a titanium commode, position his buttocks to form a perfect seal around a 4-inch opening, and then follow a checklist posted nearby to make sure no fecal particles escaped into the deck—all while his sphincter insisted on clamping shut to escape the freezing temperatures.

"It was a complex operation," Mullane tells Mental Floss. "On Earth, I'm fast. My wife is amazed I can be in and out of the bathroom in one minute for a number two. On the shuttle, it would take 30."

While the industrial toilet was a far cry from five-star hotel room seat warmers and bidets, it also improved by magnitudes the ordeal of emptying one's intestines in zero gravity. Prior to 1972, the men of the Gemini and Apollo missions braved poop bags that they would stick to their rear ends, then manually knead the contents with an antibacterial solution so the gases wouldn't detonate the collection; more than one crew has been terrorized by rogue turds hovering in the air.

Coming up with a practical way of replicating the earthbound poop experience took many years, many engineers, and a whole lot of ingenuity. While few explorers like to discuss it, taking a space dump is its own kind of heroism.

Consider one early—and discarded—solution for waste collection in space, which someone dubbed the "sh*t mitt." Donald Rethke likens it to "those long rubber gloves veterinarians use for insemination." The idea, he tells Mental Floss, was that the astronaut could poop in their own hand and then turn the glove inside-out, creating instant containment of the feces.

Now 80, Rethke is a retired engineer from Hamilton-Standard, a NASA subcontractor working through Northrop Grumman that spent decades refining or pioneering life-support systems for space explorers. Rethke, who embraces his industry nickname of "Doctor Flush," says that handling poop simply wasn't much of a concern due to the brief trips taken by pioneering astronauts: They could just go before they left. But as missions grew longer, it became necessary to address personal waste—urine and bowel movements—without dealing with the discomfort of diapers.

A NASA training commode
A training toilet with a camera positioned inside so astronauts can learn how to best angle their buttocks.
National Geographic, YouTube

For the 1965–66 Gemini excursions, which were planned to prove humans could survive for several days or weeks in space, astronauts were told to use a condom-like sheath that would direct urine into a bag. For feces, they were to use a pouch with a 1.5-inch opening and an adhesive strip around the edge to help prevent fecal matter from escaping. A fellow crew member would be told to stand by and watch to make sure no waste escaped into the capsule.

"It kind of looked like an upside-down top hat," Mullane says. Though they pre-dated his missions, they were on board his shuttles in case of equipment failure. "We never had to use them, thank God."

But the occupants of Gemini and Apollo did, and most found it unpleasant for reasons unrelated to crapping in a bag. When gravity is lacking, surface tension becomes a dominant force. So urine and feces that would separate from the body on Earth thanks to gravity tend to cling to the skin's surface in space.

"If you stick your finger into a glass of water and lift it up, water flows off," Mullane explains. "But in weightlessness, the attraction of the molecules of the fluid will pull it into a ball. If you leave fluid alone, it will form a perfect sphere. Touch it, and will stick to you."

The same goes for poop. The bags had tiny finger covers built in so users could flick and scrape errant flecks away from their cheeks. Then they'd mix in a chemical to kill the bacteria so the gases wouldn't expand in the sealed bag and create an explosive biohazard.

"Well, it's in a small, like a ketchup, a little plastic container like you find ketchup in in restaurants, in a cafeteria or something, it's like that," Apollo astronaut Russell Sweickhart told a reporter in 1977. "You tear the slit across the top, being careful not to squeeze it so the stuff comes out, and then you drop that into the fecal container, and then seal the fecal container. Then you squeeze it through the, you know, externally, you know, which forces it out of the container, and then you mix it by massaging the fecal bag. It's really fun when it's still warm."

If everything went well, it was merely disgusting. If it didn't, as the following transcript excerpt from the 1969 Apollo 10 mission demonstrates, it could be highly disruptive:

Tom Stafford: Give me a napkin quick. There's a turd floating through the air.

John Young: I didn't do it. It ain't one of mine.

Gene Cernan: I don't think it's one of mine.

Stafford: Mine was a little more sticky than that. Throw that away.

Young: God Almighty.

"When the Apollo astronauts came back," Rethke says, "they wanted sit-down toilets."

A look at the ISS bathroom
The "orbital outhouse" inside the International Space Station.
NASA

While modesty may not have been an achievable goal, astronauts needed some semblance of routine. (Some shuttles were equipped with kitchen tables, even though nothing in zero gravity could be perched on one.) But the comforts of a domestic commode had little application in space. No water could be used: It would run everywhere. And unlike gravity-assisted toilets, a shuttle john would have to address the surface tension issue that enticed poop to come out in curls instead of straight down, mashing itself against the skin.

