I am NOT trying to be lewd, but I had a student ask this. Yes, she may have been tongue-in-cheek, but I promised to answer her. And yes, I am trying to keep this as practical as possible.

If and when someone passes gas while in a space station (contained environment in microgravity), would there be enough acceleration to push the person into another position? I don't need direct math, or even biology, but I'd like to return an answer to my student. My suspicion is, physically in a vacuum, yes of course, but on, say, the ISS, would it really direct you?

I am not trying to be lewd, but genuinely want to know the magnitude of order of a fart within the confines of a habitable space station in microgravity to answer her question. If there is literature on it, that's great.

I have great respect for the SE community: so please don't think I'm being silly; I'm happy to have this removed if you find it inappropriate; but I promised a space answer.

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    $\begingroup$ These is a very good video on channel PBS space time titled "Could you fart your way to the moon?" I think it is related to your question. link $\endgroup$
    – Knu8
    Commented Oct 24, 2016 at 11:34

1 Answer 1


I'll try. Please don't judge.

Say, 5 liters of carbon dioxide (a guesstimate of about how much of bowel volume could be occupied by a single pocket of gas; may not be average or maximum, but is within realm of 'possible'), at 30km/h (when I happen to release one while wiping myself, it feels roughly as if I put my hand out of a car window at such speed; again, a 'possible' speed.)

The wet mass to dry mass ratio (...sorry) is small enough that we won't need the rocket equation. CO2 density of 1.98 kg/m3, rounding to 2 (pressurized!) gives 10 grams to 5 liters. With conservation of momentum, the gas gets 8.3m/s*0.01kg = 0.083 kg*m/s. If the astronaut is 50kg, it will yield 1.6mm/second worth of delta-V.

With constant air circulation enforced by ventilation of a space station the acceleration effect would be entirely unnoticeable

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    $\begingroup$ My answer to this related question space.stackexchange.com/questions/18386/… describes how an astronaut actually tried this and sneezing and spitting didn't work. So farting likely wouldn't either, as you say. $\endgroup$ Commented Oct 22, 2016 at 22:49
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    $\begingroup$ So much for farting our way to Mars... :-# $\endgroup$
    – agtoever
    Commented Oct 23, 2016 at 14:26
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    $\begingroup$ Well most of the plans to send people there are just so much hot air. $\endgroup$
    – GdD
    Commented Oct 24, 2016 at 13:01
  • $\begingroup$ Also I didn't figure much of the fart's exhaust is slowed by the clothes you're wearing. Anyway, I used your answer. Half a decade ago lol. $\endgroup$
    – Mikey
    Commented Jul 9, 2021 at 21:01

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