Aerospace engineer here. To levitate, the force of the exhausted mass flow (F=ṁ×v) has to equal the pull of gravity (F=m×g) on your body. The gravity of earth is g=9.81N/kg. Wikipedia says the average body mass is 62kg. It also says the bladder capacity of an adult is about 400ml, and I’ll assume the density to be 1kg/l. You want to levitate for 2 seconds, so your mass flow needs to be ṁ=0.4kg/2s=0.2kg/s. If you rearrange the equation, you get v=m×g/ṁ=62kg×9.81N/kg/(0.2kg/s)=3041m/s.
So if you manage to pee with a velocity of about 3km/s, you can levitate for 2 seconds with an average sized bladder.
To achive that, your “exhaust” must be clenched to a diameter of about 0.29mm. This gives a cross-section of 0.066mm² or 6.6×10^-8m². Multiply that with the velocity of 3041m/s and you again get your flow of 0.2l/s.
Of course, during those 2 seconds you loose mass and therefore, earth’s pull on you gets less and you start to accelerate to about 0.23km/h, reaching a height of 4cm. If you took your special bladder to space, we can use the rocket equation to calculate that this stunt would accelerate you to 3041m/s×ln(62kg/61.6kg)=19.7m/s=71km/h
Beautiful, I was waiting for an engineer to do the calculations … so in layman’s terms, clench your urethra, push your bladder as hard as unhumanly as possible and hope to everything that is holy that your entire urinary tract doesn’t explode before your urine leaves your body.
I guess we’ll have to keep experimenting to determine which parts need the reinforcing in order to achieve our goal of two second levitation
This sounds like the perfect thing for whatif by xkcd
According to one of my favorite shorts of all time, the answer is “I don’t know”
I implemented a realistic physics simulation that answers this question for Diarrhea.
For a water powered jetpack to lift a person it is estimated to need at least 100 gallons per minute, so similarly this could be what would be needed. Even for a second, a person’s bladder would need to be 1.6 gallons and expelled at a similar pressure. So not two seconds.
3.2 gallon bladder to achieve 2 seconds? And what kind of pressure are we talking, would it just like totally blow your dick off or what
I mean a bladder can’t even hold a fifth of a gallon (more like 500ml) so we are already saying it is not possible but assuming there in the future is a human cyborg or a robot the same mass and volume as a human, they would need 60psi and 3.33 gal capacity for two seconds. This info is based on water powered jetpack companies that do this service. So, I did over look one thing: the jetpacks are dual and attached to your legs and they happen over water so not sure the rest of the calculations because I am not certain whether each jetpack has same psi for it to work or it is a combined psi and the water just comes from a hose so there is no capacity but the speed needs to be at least 100gpm.
You may need to double the flow. With the water powered jet packs the water isn’t just being accelerated from a standstill. The water is first flowing up with close to the same speed and is redirected down. So the momentum exchange is twice what it would be if the water were stored in tanks with the flyer.
Well, for a minute of water jetpack it is 100 gpm, so I divided 100 by 60 seconds to get 1.6… for one second so two it would be 3 and a third gallons for two seconds assuming the right pressure of 60 psi.
Your urethra is going to be really fucking sore.