The solution, according to Rethke, was gentle suction. "Or, as I like to call it, air entrainment," he says. In its simplest form, it's getting the poop Hoovered away from your bottom using air flow as a substitute for gravity.

Rethke says the idea was already on the table courtesy of General Electric (GE) when Hamilton-Standard began working on a zero gravity toilet, and that his job was one of refinement that lasted through the 1980s and 1990s. "The concept of separating solids from the body was already in the bag, no pun intended. It was just the best way. Most of my effort was how to do that economically."

NASA had previously toyed with a variety of designs, including one 1971 model that was mounted vertically on a wall to conserve space. Another took the feces and pulped it, a model not unlike evacuating into a blender. This, engineers realized, created the potential for fecal "dust," or powdered particles of poop, that could contaminate the cabin of spacecraft. By using air entrainment, hardly anything could escape the bowl—and if it did, it wouldn't be atomized to the point of being a biological hazard. Instead, a fan and vacuum system was used to encourage the waste to settle at the bottom of the waste tube.

Air entrainment made one frustrating demand of its users: proper anal positioning. With a 4-inch opening compared to a conventional toilet's 18 inches, astronauts had to align themselves up perfectly in order to avoid any escaping feces. To train astronauts heading for space, NASA set up a commode with a camera mounted inside. (You were not expected to make a deposit.) Users could gauge their perch based on freckles or other skin marks in relation to the seat. Properly docked, they could poop on target, but it took practice.

"It's hard to know where your a-hole is when the hole is that narrow," Mullane says.

Minor complaints aside, NASA's work was ready in time for the 1973 debut of Skylab, the first space station, and the 1981 launch of Columbia, the first shuttle to reach space. After realizing the pulverizing model wasn't going to work due to the fecal dust issue and other malfunctions that led to problems on 10 of the shuttle's first 11 voyages, a redesigned system less prone to clogging was introduced in the mid-1980s.

Urinating, according to Mullane, was never any big deal. Men and women use a form-fitting cup and gentle suction to empty their bladder. "Pretty simple," he says. "But solid waste, that was kind of like going in a camper toilet."

On the Atlantis and Discovery, the space commode had foot rests and thigh straps so astronauts could remain secure to the seat while doing their business. They'd typically opt to strip naked in the event any soiling occurred. To the right was a hand lever; pushed forward, it slid open the tube underneath their buttocks. "You never wanted to open that before sitting on it," Mullane says. Doing so could release the previous user's residual fecal matter into the air.

Once Mullane was strapped in, he would open the tube cover and feel the rush of cold air hit his rear. The air moved 360 degrees while a fan underneath—loud enough to mask sounds of elimination—pulled waste away from the body and into a container that would store the matter until the shuttle returned. Toilet paper would go in a separate bag. By the time Mullane got dressed, cleaned the toilet's edges, and exited, 30 minutes had passed.

Surprisingly, the intimate size of the shuttle didn't contribute to any fragrant evidence. "They did a really good job of filtration," Mullane says. "You never smelled anything."

Rethke improved on this in the early 1990s by compacting the discarded feces at the bottom, reducing the need for storage space. (To make sure it would stay sealed, Rethke once kept a feces-filled container in his office for a year.)

Small tweaks aside, the space toilet doesn't follow the update schedule of, say, an iPhone. What Rethke redesigned and what Mullane used is, by and large, what's still in use on the International Space Station (ISS) today. But instead of bringing waste back, it's discarded so it burns up in the atmosphere.

Future movements may prove more difficult to handle. With the advent of long-duration travel, possibly to Mars, on the horizon, space exploration will have to deal with the issue of waste management when there's virtually no chance of Earthbound assistance.

"When toilets fail [on Earth], it's a real pain," Mullane says. "Just imagine that on Mars. I have no idea how they're going to do that."

Someone might. In early 2017, the HeroX platform crowned a winner in its Space Poop Challenge, which crowdsourced ways to handle waste in space when an explorer is in a spacesuit and away from a fixed toilet for long periods. The winning idea—a suit hatch that can be used to insert inflatable bedpans and diapers—earned inventor Thatcher Cardon a $15,000 prize. If it works, it'll assist in an integral part of exploring beyond our atmospheric borders. In space, everyone needs to go.

Additional Sources: Riding Rockets: The Outrageous Tales of a Space Shuttle Astronaut

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Big Questions
Does Einstein's Theory of Relativity Imply That Interstellar Space Travel is Impossible?
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Does Einstein's theory of relativity imply that interstellar space travel is impossible?

Paul Mainwood:

The opposite. It makes interstellar travel possible—or at least possible within human lifetimes.

The reason is acceleration. Humans are fairly puny creatures, and we can’t stand much acceleration. Impose much more than 1 g of acceleration onto a human for an extended period of time, and we will experience all kinds of health problems. (Impose much more than 10 g and these health problems will include immediate unconsciousness and a rapid death.)

