– Why do people pass out when subjected to high g-forces?


– Why do people pass out when subjected to high g-forces?

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Large G-forces tend to squeeze blood towards one end of the body, preventing it from circulating normally and depriving the brain of oxygen. Reduced oxygen supply to the brain results in tunnel vision, blackouts, and loss of consciousness.


Heart pumps blood
Blood goes up arteries to brain
High g forces stops this by making blood weigh too much for normal pressure to work
Brain gets no blood and shuts down
Beep boop beep, dead/pass out

Your brain is high up in the body. When G-forces are strong, it literally pulls the blood downwards through your body and blood is literally taken away from the brain. You pass out – hopefully temporarily – from oxygen deprivation since there’s no blood carrying oxygen reaching the brain for a little while.

Suits can pressurize around your lower body, preventing the blood from pooling down there, basically squeezing it back upwards, and giving you a much better chance at staying awake.

The heart is only so strong. It is used to pumping blood that weighs roughly 1 Kg per liter. At 9G, blood weights an equivalent of 9 Kg per liter. Under such conditions, without assistance the heart simply isn’t strong enough to pump enough blood out from the legs and lower abdomen to the brain in order to sustain consciousness.

When oxygen doesn’t reach your brain you pass out very quickly. First your hearing and vision goes away and then you pass out. When subjected to high G forces it messes with our blood circulation. It often pushes your blood out of your head. Our heart just can’t produce the required blood pressure to counteract the acceleration. So no blood reaches your brain therefore no fresh oxygen and the brain stops to function. Spend around 2 minutes without oxygen reaching your brain and you are dead.