For example in Top Gun Maverick when they have to do the high climb, or in Interstellar in the docking scene what’s happening to their bodies. Also what is the difference between postive and negative g’s?
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G. Refers to acceleration which is related in terms of earth’s gravity 1 g = 1 earth gravity.
4g = 4 x earth gravity (9.81 meters per second^2)
G force is the push/pull effect on your body relative to the natural gravitational pull on your body.
Positive g-force is acceleration of your body against gravity’s pull – think about being on a roller coaster going uphill really fast. This is the feeling that your stomach is still at the bottom of the hill but your body is going up.
Negative Gs is the opposite – your body is falling faster then the natural gravitational pull. Now you are at the top of the roller coaster going down – the feeling that your stomach is still at the top while you are moving down rapidly.
The reason this is critical to monitor for pilots and such, as they point out in top gun, is that excessive G forces can cause your blood pressure to drop and your brain to lose oxygen from lack of blood flow. The blood pressure drops, because the pull is so strong that the blood cannot flow properly.
G = the force of gravity. Two positive G’s means that everything in the plane is feeling twice the normal effect of gravity. Negative G’s is the opposite, it means that everything is feeling an upward force instead of downward.
Positive G’s are easier for the body and airframes to handle, though special care has to be taken to ensure the pilot doesn’t pass out from lack of oxygen to the brain. Pilots are trained to clench muscles in the lower body during high G maneuvers to keep blood from draining to their legs. There are also suits that they can wear that do this automatically.
You can feel the effects of both positive and negative G’s by going over a hump in the road at a high rate of speed. When you hit the hump, you will feel positive G force as the car is lifted up from underneath you. Then you will feel negative G as the car falls back down and pulls you with it. Lastly, you’ll feel positive G’s again at the moment the car settles back down. These will only be very minor changes from what your body is used to feeling (1G). A fighter pilot will regularly be flying maneuvers that reach 8 G’s or even more. That means a 180lb pilot will feel like he weighs over 1400lbs. You can also multiply the weight of the airplane by 8 and see what kind of forces the airframe must be built to handle.
G-Force (The G stands for gravity) is a measurement of acceleration. 1 G is the amount of force you feel the earth’s gravitational force pulling on your body at rest. But G-forces are used to also measure the force you feel when your body is accelerating (positive) or decelerating (negative). It’s caused by the mass of your body being exerted against the positive or negative acceleration. You feel a mild version of G-forces as you drive around in a car. But most normal driving only produces about -0.1g on braking and +0.1g on acceleration. Some pilots experience extreme G-forces when doing maneuvers and the maximum amount they can endure is around 18 G’s.
When you’re in a car (or plane, or spaceship, or roller coaster) and it speeds up, it feels like something’s pushing you back into your seat. What’s actually happening is the opposite: The car — frame, seats, etc. — speeds up before you do, so the seat pushes on you.
Usually force is measured in Newtons or pounds. But in this case we instead measure it relative to the force we normally feel from Earth gravity. So for example, 3 G’s is an amount of force 3 times as strong as normal gravity.
The human body isn’t a single solid lump. The same logic applies to your internal parts. When you’re accelerating, your bones and flesh speed up first, which means your blood squishes in the direction of acceleration. If it’s only a little bit of force, your heart has no problem pumping your blood back to where it should be. But a normal heart isn’t strong enough to get blood to your brain around 5 G’s; so most people black out somewhere around that amount of force. (And obviously if your brain has no blood for more than a minute or two, you’ll be dead or permanently brain damaged.)
Negative G’s is when the acceleration is in the opposite direction (for example hard braking, or a sudden stop). Instead of experiencing a force pushing you into your seat, instead you experience a force pushing you out.
Again, what’s actually happening is the opposite of what you feel. With negative G’s, you’re thrown forward because the car’s slowing down, but you’re not.
(Negative G’s are why roller coasters have forward restraints and cars have seat belts. To stay safe, you need something that will push you backwards in a controlled way as the vehicle is slowing down. A car stopping immediately — for example running to a wall at high speed in a bad car accident — is an instant spike of very high G force, like tens of G’s. Again, you’re not a solid lump, you have a bunch of different stuff inside you. In this case the force is so strong your organs ram against each other causing invisible internal injuries. Which is why a seatbelt is an elastic restraint, it slowly ramps up the backward force as you continue moving forward, which hopefully reduces or eliminates injuries by bringing you to a slightly-less-sudden stop.)
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