Could You Fart Your Way to the Moon?

Fart-powered space travel fails for a simple reason: there isn’t enough expelled mass to generate meaningful momentum in the long run. Rockets work by throwing mass one way so the rest of the system moves the other way, and the same momentum-conservation rule applies to any “gas rocket,” including flatulence. In space, where there’s no air to push against, the only way to move is to eject something—so the question becomes whether a human can eject enough gas fast enough to matter.

The analysis starts by clearing up a common misconception: rockets don’t need to “burn” to accelerate. Any mechanism that ejects mass at high enough speed produces thrust, because the ejected material carries away momentum and the rocket must recoil to keep total momentum balanced. Chemical rockets achieve that by heating propellant until it expands into fast-moving gas particles that escape the nozzle; the same thrust could be produced in principle by non-burning “throwing” systems, as long as enough mass is expelled sufficiently fast.

Turning to farts, the episode treats flatulence as “throwing gas” and estimates the recoil from typical human output. Using an exhaust speed estimate of about 3 meters per second and an estimated total mass of roughly one gram of flatus produced over 24 hours, the recoil speed comes out to only about 43 microns per second. That translates to roughly 1.3 kilometers per year—so slow that even in a vacuum it would take hundreds of thousands of years to cover the Earth–Moon distance, and the situation is even worse once gravity is included. The core bottleneck is mass: even if the gas exits, the amount of gas is too small to build up useful momentum.

The discussion then shifts from “moon travel” to a more realistic emergency scenario. If someone were stranded 10 meters from an airlock on the ISS, farting could, in principle, get them there—over about two and a half days if they build up and release gas in bursts (or about three and a half days if they take a full 24 hours to accumulate the roughly one gram). Sneezing is suggested to be similar in effect because its mass and exit speed are comparable to farts.

Peeing, however, changes the math dramatically. Urine streams are estimated to exit at roughly 3–4 meters per second, and a full bladder holds about half a liter—around 0.5 kilograms. That’s roughly 500 times the mass of a day’s worth of gas, so momentum conservation implies a recoil velocity about 500–700 times larger. The result: a recoil speed on the order of tens of meters per hour, enough to return to the ISS in under eight minutes.

The episode closes with a blunt comparison: to match urine’s effect with farting, the required exhaust velocity would need to exceed Mach 4 (over 3,000 miles per hour), far beyond anything achievable by “nozzle engineering.” The practical takeaway is that sideways farting is technically possible but wildly inefficient, while peeing—or simply throwing something heavier—would produce far more recoil.