Liquid as counter to G-Forces

kojikun · Post by **kojikun** » 2003-05-02 12:04am

I've seen bits and pieces about using a liquid such as water as a way to protect a person against the side effects of high-g acceleration, namely being squashed to little bits.

I understand that because of buoyancy you would remain floating on top of the water, but at high accelerations/decelerations, water is about as hard as concrete. So how does it benefit you? Is it because youre not going from free-fall-to-acceleration very rapidly? because i don't see a difference.

any links to websites would be great. im not sure what to type into google, so im getting bad results.

Post by **weemadando** » 2003-05-02 12:05am

Apply force to liquid and you get pressure.

Liquid will not ever buffer G-forces it will just result in a whole new set of issues.

kojikun · Post by **kojikun** » 2003-05-02 12:10am

thats exactly what i was thinking, but i keep seeing people talking about using liquids as the miracle "anti-g-force" cushion for futuristic high acceleration fighters and shit. I don't get it.

maybe its meant to count blood pooling, but thats silly because g-suits already do that, theres no point in adding a tonne of water just for anti-pooling when a lightweight suit will work just as well.

Hobbes · Post by **Hobbes** » 2003-05-02 12:17am

kojikun wrote:thats exactly what i was thinking, but i keep seeing people talking about using liquids as the miracle "anti-g-force" cushion for futuristic high acceleration fighters and shit. I don't get it.

maybe its meant to count blood pooling, but thats silly because g-suits already do that, theres no point in adding a tonne of water just for anti-pooling when a lightweight suit will work just as well.

Pressurised flight suits have been used as counter to G forces, but sitting in a tub of liquid making a high-G turn you're going to get the same problems as if you just went from the surface to 30m of water and back to the surface in the space of a few seconds. Which let me tell you, is not going to be good.

*edit* - this is WeeMadAndo talking, just using a different account. I'd forgotten. Shit.

Exonerate · Post by **Exonerate** » 2003-05-02 01:29am

Now we know who that sock puppet was.

Faram · Post by **Faram** » 2003-05-02 04:46am

Woot a NOOB

*POKE*

Post by **Sea Skimmer** » 2003-05-02 04:54am

Faram wrote:Woot a NOOB

*POKE*

Hobbes wrote:*edit* - this is WeeMadAndo talking, just using a different account. I'd forgotten. Shit.

Messon · Post by **Messon** » 2003-05-02 07:27am

http://www.ngb.army.mil/news/2000/11/14/anti-g.shtml

http://campus.umr.edu/maeem/events/news ... ysuits.htm

http://dustbunny.physics.indiana.edu/~d ... /NYT6.html

Here are a few links I found in a hurried Google search. Not sure if it's what your looking for, though. I had to wade through about 20 pages.

kojikun · Post by **kojikun** » 2003-05-02 09:34am

thanks, but i already knew that anti-g suits were used (the medium was irrelevant).

what i was talking about was the idea of sticking someone in a tank of water and they'll be able to take high-g turns no problem. the whole idea made no sense to me.

Sebastin · Post by **Sebastin** » 2003-05-02 10:17am

Actualy liquid can help a lot.

The german airforce has a anti g suit in the evualation phase that works by simply having a liquid layer around the pilot and is totally passive otherwise. Sort of just being a wearable tank.

They are getting spectecular results, IF I recall correctly pilots being fully responsive to 12G and conscious to 16G. Might be wrong though.

I´ll try to dig up my source.

German project name is "Libelle" if you want to search yourself.

Alferd Packer · Post by **Alferd Packer** » 2003-05-02 11:42am

What about total immersion in liquid? Like, say, put fish in an immensely tough tank and fill it completely with water, and then drop it from a building. Would you encounter similar pressure problems?

Durandal · Post by **Durandal** » 2003-05-02 02:27pm

Alferd Packer wrote:What about total immersion in liquid? Like, say, put fish in an immensely tough tank and fill it completely with water, and then drop it from a building. Would you encounter similar pressure problems?

Fluid dynamics makes my brain hurt.

Messon · Post by **Messon** » 2003-05-02 03:54pm

http://www.hq.nasa.gov/office/pao/Histo ... /ch2-4.htm

According to that site it seems that R. Flanagan Gray was the first to use submersion in water to reduce the effect of g-forces. He lasted up to 31.25g. So far I haven't been able to find any more out.

kojikun · Post by **kojikun** » 2003-05-02 07:46pm

how the hell did that work? i dont see why being submersed in water is any help at all.

GonK · Post by **GonK** » 2003-05-02 09:19pm

If I'm understanding the bits and pieces I've read then immersion in water wouldn't be a practical solution to allow peole to survive rapid changes in G forces. Simply put the system is just too heavy and would have far too much momentum to allow for any rapid changes in acceleration.

What it does seem to be very good for is if you are dealing with a gradual build of forces in which case I would think that the water would act as a very efficient G-suit, appling equal pressure to the whole body as well as damping out any vibrations from the rocket, and in the event of any impact the water will absorb alot of the forces.

The problem with any water immersion system will be breathing. The air supply would have to be pressurised and very carefully controlled otherwise whoevers immersed will just end up sufferung from the bends exactly the same as divers when they surface too quickly.

kojikun · Post by **kojikun** » 2003-05-02 09:57pm

you sure its necessary to completely submerge the person? couldnt you just have them float in a tank of water? they have the same buoyancy and everything. I think that would be necessary, actually, because a fully enclosed tank with no air would result in the person getting crushed against the tank in the direction of acceleration!

