What is the highest G-Force a human can take?

G-Force, the force of gravity an object has on it, whether in acceleration or because of gravity pulling on it. We currently live in a 1 G (measurement of G-force pull) on this earth.
A zero g-force would be zero force pulling on us or the object at all....we would therefore float without any influence or force on the body.

To understand simply, when a person breaks hard in a car, the pull you have on your body when stopping is the g-force you are feeling on the body as the seat and hopefully the seat-belt pull you back with the car.
the same is experienced on a roller-coaster ride in the sharp corners.

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Human body issues with G-Force

We have a blood needy brain and body! This is also our biggest issue with high g-force. When the body is experiencing head to toe g-force, as in the pull is downwards towards our feet, then the heart has to work really hard to get the needed blood to the brain.
Without this blood, the needed oxygen would affect the brain and body in many ways. From loss of vision hue (grey out), to tunnel vision, blackouts while still awake (complete loss of vision), loss of consciousness and even eventually death!
They say that >5G is already too much for the hearts ability to keep up with the pressures to feed the brain.

Even though side to side is not as bad as head to toe g-force for us, remember we are made up of mostly water and is essentially soft, and this means that as the g-force increases, you body can take only so much stress and then issues start to happen.

• broken bones
• organs shifting
• blood vessels bursting
• internal bleeding

Toe to head G-force is even worse than Head to toe G-force. At more than -3G the blood floods into the head causing the face to swell up and your lower eyelids are forced over your eyes. This is called a ‘redout’ because of the red light you see shining through your eyelids. At -3g, your blood also can't return to your lungs and you will quickly pass out and die as well.
HECTIC!!

They do have G-suits to help keep the blood in the areas the body needs it. Pilots use these suits to push the blood from their legs into the head where it is needed during high G turns.

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What G-Force is dangerous then?

This is a difficult question to answer because it depends on how long you experience the high G-force. Lets say you starve the head from oxygen for a half a second...no problem. Do that for 10 minutes and you have a very different picture!
For example there is a rollercoaster with the highest G-force that gets to 6.3G. BUT because this is only a few seconds this is not a big problem.
Fighter pilots have those suits to allow them to experience G's of 8 or 9 G's, but this is also only for a few seconds at a time, or they would pass out and eventually pass away.

One guy even thought this would be a great way of euthanasing people! Seriously, I mean check this guy out!

There have been cases where humans have experienced high G's for a very short period of time. Like in the 50's when a chap agreed to test a rocket sled and experienced 50-60G's for a short period of time which caused damage to the eyes and body.

And F-18 pilot struck the ground and had extremely high G-force for a second of up to 75G's. he is now 3 inches shorter than before and suffered broken bones through his face, body and extremities during that high G incident.

So for most people this probably would have been fatal, but he being a trained and fit person pulled through. Most wouldn't.

In fact high G's and the ability to withstand it is relative also to the fitness of the body. If the heart is stronger they would be able to withstand the pressure of getting the blood to the right place in most cases.

So to answer my own question, this is very relative to the situation, length of time, fitness and direction of the G-force. One cannot say it is >10G....it just isn't a line in the sand.
But some fun below on the subject matter.

Steve are you with me? LOL!!!

Perfect example of no blood to the brain!!

I would love to try this out for the experience of it.

A compilation of G-force craziness :) ENJOY

[Image and info credit is travel.thefuntimesguide.com, YouTube]