Am I the only one who ever thinks about countering g-forces by allowing a pilot to be submersed in liquid instead with neutral boyancy. This would completely eliminate passing out from g-forces at any acceleration factor.

Though of course it would be complicated so I understand why it isnt done. You would need a complicated system to maintain pressure in the tank so it wont fluctuate quickly. But since g-forces are usually transient if done correctly decompression might not be a big issue

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@freemo liquid weighs a lot, plains need to weigh as little as possible :notears:

@Ccrack like i said, I dont think it is practical.. Only that I think about it a lot :)

@freemo hmm are you thinking planes here or would this also work on space flight ?

@zleapin theory either could work. In practice im not sure if it would be practical in either situation. Simply because im not sure it would be practical on a plane, despite it being more useful.. Are getting higher g-forces even important to space flight. Seems we can do most of our acceleration slowly on a space craft. Though would be much easier to implement on a space ship.

@freemo I'm pretty sure you would still feel a lot in body where there is still air.

@freemo that's the idea behind the g-suit:

It directs fluid to bladders around the lower body to counteract the ฯgh gradient the pilot's blood is subjected to, which means that pooling blood in the legs doesn't represent a low-energy state, which in turn means that blood has less tendency to leave the brain and impair function.

@khird yes, im aware.. but if the pilot were completely emersed in water then there would be absolutely no effect from g-forces in that fashion. Any increase in g-forces would present as if the person just was deeper under the water than they are (like a diver)... So at any g-force the the pilot would be immune from passing out (though you'd have to deal with the pressure changes now)

@freemo well, not exactly. Going deeper underwater changes the gauge pressure a diver observes, but not the hydrostatic pressure difference between his head and his toes (ฮ”P=ฯgฮ”h). ฯ and g are effectively constant no matter where the diver is, and ฮ”h is just a function of his posture - his height, if he stands upright.

But for the pilot in a non-inertial reference frame, g is not constant. So when he manouevres, the ฮ”P changes substantially, while the diver will always see about 17.8kPa (182cm diver standing upright in freshwater) higher pressure at his toes than at his head if standing upright.

I am aware of that. But when a pikot is neutrally boyant underwater he does not expiernces what a pilot outside of water expiernces. It woukd be indistingushable to a higher oressure on the liquid.

The imbalance you suggests is specifically due to being negatively boyant in air. The same way a centeifuge cant seperate out anything that is neutrally boyant either.

Ok so yea there would be a pressure gradient that is steeper than usual in the water, your right. Meaning for it to work the tank would need a higher than normal pressure applied since fradient becomes less at depth.

@freemo sorry, what gradient becomes less at depth? dP/dh = ฯg no matter what depth h you have.

@khird lets say your 6.6 feet tall and in a tank of equal height. At rest you have 1 ATM at the head and 1.2 ATM at your feet. If you accelerate at 10G that would be 1ATM and 3 ATM, so your feet have 3x the pressure at your feat relative to your head.

However if the tank was at 10 ATM then at res you have 10 ATM at the head and 10.2 ATM at rest at your feet but when accelerating at 10g you would expiernce 10 ATM at the head and 13 ATM at your feet, which is 1/1th the pressure difference at only 0.3x the difference between head and feet.

@khird So the more I think about it you might be right. while at pressure the ratio of pressure difference between head and feet would be much smaller the absolute difference would be the same. I think its the absolute difference that would matter.

With that said it only applies if you are standing verticle. If you are neutrally boyant the pressure gradient should cause you to be pushed horizontally. Thus the pressure gradient would be much less and the difference would be between the front of your body and the back.

I dont think that would be much better though and as you suggest it might not solve anything.

Isn't this a common trope in SF? Even Neon Genesis Evangelion uses it.

@freemo at a point you would have the same problem tho, right? A much higher point, but still. That would be a cool experiment, I wonder how much you could increase before same result? 5x? I will let you take care of the funding :ablobcool:

@freemo Are we sure that this would work? Thinking back to physics class, it seems to me that your ship, the liquid, and you all are subject to the same might not hit the wall, but wouldn't your internals still suffer the same stresses?

@freemo I have been thinking about this in the past and the idea is not new (Event Horizon from 1997? uses this mechanic).

Besides adding a ton of extra weight to the airframe (baaaad) you would still have to deal with brains getting put under server pressure, blood draining from the brains and the ability to move your limbs in case its needed.

This how ever can be mitigated by flying a bird remotely. EW becomes a thing, latency, airframes not being able to handle high-G loads, equipment on hardpoints unable to handle the Gs It is prolly cheaper to have like 500 drones with explosives swarm your target and zerg-rush the fuck out of it.

@xyfdi Well no. You wouldnt expiernce pressure on the brain.

As we discussed when under water in a 6.6 foot tank at 10 ATM pressure when at rest if you go 10G and were standing straight up there is only 0.3x more pressure on your head than feet. If you are lying perpendicular to the direction you move it is negligable.

You dont have the same effect of blood rushingout of your head as you would if you were out of water because the G force is translated into a somewhat uniform pressure with a much smaller difference across the body than what would be expiernced in air.

It would be no different than what a scuba diver expiernces at depth, except with a slightly stronger gradient.

@freemo ( tired AF, longform no go ) Has this thing with the tank been tested somewhere?

@xyfdi I dont honestly know.

As I said at the get go I dont expect it to be practical enough to actually put into use in any sorts of aicraft we use today or maybe not even in the future. It is more a curious thought experiment than an actual solution in my mind.

@freemo I think about it a fair amount to be honest. When you think about it, the pilot is already submerged in a fluid. We just have to consider how the pilot is supported. Changing that fluid and working out how something will move in it would take some research but it could be interesting.

I think a problem that is always going to be there is the way that the human body works internally. Our organs will move independently, no matter how we might be supported in space. Our brain can be concussed quite easily if we are jolted. Working out how to stabilise our internal structure for that kind of travel would be quite the challenge I think.

@Nyoei The medium matters more than you think. The reason your brain pushes towards the back of your skull is specifically because you are supported in a chair, which exhibits a counter force.

Consider a person in a falling elevator, they expiernce weightlessness and their internal organs behave as if weightless as well. Yet they are accelerating at 1G. Meanwhile someone on the surface of the earth expiernes their internal organs being "crushed" by that same 1G force, although that crushing is well within tolerance.

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