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  • [♪ INTRO]

  • In the past, we've discussed how astronauts relieve themselves in space,

  • and even what can be done with their pee.

  • But there's another, darker side of this story: astronaut poop.

  • Right now, astroturds become a magical light show, in that they are ejected from the ISS

  • to fall back onto the Earth and burn up in the atmosphere.

  • So you can think about that the next time you see a shooting star.

  • But there are so many things we can do with poo!

  • Waste is the enemy in matters of space exploration,

  • and that includes the bounty our bodies give us. So let's use it!

  • Now, there is a caveat to this: obviously,

  • all poop needs to undergo a great deal of processing before it can be useful to us.

  • But there are tons of great poop processors out there, in the form of microbes!

  • Lots of microbes eat poop. They love it. And there's a bunch already in your poop;

  • they're kind of responsible for poop's whole deal.

  • But a couple of special species of microbe eat poop and produce plastic.

  • These microbes, Ralstonia eutropha and Pseudomonas aeruginosa,

  • produce polyhydroxybutyrate, or PHB, for energy storage; similar to how we use fat in our bodies.

  • That PHB is literally a biological plastic, and it can be collected, purified, and fed into a 3D printer.

  • Now, P. aeruginosa can cause pretty nasty infections depending on how healthy your immune system is,

  • so astronauts probably don't want to culture it up in space.

  • And while R. eutropha isn't pathogenic, it's still not the lab microbe of choice. That is E. coli.

  • It's about as safe as a microbe can get, provided you're working with a safe strain.

  • We know it really well, and we've already grown it in space!

  • Plus, it's easy to clone genes from other microbes into E. coli.

  • So that's what's being proposed by researchers at the University of Calgary:

  • clone the PHB-producing genes into E. coli, and let them eat poop. In space.

  • In addition to the bio side of the equation, the tech side has been fully developed,

  • including a system to 3D print plastic objects using PHB from these bacteria.

  • So astronaut poop can become, say, replacement parts on the ISS,

  • or building material if, or when, we settle on Mars.

  • Speaking of settling on Mars, what are we going to eat when we get there?

  • The answer is actually less gross than you think, given the general premise of this episode.

  • The plan is to once again feed our poop to some microbial intermediaries,

  • but this time they're helping us make food.

  • So while the astronauts aren't eating poop, it is involved in their food supply.

  • But then again, we've been using manure as fertilizer for ages, so it's not that weird.

  • So the idea, from a paper published in 2017, is to take the raw waste,

  • and mechanically process it into carbon dioxide and methane, plus some leftovers.

  • Then, a microbe by the name of Methylococcus capsulatus eats the methane

  • and produces proteins and fats, which we would extract and use as a nutritional supplement.

  • Alternatively, to distance ourselves from the ick factor,

  • we could feed it to other organisms, which we'd subsequently eat.

  • The authors of this plan propose feeding it to fish or grubs.

  • And any water produced in the process can be captured and purified,

  • so it's a really low-waste approach to your waste.

  • The first two options are pretty reasonable, when you think about it.

  • They rely on some very well-tested and clear principles,

  • even though the applications sound a little sci-fi.

  • But what if we just went full sci-fi for a minute?

  • Because I've got to tell you about Water Walls.

  • These are hexagonal bags attached to the walls of a spacecraft

  • that are networked to produce a full life-support system. Using poo.

  • There's a bag for initial waste processing, for growing algae to eat,

  • for water purification, for humidity and climate control, for fuel production.

  • It's got everything. And it's a pretty simple setup:

  • the bags start with a soup of all the chemicals and microbes needed to do their jobs,

  • and the end product from each bag gets sent to the next bag in the network through a filter.

  • The crew provides the raw material.

  • And then the bags line the walls of your spacecraft or habitat,

  • the ISS, your Mars ship, your moon pod, whatever, to provide radiation protection.

  • Water makes a good radiation shield because it has a fairly low molecular weight.

  • Heavy molecules basically just get in each others' way

  • and limit how well they can absorb radiation, so the lighter the better.

  • That said, water is pretty dense, so a pure-water shield would weigh too much to be practical,

  • but water plus chemical soups plus the bags containing them is a totally viable setup.

  • This may sound like it comes straight out of Star Trek,

  • but it's been in development at NASA's Ames Research Center for a long time,

  • and was even slated to fly on a private, long-term Mars mission.

  • But that mission was Inspiration Mars, in which noted rich-guy-who-likes-space

  • Dennis Tito wanted to send a married couple to fly around Mars, but never land.

  • This mission did not happen for a number of reasons,

  • including NASA not dropping everything they were doing to help out a random multi-millionaire.

  • Not even fellow rich-guy-who-likes-space Elon Musk was willing to throw money at the venture.

  • But while the mission may have been somewhat ill-advised

  • and ultimately never took off, the Water Wall technology is actually viable.

  • NASA has even made it available for licensing,

  • so companies like SpaceX can take advantage of it in private space enterprise.

  • And there you have it.

  • In space, you use everything at your disposal, and we mean everything,

  • to make the mission a success.

  • Including stuff you've already disposed of.

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  • [♪ OUTRO]

This episode is sponsored by Squarespace.

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如何處理這些空間便便 (What to Do With All This Space Poo)

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    林宜悉 發佈於 2021 年 01 月 14 日
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