G-Force and Water: Can Submersion Help?

[CosmicVoyager]

Greetings,

Would submerging a human in water, such as by filling the cockpit, eliminate pressure from G force in a rocket launch?

Thanks

 

[G037H3]

it wouldn't eliminate it...would reduce it

 

[russ_watters]

What pressure? It may help distribute the force on the outside of your body a little more evenly, but I'm not sure of that - your body isn't all of the same buoyancy and you may find yourself contorted by even partial submersion (your lungs would try to float, everything else would try to sink). It will not help with your breathing or circulation. Blood will still pool toward the lower parts of your body and your diaphram still has to move all of your compressed guts away from your lungs.

All in all, I would think laying on memory foam would be better.

 

[CosmicVoyager]

If you are floating in a sphere of water and accelerated at 100 G's on a rail gun launcher, what effect would it have on you?

 

[einsteinoid]

I'm assuming you would black out pretty quickly and if the acceleration was sustained for a while I imagine you'd be lucky to survive with brain damage.

 

[CosmicVoyager]

I just saw a video on the Science Channel where they put a water balloon in a jar of water and put it in a G-force rotational machine. The balloon did not move and was not deformed. The G force seemed to have no effect on it.

 

[russ_watters]

If you are floating in a sphere of water and accelerated at 100 G's on a rail gun launcher, what effect would it have on you?

I'd expect all of the bood vessels at the back of your head to rupture and your brian to crush itself against the back of your skull, with your eyeballs driving themselves through your brian. Your heart would be pressed against your back by your crushed ribcage and unable to pump. Your jaw may also rip off and crush your windpipe.

 

[CosmicVoyager]

I'd expect all of the bood vessels at the back of your head to rupture and your brian to crush itself against the back of your skull, with your eyeballs driving themselves through your brian. Your heart would be pressed against your back by your crushed ribcage and unable to pump. Your jaw may also rip off and crush your windpipe.

Hmm, what I don't understand is why would your brain get pushed against the back of your skull and your skull not move through the water instead. But then I would not expect the head to move through the water if it is neutrally buoyant. It seems like a paradox. I do not understand what is going on.

 

[D H]

I just saw a video on the Science Channel where they put a water balloon in a jar of water and put it in a G-force rotational machine. The balloon did not move and was not deformed. The G force seemed to have no effect on it.

The contents of that balloon had exactly the same density as the surrounding medium. The balloon has no

• Air-filled lungs that are a lot dense than water and are filled with a compressible gas,
• Blood vessels filled with a flowing, viscous liquid that is about 6% denser than water, or
• Bones that are about 50% denser than water.

So not quite an apt comparison. Those air-filled lungs in particular will create problems. Filling a person's lungs with perfluorocarbon would reduce these problems by quite a bit were it not for the fact that perfluorocarbon is about twice as dense as water.

 

[ThomasEdison]

http://en.wikipedia.org/wiki/Liquid_breathing

"Liquid breathing has also been proposed for use in deep diving and space travel."

I'm assuming the proposed idea is to eliminate the air in lungs problem already mentioned for short times during hard acceleration.

Bones and blood vessels might be a problem but perhaps when air filled lungs are taken out of the equation I would think that at least they could experience more g's than normal.

Edit: Its the same deal as that liquid breathing mouse. I just did not like the only youtube clip available for the liquid breathing mouse because the narrator sounded like a used car salesman.

 

[russ_watters]

Hmm, what I don't understand is why would your brain get pushed against the back of your skull and your skull not move through the water instead.

Well both would happen if you have enough water. As I said, your head is heavierthan water, so you'd only want the water deep enough that it could only be partially submerged (unless you add drowning to the list of ways to die).

But then I would not expect the head to move through the water if it is neutrally buoyant. It seems like a paradox. I do not understand what is going on.

If your head was neutrally buoyant, it wouldn't move, but your brain would still crush itself.

Consider this: does the pressure at the bottom of your tank of water stay the same regardless of acceleration?

I just saw a video on the Science Channel where they put a water balloon in a jar of water and put it in a G-force rotational machine. The balloon did not move and was not deformed. The G force seemed to have no effect on it.

Assume there was a pressure gauge inside the balloon. What would you expect to see on it as the centrifuge spins-up?

 

[Buzzworks]

Water could be used for up to several G's. I think such experiments were conducted (not really sure if memory serves me right) on an early G-suit filled with water. The problem is the suit is too heavy and somewhat more trouble than help! Modern G-suits automatically inflate/deflate on specific areas, with air. Lighter, and therefore, suitable enough for use in combat situations (not just sit and let the computer fly for you)

However, I agree with Russ and D H has mentioned previously. 100G is a completely different ball game. For that, you don't need a water tank, you'll need a pretty exotic solution, artificially generated gravity(fiction) being one of them!

 

[CosmicVoyager]

Thanks :-)

The contents of that balloon had exactly the same density as the surrounding medium. The balloon has no

• Air-filled lungs that are a lot dense than water and are filled with a compressible gas,
• Blood vessels filled with a flowing, viscous liquid that is about 6% denser than water, or
• Bones that are about 50% denser than water.

So not quite an apt comparison. Those air-filled lungs in particular will create problems. Filling a person's lungs with perfluorocarbon would reduce these problems by quite a bit were it not for the fact that perfluorocarbon is about twice as dense as water.

 

[cragar]

so if i strapped an air mattress to me, filled with nitrogen and got submerged in the tank and then accelerated up i would move forward in the tank correct. Just like when you have a helium filled balloon in a car and you hammer the gas, the balloon moves forward in the car.