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labroid t1_j10xs7f wrote

Reply to comment by JonJackjon in Could being submersed in a sealed tank of fluid help humans survive heavy G acceleration in outer space? by cheeze_whiz_shampoo

Don't think so. Position in the tank is determined by the person's buoyancy and the water pressure gradient, and both of those are determined by gravity on earth, and acceleration in space. The person should stay at the same position

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JonJackjon t1_j11vspz wrote

Think so. The OP specified "submerged" so the buoyancy will only determine where in the tank they are.

But no matter how you look at it, if the tank and water accelerates, the body will accelerate as well. So there will be no reduction in the stress resulting from acceleration.

If you don't believe this simply take a glass of water, put something in the water. Accelerate the glass with the water (upwards). The item in the water will feel the same acceleration as the glass.

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labroid t1_j11xcll wrote

Agreed. Body won't hit the bottom of the tank, but the acceleration on the body will be identical. Being submerged avoids impact concentrated pressure on contact points (as you'd get from being in a seat) but acceleration on the body as a whole is identical.

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JonJackjon t1_j12j1yd wrote

What forces would stop the body from hitting the bottom of the tank?

If you held a penny midway in a glass of water, the released the penny, gravity ( a similar force) would cause the penny to drop to the bottom.

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labroid t1_j13odyh wrote

I assumed the OC meant the person was floating in the water, so buoyant forces keep it at the top. When you accelerate, the person's weight increases, but the buoyant force increases exactly the same amount, so everything would stay where it was.

If it were a penny, then you are right - it would already be on the bottom and would stay there.

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Game_Minds t1_j110ouz wrote

Only if the persons density changed at the same rate as the water. Our body would be pushing outwards to maintain a lower internal pressure, making us more buoyant

Makes me think of another question, would the pressure change or the marginally increased g forces kill you first in this experiment

Edit: Another hilarious question... would the water heat up? Increasing pressure rapidly in an incompressible liquid produces heating, see: refrigeration

Would you scald to death, die of a stroke when your gas-free blood still pools in the back of your skull, or die of internal pressure gradient because your cells stop working and burst

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JonJackjon t1_j11waim wrote

>Edit: Another hilarious question... would the water heat up? Increasing pressure rapidly in an incompressible liquid produces heating, see: refrigeration

No, refrigeration depends on the change of state liquid <--> gas of the refrigerant.

I agree a gas will become hotter when compressed. Simply because the "heat" will exist in a smaller volume.

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Game_Minds t1_j121hdb wrote

I did way too much thinking about this today lol

It would be a super small amount of heating unless the acceleration was relativistic, so negligible

The separation effect of the acceleration (centrifuge forces) would also be pretty small at all but very high accelerations

And the amount of damage caused by the acceleration would be a lot smaller without any gas at all-- BUT gas is a byproduct of a large number of our body processes like oxygen uptake, AND that acceleration would still have a meaningful effect on your body's different systems. You would still die of a stroke at pretty small accelerations

Edit: also good call! I totally forgot about the latent heat of vaporization thing being the primary factor

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