Why are the Actual G Forces Experienced by Astronauts Less than Predicted?

[ultimateroxas]

Homework Statement

why are the actual g forces astronauts experience are less than those predicted.

Homework Equations

The Attempt at a Solution

Many internet searches
Textbook study

 

[ShawnD]

Which G forces? Takeoff? In space? Reentry?
And do you have a number for what the predicted gravity should be?

 

[ultimateroxas]

I'm pretty sure it's from takeoff
and the gravity should be 9.8

 

[ShawnD]

That 9.8 only applies to things that are moving at a constant speed. Right now I'm sitting in a chair and my velocity in an up/down direction is a constant 0, so gravity is the only thing acting on me. The shuttle has more "gravity" force because the shuttle is accelerating in an updward direction. The Earth's 9.8 gravity still applies, but on top of that you need to add the force caused by shuttle acceleration. F=ma.

In case that sounded weird, 9.8m/s^2 only applies on earth. F=ma applies to everything in the universe.