EmperorChrostas the Cruel · Post by **EmperorChrostas the Cruel** » 2003-05-02 11:24pm

Would the property of buoyency help against G forces? Being in water makes you weigh less, (but mass the same) so would this apply to G forces as well?
Edit, once again, too slow typing!

kojikun · Post by **kojikun** » 2003-05-03 12:30am

it wouldnt help, because the water still has to push you up. and accelerating at the same rate as the water doesnt cushion you, it just makes both heavier. sufficiently high accelerations would be like landing flat out on open water after jumping from a height of 30 metres. You = SPLAT

The only real benefit i can see is automatic pressure to counter the blood drain issue, but its not worth the cost when suits work well enough and dont require massive rethinking of cockpit design.

Post by **weemadando** » 2003-05-03 01:27am

How much more do I have to explain this - using fluids as a buffer to g-forces is a fucking stupid idea.

Sebastin · Post by **Sebastin** » 2003-05-03 04:17pm

weemadando wrote:How much more do I have to explain this - using fluids as a buffer to g-forces is a fucking stupid idea.

Neither the german nor the us airforce seem to agree with that assessment.

I found this: http://www.sciam.com/article.cfm?articl ... 9EC588EEDF with a quick search for Libelle. just skimmed it, didn´t have time.

I remembered that my original source was offline (Article in Spektrum der Wissenschaft), don´t know if i can find it. IIRC they cut the amount of liquid needed to less than 2 liters during development, the suit is not more unwieldly than a normal g-suit.

kojikun · Post by **kojikun** » 2003-05-03 10:39pm

sebastin, thats NOT what we're talking about. Thats a SUIT where the AIR is replaced with WATER.

We're talking about a TANK you SIT IN.

Post by **weemadando** » 2003-05-03 10:41pm

Sebastin wrote: I remembered that my original source was offline (Article in Spektrum der Wissenschaft), don´t know if i can find it. IIRC they cut the amount of liquid needed to less than 2 liters during development, the suit is not more unwieldly than a normal g-suit.

Different concept. This is using liquid under pressure as part of a flight suit to maintain blood flow to the head. Not using a pilot in a freaking tub of liquid that supposedly will act as a buffer to G-force.

NapoleonGH · Post by **NapoleonGH** » 2003-05-04 01:20pm

weemadando, what about that guy who the link is for up a few posts saying that he survived and was conscious for 32 Gs? if that is the case, it would be excelent for a ship that is trying to accelerate to near reletivistic speeds for interstellar travel.

BTW is it just me or is the concept of reletivistic speeds pretty d*mned convenient. You want to go somewhere 50 light years out, normally would take say 53 years to get there at near C velocities, but here comes reletivity makinng it take those 53 years as far as the outside world is concerned, but the person within the ship only has to deal with a few years/months of time from their point of view. Seems pretty convenient to me.

Sebastin · Post by **Sebastin** » 2003-05-04 05:15pm

I understand that you are talking about putting the pilot in a tank. My point is that it would work. A body fully submerged in liquid will not experience g forces if the liquid has the same density as the body, which roughly works out for humans and water. It also works for partial submersion, with only the non submerged parts still experiencing forces. That´s the way I understand it at least. IIRC the point was that liquids are not compressible. I don´t understand the exact workings though.

An experiment would be to put a completly filled water baloon in a water filled, sealed glass and swirl it around. The baloon should not be pushed out by the centrifugal force. (I just had this idea, so ... well. Let´s just say I could be horribly off here.)

The thing about the suit was that:

1. The article was where I first read about the above outlined principle, so it immediatly came to my mind.

2. It is an actual application of this exact principle. It is NOT just a g-suit using a different medium. It works by "submerging" the pilot in liquid without any active control. It just does so in a convienient package. It´s, as I said, a wearable tank.

3. Since the point was to protect an airplane/spaceship/whatever pilot I thought a real world example would be apreciated.

PS: I didn´t ponder it before writing this post, but the more I think about it, the point about the body and the liquid medium having the same density seems to be the cornerstone of making this work.

kojikun · Post by **kojikun** » 2003-05-04 07:58pm

NapoleonGH wrote:BTW is it just me or is the concept of reletivistic speeds pretty d*mned convenient. You want to go somewhere 50 light years out, normally would take say 53 years to get there at near C velocities, but here comes reletivity makinng it take those 53 years as far as the outside world is concerned, but the person within the ship only has to deal with a few years/months of time from their point of view. Seems pretty convenient to me.

Convenient, until you arrive at your destination and realise two wars have turned it to shit, your property has been reclaimed, etc.

Fuck, if youre lister you could leave a penny in a bank account and make a bajillion dollars from interest, leave your bathroom light on and owe the power company half your savings, and leave a halfeaten sausage out and turn half the planet into a mold covered lump!

The problems are too big. Everything has to be run by lawyers or bankers for things to last over the long times. And worst of all, if you leave someone behind, they'll be dead before you get to your destination. You cant have any friends unless they either do the same, or are with you.

But one benefit is that you get to see history make itself. Travelling at 99PSL for a few decades, then staying out for a year or two, and you'll live for a few thousand years!