NASA is developing a new space toilet for moon-bound astronauts — but the agency's 'certified sniffers' say the system is far too stinky

• NASA plans to use its Orion spacecraft to fly astronauts to the moon.
• But first, engineers have to figure out how to make the capsule's toilet less stinky.
• A model of the toilet is launching to the International Space Station next week, where astronauts will test it out.
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NASA is actively preparing to send astronauts back to the moon for the first time since 1972. The agency plans to send a crew on a 10-day flyby around the moon in 2023 on its Orion spaceship, followed by a mission to land people to the lunar surface in 2024.

But on those missions, the astronauts will need a way to go to the bathroom. This presents a unique challenge for Jason Hutt, engineering lead for the Orion capsule.

Hutt is responsible for ensuring that Orion's toilet, called the Universal Waste Management System (UWMS), can function within the confines of the spacecraft without creating excessive mess or smell. Given that Orion is only the length of a small powerboat and must house four waste-expelling adults for nearly a month, the system has to be compact, efficient, and not too stinky. 

"If you want to recreate that used spacecraft smell, take a couple dirty diapers, some microwave food wrappers, a used airsickness bag, & a few sweaty towels, put them in an old school metal trash can and let it bake in the summer sun for 10 days," Hutt wrote on Twitter in August. "Then open the kid & breathe deep."

A version of the new toilet is launching to the International Space Station next week, where astronauts will test it out by installing the system it next to one of the current ISS toilets.

Astronauts' pee could float in space forever

The UWMS design isn't too different from other space toilets. Because there's no gravity in space to help flush waste downward, it uses motorized fans to suction away astronauts' urine and feces.

The poop would remain stored on Orion until the ship returns to Earth. But there won't be room to store pee, and the spaceship can't recycle it into water the way the space station can —there's not enough space for that kind of filtration system.

So the plan is for Orion astronauts to vent their pee into space, where it could float frozen forever (the temperature is -455 degrees Fahrenheit).

NASA has vented astronauts' pee into space before — the Space Shuttle toilet did the same thing. But during those flights, the urine froze onto the vent. This time, engineers are adding heaters into the system to prevent immediate freezing. 

Because Orion is small and weight requirements are extremely strict, the toilet has to be lightweight, as do its fans and motors. But relying on small motors for powerful suction forces them to be very loud. Plus, since Orion is mostly made of aluminum alloy – it's "a big aluminum can," Hutt told Business Insider – the noise of whirring fans, clicking valves, and clanking machinery machine reverberates throughout the ship. 

That makes for a noisy toilet, but there's an upside: Toilet users get some privacy, since Orion's bathroom has only a thin door separating it from the rest of the ship. 

Astronauts can't use Febreze 

Storing human waste on the Orion capsule for weeks at a time means engineers have to figure out ways to tamp down the stench.

Any filters NASA uses for this have to be effective yet compact so they don't add too much weight.

"Odor is really caused by the chemical compounds released from human waste breaking through the filter that's supposed to remove those compounds," Hutt said. 

If odors do escape, astronauts have very few options to combat them.

"You can't just open a window whenever something smells bad," Hutt said.

NASA also can't allow chemical deodorizers, like Febreze, on spacecraft — they would pollute the air too quickly, potentially harming the astronauts inside. Plus, pressurized canisters aren't allowed given the risk they could explode. 

"Spaceflight has its share of bumps, and we don't want anything in the cabin that could become a hazard," Hutt said.

So Hutt's team tests many potential deodorizer options. So far, the safest one they've experimented with is activated charcoal, a powdered charcoal that absorbs odors without requiring electricity or chemicals. The substance can be put into a filter in the ship's ventilation system.

These tests, of course, require human noses. NASA employs "certified sniffers" at its White Sands Test Facility in New Mexico, who, true to their title, are paid to smell the toilets after they've been used to evaluate whether odor-control measures are working.

These sniffers are the "unsung heroes of the space program," Hutt said.