OK, this is dumb, but it's gone through my head a couple times. I've seen a few science fiction movies and shows where the people in the spaceship use a gravity assist and lean into the turns like they're driving NASCAR or riding a roller coaster.
I think they wouldn't feel the acceleration (vector change) because gravity is doing the acceleration on every molecule and there would be nothing to lean against. I'm often wrong though. Someone smarter than I am have some insight?
EDIT: For what it's worth, I guess I shouldn't have used the Expanse clip as it upset some people. I just used it for an example of what I was asking. The question is this: Under little or no thrusters, would you feel a gravity assist? Even a radical one that changes your direction 90 degrees and greatly increases your velocity?
You're correct in that he would not feel anything from the assist itself, as the spacecraft is accelerating the same amount as him. However, the key here is that he appears to be dramatically altering his attitude with some kind of RCS thrusters. There's not much use to that unless he's firing the main engine, but I'm assuming no main engines were used as they don't appear to ignite.
The leaning appears to be in response to attitude corrections, and is pretty accurate given the rate of rotation here. The way he's bracing only makes sense in gravity, so I'll assume the ship has an AG field (like most standard sci-fi ships).
The only thing that appears to be off its the acceleration at the end …
No anti-grav in the expanse.
I read that scene as him feeling the flow of the ship as they time the gravity assist with minimal thrust since the point of that scene was to run quiet.
The leaning could also even just be that thing gamers do when we lean into a turn in the game by actually leaning in our seat.