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Jagid3 t1_j0zyfxl wrote

You would need to fill every air filled cavity in their body with the fluid and then they would be fine.

If you missed any they would become compressed and could possibly cause damage depending on how big they are and where they are.

Of course they would need to be able to survive in the fluid. Any normal fluids we have these days would certainly kill them.


cheeze_whiz_shampoo OP t1_j0zziel wrote

I was imagining filling the lungs with an oxygenated fluid. My brain was just hopping around and I realized I couldnt even imagine what would happen to someone suspended in liquid and undergoing acceleration.


Origin_of_Mind t1_j117dk8 wrote

Suspending an organism in a density matched fluid could be used to increase the survivable acceleration, but the gain is limited, because different constituents of the body have different density. For example, fat is 0.9 g/cm^(3), while cortical bone is 1.9 g/cm^(3). If the average density were matched by the fluid, the internal stresses due to differences in density of individual parts will remain unchanged, and these differences are of the same order of magnitude as the difference between air and body density.

So, yes, it would work, but the payoff is not too great.


Game_Minds t1_j12pvb7 wrote

To paraphrase something someone said elsewhere in here, it would allow humans to achieve ludicrous relative accelerations compared to normal human expectations, but that would still be extremely negligible acceleration compared with trying to achieve relativistic speeds

And as a third person said, the cost of transporting and manufacturing this fluid would probably significantly outweigh any gains


Origin_of_Mind t1_j12yeoh wrote

Human ability to withstand acceleration is not a limiting factor in long range space travel.

With the astronauts experiencing just the ordinary 1g of acceleration all the time they would be able to get to anywhere in the visible universe and get back to Earth in just 100 years (from the point of view of the astronauts themselves.)

But even accelerating the rocket at 1g for more than a few tens of minutes is already beyond our present technology.


Game_Minds t1_j14d8b6 wrote

I think the idea of the extreme accelerations is that you could use something like a nuclear bomb to clear the first few stages of accelerating and then your onboard fuel supply doesn't have to work as hard, but I think there are more reasons than the G forces why that wouldn't work either. We don't have the tech for much more than 1g of sustained thrust anyway, like you said. These kinds of thought experiments are the very definition of speculative lol


zyiadem t1_j118dq9 wrote

Our diaphragms are not made to move liquids, and such experiments that have explored this required a Specalized ventilator to avoid permanent damage to the body.


Game_Minds t1_j12py78 wrote

And we all know being hooked up to a specialized ventilator for extremely long periods is perfectly healthy and fine


labroid t1_j10wl8x wrote

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


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?


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...)


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.


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.


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.


InTheEndEntropyWins t1_j10620x wrote

How would filling someone with fluid help?


annomandaris t1_j10lffz wrote

air compresses, so if you have air in your lungs, and accelerate, the lungs will collapse.

If there was fluid inside and outside the lungs, there would be no compression of the lungs, its like how a bottle can fall to the bottom of the ocean and not break.

But yea you have to get them all, fill the empty stomach and bowels, nasal cavaties, lungs,


Tanagriel t1_j113t53 wrote

In the fiction movie “The Abyss” from 1989, they use a breathable fluid as to endure the pressure at deep ocean. Quite well made scene in how they need to control the body symptoms of drowning when taking the fluid into the lungs. ✌️


--VoidHawk-- t1_j11no0m wrote

A similar solution has been described in a number of science fiction works.

My favorite solution was in the Hyperion cantos. Just let the meat get splattered by the massive accelerations used for travel, which then gets reconstructed once the passenger reaches their destination, thanks to a weird tech/bioform they discovered.


phred14 t1_j11puxg wrote

In "The Forever War", by Joe Haldeman, they used fluid compression to survive extreme acceleration in their starships. Most of the time was shirt-sleeves, but when they went into battle, it was "into the tank." He goes into a fair bit of gory detail about the discomforts of it. Frequently better science fiction authors will have some amount of research behind what they write, but I have no idea what research he might have done back in the mid-1970s when this was written.


slashdave t1_j11t701 wrote

In the UFO TV show, the aliens space suits were filled with blue liquid for breathing. This idea turned into a plot device later in the series (the aliens were very human looking, with a blue skin color only due to this liquid staining their skin).