To travel anywhere significant, we need to accelerate up to your travel speed, and then decelerate again at the other end. If we’re limited to, say, 1.5 g for extended periods, then in a non-relativistic, Newtonian world, this gives us a major problem: Everyone’s going to die before we get there. The only way of getting the time down is to apply stronger accelerations, so we need to send robots, or at least something much tougher than we delicate bags of mostly water.

But relativity helps a lot. As soon as we get anywhere near the speed of light, then the local time on the spaceship dilates, and we can get to places in much less (spaceship) time than it would take in a Newtonian universe. (Or, looking at it from the point of view of someone on the spaceship: they will see the distances contract as they accelerate up to near light-speed—the effect is the same, they will get there quicker.)

Here’s a quick table I knocked together on the assumption that we can’t accelerate any faster than 1.5 g. We accelerate up at that rate for half the journey, and then decelerate at the same rate in the second half to stop just beside wherever we are visiting.

You can see that to get to destinations much beyond 50 light years away, we are receiving massive advantages from relativity. And beyond 1000 light years, it’s only thanks to relativistic effects that we’re getting there within a human lifetime.

Indeed, if we continue the table, we’ll find that we can get across the entire visible universe (47 billion light-years or so) within a human lifetime (28 years or so) by exploiting relativistic effects.

So, by using relativity, it seems we can get anywhere we like!

Well ... not quite.

Two problems.

First, the effect is only available to the travelers. The Earth times will be much much longer. (Rough rule to obtain the Earth-time for a return journey [is to] double the number of light years in the table and add 0.25 to get the time in years). So if they return, they will find many thousand years have elapsed on earth: their families will live and die without them. So, even we did send explorers, we on Earth would never find out what they had discovered. Though perhaps for some explorers, even this would be a positive: “Take a trip to Betelgeuse! For only an 18 year round-trip, you get an interstellar adventure and a bonus: time-travel to 1300 years in the Earth’s future!”

Second, a more immediate and practical problem: The amount of energy it takes to accelerate something up to the relativistic speeds we are using here is—quite literally—astronomical. Taking the journey to the Crab Nebula as an example, we’d need to provide about 7 x 1020 J of kinetic energy per kilogram of spaceship to get up to the top speed we’re using.

That is a lot. But it’s available: the Sun puts out 3X1026 W, so in theory, you’d only need a few seconds of Solar output (plus a Dyson Sphere) to collect enough energy to get a reasonably sized ship up to that speed. This also assumes you can transfer this energy to the ship without increasing its mass: e.g., via a laser anchored to a large planet or star; if our ship needs to carry its chemical or matter/anti-matter fuel and accelerate that too, then you run into the “tyranny of the rocket equation” and we’re lost. Many orders of magnitude more fuel will be needed.

But I’m just going to airily treat all that as an engineering issue (albeit one far beyond anything we can attack with currently imaginable technology). Assuming we can get our spaceships up to those speeds, we can see how relativity helps interstellar travel. Counter-intuitive, but true.

This post originally appeared on Quora. Click here to view.

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Space
Astronauts on the ISS to Teach Christa McAuliffe's Lost Science Lessons
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Christa McAuliffe was set to become the first private citizen to travel to space when she boarded the Challenger space shuttle on January 28, 1986. That dream was cut tragically short when the shuttle exploded 73 seconds after liftoff, killing all seven passengers onboard. Now, 32 years later, part of McAuliffe's mission will finally be realized. As SFGate reports, two NASA astronauts are teaching her lost science lessons in space.

Before she was selected to join the Challenger crew, McAuliffe taught social studies at a Concord, New Hampshire high school. Her astronaut status was awarded as part of NASA's Teacher in Space Project, a program designed to inspire student interest in math, science, and space exploration. McAuliffe was chosen out of an applicant pool of more than 11,000.

Once in orbit, McAuliffe had planned to conduct live and taped lessons in microgravity for her students and the world to see. Though that never happened, she left behind enough notes and practice videos for astronauts to carry through with her legacy 32 years later. On Friday, January 19, astronaut Joe Acaba announced that he and his colleague Ricky Arnold will be sharing her lessons from the International Space Station over the upcoming months. The news was shared during a TV linkup with students at Framingham State University where McAuliffe studied.

McAuliffe's lost lesson plan includes experiments with Newton's laws of motion, bubbles, chromatography, and liquids in space, all of which will be recorded by Acaba and Arnold and shared online through the Challenger Center, a nonprofit promoting space science education.

It will be the first time students will get to see the lessons performed in space, but it won't be the only footage of the lessons available on the internet. Before the doomed Challenger flight, McAuliffe was able to practice her experiments in NASA's famous Vomit Comet. You can watch one of her demonstrations below.

[h/t SFGate]

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