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Astronauts dread pooping in a zero-gravity environment. They dread it so much that they’ll take extreme measures to avoid doing it: some simply stop eating; others medicate themselves into constipation.


Like many aspiring space colonists, I’ve always assumed that living in a zero-g environment would be nothing but carefree fun. Mary Roach, in her book Packing for Mars: The Curious Science of Life in the Void, shatters that illusion.


Many biological functions that we take for granted here at the bottom of Earth’s gravity well are problematic in free fall. Mary Roach devotes a chapter to each type of difficulty. Some issues are well-known:

  • space sickness: the weightless version of sea sickness
  • eating: it’s difficult, because the food tends to float around and make a mess
  • crowding: space habitats tend to be small and crowded, with no privacy whatsoever
  • isolation and confinement: the space version of cabin fever afflicts astronauts on solo missions
  • muscle and bone deterioration: our bodies need gravity to stay in condition

However, there are two aspects of human biological function that are little publicized or thought about: hygiene and elimination. In space, hygiene is a nuisance; elimination is a nightmare.

Hygiene in Space

Showers don’t work well without gravity. When the water sprays out of the shower head, the drops either collect into a blob and float away, or hit your skin and ricochet off. Astronauts don’t even try to use showers anymore; they make do with moistened towels and rinseless shampoo.


Your skin is constantly shedding flakes. Here on Earth, those flakes fall to the floor and help make dust bunnies. In zero-g, they float in the air until you inhale them.

Elimination in Space

There are pressure sensors in the bottom of your bladder that tell you when it’s time to pee. They don’t work very well in zero-g, because urine collects on the walls of your bladder rather than pooling at the bottom where the sensors are. As a result, you don’t realize that you need to pee until your bladder is almost completely full. If your bladder gets too full, it squeezes your urethra shut so that you can’t pee. You then have to be catheterized. Ouch!


The early approach to defecation in space involved crapping in a plastic bag. The procedure took forty-five minutes, and had to be performed in full view (and smell) of everyone in the cabin. Frequently, the star of the show didn’t manage to seal the bag properly when the performance was over. This resulted in “escapees”—human turds floating freely around the cabin.


In response to complaints about the fecal bags, engineers have developed various zero-g toilets, but these devices also have their problems. The toilets have very small openings, and without gravity to help you aim, it’s easy to miss, resulting in more escapees. Space toilets are now equipped with rear-view mirrors.


One of first toilet designs featured blender-like blades that pulped feces and tissue and plastered them to the walls of a holding tank. This design had the unfortunate side effect of filling the cabin atmosphere with fecal dust. Later designs were plagued by a problem called “fecal popcorning”, which involves junior-sized pieces of feces being ejected into the cabin atmosphere.


These are only a few of the bizarre and unwholesome aspects of the weightless lifestyle that Mary Roach discusses in her book. I’d recommend this eye-opening book to anyone who is interested in exploring the less glamorous side of space travel.


One Comment

  1. And you wonder why George Jetson’s boss was always so angry? 🙂

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