What will be the impact of 9+ g on normal person's body. How does it feel?
Normal is 1g, meaning as is in your everyday life activities.
In the US, there are roller coaster rides that will give you up to 3g, maybe a bit higher, and there are a lot of people who got sick at 2g.
Space Shuttle launches are 4-5g.
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Why don’t the pilots wear G-suits?
G-suits are designed with air bladders (pockets) that inflate and deflate to keep a pilot’s blood from pooling in the pilots’ legs while executing sharp, unpredicted combat maneuvers. Unlike combat flying, the Blue Angels demonstration pilots know the maneuvers they will fly prior to execution, so each pilot knows when one will be pulling heavy gravitational forces. Anticipating the changes in gravitational forces allows the Blue Angels demonstration pilots to combat the G-forces with muscle contractions. In addition, the Boeing F/A-18’s control stick is mounted between the pilot’s legs. The Blue Angels have a spring tensioned with 35 pounds of pressure installed on the control stick that gives the pilot a “false feel.” This allows the pilot minimal room for uncommanded movement. The pilots rest their right arms on their thighs for support and stability while flying. Therefore, inflating and deflating air bladders in a G-suit would interrupt this support and stability, causing uncommanded aircraft movement. In this case, G-suits would detrimentally impact flight safety.
An inexperienced person can withstand up to about 5g with no g-suit. At about 6g and sustained, the person would begins to black out, aka G-LOC (loss of consciousness).
Yeah...I know what that feels like.
On the other hand, a trained pilot, like the Blue Angels guys, can withstand 6+ with no g-suit, and supposedly the Blue Angels and T-birds guys can withstand 9g for short periods, like how they fly in airshows.
The g-suit is to help you being conscious and with sufficient awareness at sustained 9g, but there are still physical effects. It is difficult to explain but to start with vision, my vision began to go dark grey at the the edges, then got progressively larger towards the center. The analogy is like looking into a tube that gets smaller and smaller. So while I was conscious, my vision was effectively worthless.
Body-wise, it got progressively more difficult to breath. Not a problem up to 4g and most people could handle that. But past 4g and I had to make conscious extra efforts to breath. The g-suit was not there to help me breath but to prevent rapid blood escape from my upper body. Past 6g and I had to strain to breath, also at higher than 6g, it was very difficult to lift any limb. Not impossible, just required a lot of muscle effort, like working out in the gym. At 9g, forget about large movements. Just turning my head was straining the neck muscles.
At 9g, it is not about any physical damages but about consciousness and situational awareness. Different bodies will have different responses. When I went from the F-111 to the F-16, the reclined seat in the F-16 definitely produced better g-tolerance than in the F-111. On the other hand, I know F-111 guys who are physically larger than me and reported no differences at all. Larger, not necessarily taller. In g-force tolerance, a stockier physique tends to produce better tolerance levels.