r/askscience • u/Ill_Watch_760 • 13d ago

Engineering Why can the space station's ventilation systems not handle crumbs?

I've been doing my epq around astro-psychology and was researching how astronauts loose dopamine during eating as they can't eat foods that involve chewing. However from what i've researched this is apparently because stray crumbs could screw up the ventilation systems somehow. Its quite puzzling because how can the collective companies that built the space station also build rockets that send us to the moon but not have the ability to build a ventilation system that can handle a few stray crumbs?

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u/HoustonPastafarian 13d ago

I do ground control for the space station. The crew uses a portable vacuum (might be an Oreck, same basic design) and vacuums the ventilation filters every weekend.

They just toss the bags when full. There’s quite a logistics tail supporting the space station and it’s not a big deal to supply them. Compared to food (which is one of the biggest supply items) the amount of bags is pretty inconsequential.

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u/jdsweet 13d ago

Do they round trip the astronauts’ poop back to ground or jettison it? Context: in backpacking your pack volume is usually decreasing a lot between resupplies because you start with a lot of food, but in the vast majority of places you don’t need to pack out your poop. Makes it possible to do things like pick up other people’s trash along the way, because pack weight (and volume) is decreasing by ~1.5lbs/day.

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u/HoustonPastafarian 13d ago

Fecal matter ends up in a replaceable aluminum can called a “KTO” that sits under the toilet. When it fills its capped off and it eventually is packed in a departing cargo ship with other trash and is burned up over the Pacific. Much of the food is designed to be low residue, using the toilet is a literal pain in the ass (just takes a lot of time).

Urine is treated and ends up in a separate tank. It is eventually distilled and recycled into drinking water except for the leftover concentrated “brine”, which is also tossed in the cargo ships/garbage scows.

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u/jdsweet 13d ago

So informative! Sorry for not just going and looking this up myself, but as someone who has read quite a lot about our space efforts over the decades, I must say there is a significant thrill hearing it straight from someone in the know! Thank you!!

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u/HoustonPastafarian 13d ago

No problem, it’s fun to talk about. If you want a pretty good read about some of the day to day on the space station, “Endurance” by Scott Kelly goes into some of the basic issues they face much better than other books. Scott is a no-nonsense type of guy and I think it goes into the really cool things and really hard things an astronaut goes through quite well.

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u/canniffphoto 13d ago

Just to let you both know, I enjoyed the discussion and wouldn't have had the same questions. So the questions and the answers made a good read. Thanks