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labroid t1_j10wl8x wrote

Reply to comment by Jagid3 in Could being submersed in a sealed tank of fluid help humans survive heavy G acceleration in outer space? by cheeze_whiz_shampoo

I don't think this helps, since at high accelerations the pressure gradient in the water will probably kill you. (See longer answer below)

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MidnightAtHighSpeed t1_j115azp wrote

Why would the pressure crush you? There's not really anything compressible in the human body besides air pockets, is there? Isn't the biggest problem with high-pressure diving breathing gas?

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labroid t1_j116lvp wrote

The pressure gradient is the problem. If you were 'vertical' (head in direction of acceleration) the pressure on your toes and legs at 100G would be, let's see: 62.4 lbs/ft^2 / 144 in^2/ft * 100G * 6 ft = 260 PSI while your head would be 62.4/144100.5 = 21 PSI. So basically your legs will be squeezed into your chest and head. Not good. (Sorry for the stupid Imperial units...)

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labroid t1_j1173bm wrote

To add more fun, if your foot is about a foot long and about 3 inches wide and a couple tall, you have about a square foot of skin, so there would be 144 * 260 psi = 37,440 lbs (or ~19 tons) of force squeezing the contents of your foot up your leg into your head like toothpaste.

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mutandis57 t1_j133ukp wrote

Not to mention the blood still needs to circulate in your body. Trying to pump blood up to your head 0.5m above your heart at 100G is equivalent to your neck being 50m long. Your heart is not as strong as a giraffe's! Not gonna happen without some form of suspended animation.

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mutandis57 t1_j1336dz wrote

This is why everyone thinking that water suspension will allow humongous accelerations is deadly mistaken. Being underwater at 1km IS NOT THE SAME as accelerating at 100G in a water bath. Not the same! At 1km you have 100atm of pressure on all sides. You can probably scuba dive at 1km just fine if you descend slowly and prebreathe the right gas mixture. Sitting in a 1m tall chair in a water tank at 100G, your head is at 1atm and your feet are at 100atm. This is different! You'll be crushed like a bug. Filling your lungs and other body cavities with water or perfluorocarbons or whatever will not help!

A water tank should instead be thought of as the most comfortable acceleration couch possible, that supports every part of your body with the highest softness possible and no pinch points. You'll also do best if you lie perfectly flat horizontally, instead of sitting or standing.

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