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It's the Olympics, and it'll be one the world won't soon forget. The sprinters are in position on the starting blocks, the signal is given and the runners are off! However, one man gives off a fart so huge that it significantly boosts his acceleration. This mother of all farts propels him all the way to a first-place finish and a trophy on a pedestal. Cue a training montage flashback where our protagonist learns the art of fine muscular control in a remote mountaintop monastery.

My question is this: is it mechanically viable for a male athlete weighing approximately 80kg to use rapid anal gas expulsion (AKA flatulence) as a form of assisted take off or even as a nitro boost?

Main problems with this idea that I've identified:

  • Fart propulsion might have too low a thrust-to-weight ratio for this purpose

  • The human body might not be able to store enough gas for this purpose

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    $\begingroup$ More useful for a swimmer I would think if it's a white male athlete.... purple female would be a different story $\endgroup$ – Kilisi Oct 2 '18 at 6:27
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    $\begingroup$ Unless he had a hole in his pants for the gas to escape from, most of the speed of the gas would be lost since it needs to be pushed through the fabric. $\endgroup$ – Shadowzee Oct 2 '18 at 6:43
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    $\begingroup$ "nitro boost" increases power output in the primary mover, which would be legs in this example. What you're proposing is "assisted takeoff", commonly known as JATO or RATO. $\endgroup$ – Agent_L Oct 2 '18 at 10:14
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    $\begingroup$ In addition to the answers, please bear in mind that the human anus does not point backward at an angle parallel to the ground. Even leaning forward (running into the wind, so to speak, the runner in front of you could have this benefit, too), the angle is wrong. Were this possible at all, it would be very useful for hurdlers and high jumpers, but not for runners. It would cause you to loose too much traction on the ground. $\endgroup$ – JBH Oct 2 '18 at 14:39
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    $\begingroup$ @Kilisi: There's historical precedence for that. Olympic swimmers in the... let me tell a lie... 1980s (...? really, I'm not sure, could have been the 1970s) pumped helium in their anus to make them float better. No, I'm not joking... $\endgroup$ – Damon Oct 3 '18 at 10:19
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I don't think it is viable.

If you want to propel the athlete of mass m to certain velocity v starting from rest, you need to provide a momentum $P = m_a \cdot \delta v_a$.

The same momentum has to be given to the expelled gases. The average bowels should be around 10 meters long, and let's assume they have an homogeneous radius of 1 cm, it means the available volume of gas is about 10 liters, accounting for a mass of about 6 grams, if we assume it is fully made of methane.

It follows that, to speed jump the athlete at 10 m/s that gas would need to be expelled at $\delta v_g = m_a \cdot \delta v_a /m_g = 80 \cdot 10 /{6 \cdot 10^{-3}}= 130 \ km/s$.

Though I am not aware of any scientific study on the topic (if it exists, please submit it to IgNobel award committee), I am fairly confident that would be sufficient to blast away the athlete's lower body.

For additional reference, the SP2B 28 mm, a WWII cannon, had a muzzle velocity of 1.4 km/s, while conventional gaseous intestinal emissions have been measured at 0.003 km/s (credits @Mołot for the last reference).

Addendum

One can object that it could be possible to increase the momentum of the ejecta by choosing a denser medium.

Let's pick water, as it is convenient to assume that whatever is in the intestine is water based: 10 liters of water would weight 10 kg, so the discharge would need to happen at "just" 80 m/s. Still way faster than a conventional emission.

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    $\begingroup$ That is perhaps the smartest answer I've ever seen to the dumbest question I've ever seen. Good show sir. Good show indeed. $\endgroup$ – TCAT117 Oct 2 '18 at 7:27
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    $\begingroup$ For reference, the exhaust velocity of the Space Shuttle main engines was about 4.4 km/s in vacuum... and that's attained by combustion, not by simply expelling gas under pressure. $\endgroup$ – Jordi Vermeulen Oct 2 '18 at 11:51
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    $\begingroup$ @Hobbamok, don't forget we are not dealing with metallic container and nozzle, but with the living flesh of a human, who supposedly aims at receiving the gold medal alive. $\endgroup$ – L.Dutch Oct 2 '18 at 12:14
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    $\begingroup$ And even if the magnitude were such that the gas didn't destroy the runner's lower body, there's the loss due to collision with the fabric of the runner's shorts, unless our hypothetical runner were competing in true ancient olympic fashion -- in the nude. The gas colliding with the fabric would exert pressure on the fabric, which in turn would pull on the runner, presumably losing most of the boost. $\endgroup$ – T.J. Crowder Oct 2 '18 at 15:43
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    $\begingroup$ Mercury lowers it to 6 m/s. $\endgroup$ – Yakk Oct 2 '18 at 18:24
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Your scenario would not work, flatulence of this magnitude would not be possible.

However swimmers can do something similar in competition. Except not farting for a jet assist, but filling their bowels with gas and holding it in. This gives their bodies a fraction more buoyancy enabling them to swim just a tiny bit faster.

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    $\begingroup$ The same goes for burps. Swimmers can swallow a lot of air and train on holding the air inside their stomach. This would also balance the extra buoyancy from the back to be more in the middle of the torso. However, the space required for the extra air intake might mess up the airodynamics of the swimmer. $\endgroup$ – Mixxiphoid Oct 2 '18 at 10:55
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    $\begingroup$ @Mixxiphoid The back is where it's needed most, but makes sense if it's possible, every bit counts when they're shaving fractions of a second... makes you look closer at championship swimming events and notice the suspicious bubbles right after they get to the end. $\endgroup$ – Kilisi Oct 2 '18 at 10:58
  • $\begingroup$ @Mixxiphoid hydrodynamics perhaps? $\endgroup$ – Criggie Oct 3 '18 at 9:34
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L.Dutch had alreary given you the physical reason why it would not work. I'll focus on the biological.

For it to be possible, the guy would need a propellant like gas or diesel. We are talkung about acceleration like the famous jet bike from Jackass. Besides being too hard to control (neither that bike nor you have thrust vector control) the anus of the runner would probably explode from the pressure.

Supposing the guy has an artificial anus that is made of steel, there is still the problem of expelling the gas in force. You would need a lot force in the intestines. That would draw blood to them, and hence away from the legs, which goes counter what he wants to do.

Also, if you want to feel the discomfort the athelete would feel just by trying to run with gas, go eat half a pound of mexican beans then do a sprint. Remember to bring a roll of toilet paper to the exercize.

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You made reference to a 'nitro boost' in your question. If this takes precedence over the concept of the flatulence creating some form of 'jet' effect, then maybe we have something to explore. I have read the question carefully, and I do not read anything in it that specifically relates to the jet propulsion effects. Rather, it seems to be able to be interpreted as relating to any effects on the maximization of energy creation and utilization.

Nitrous oxide does not in itself combust. What it does, when used in engines, is to provide more oxygen (the oxide part) for combustion. The gas decomposes at gas engine temperatures into nitrogen and oxygen. (Injecting pure oxygen would give a similar but perhaps more hazardous and difficult to control boost in combustion).

So, given that:

  1. many farts are methane gas.

  2. increased oxygen intake adds to human performance.

  3. the flatulence results in a reduction in air pressure in the intestines.

  4. the Bernoulli effect uses air flow to compound air flow.

  5. the lungs would be the benefactor of this increased or enhanced air flow, as they are in the same air pathway as the intestines.

  6. Olympic sprints are determined by hundredths of a second difference in timing.

  7. the flatulence would lead to an expansion of the methane gas

  8. methane is lighter than air, and the sprinters' shorts would fill with methane, making the runner ever so slightly lighter (but counter to the relationship to Nitrous Oxide, which is heavier than air).

  9. the expelled methane would change the air flow dynamics, if even so briefly, behind the sprinter.

  10. even a misplaced seam in the uniform of a sprinter could make the difference between winning and second place.

If we are looking for a performance boost in terms of hundredths of a second, I think we have enough factors that could make this question a good candidate for a Mythbusters Episode. And, of course, it does fit with their overall theme.

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Maybe a competitive advantage could be gained on the swimmers in the lanes immediately to the right and left of the subject. Say if they ate nothing but White Castle with double onions for 3 days prior to the event, when those swimmers to the immediate right and left turn their heads for a quick gulp of air...if all they get is a gulp of White Castle exhaust...that might at least provide a competitive boost

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    $\begingroup$ Can you explain what is this White Castle, for those who have no clue? $\endgroup$ – L.Dutch Jul 27 at 7:42

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