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Effect of a gravity assist on person, or whatever, in spaceship (sopuli.xyz)

submitted 1 year ago* (last edited 1 year ago) by [email protected] to c/[email protected]

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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?

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[–] [email protected] 3 points 1 year ago

It depends on how strong the gravity source is and how close you get to it. The strength of gravity falls off with distance following the inverse-square law, so different parts of your spaceship can feel different amounts of force acting on them during the manoeuvre. In the clip, there's a large but weak source of gravity (a moon), so I don't know how much force the pilot's going to feel - probably less than he feels because the ship is rotating and generating centrifugal force.

But we've got a pretty good example of what I'm talking about over our heads - Earth's moon is in orbit around us. You could think of that as a gravitational assist manoeuvre that never ends because the moon didn't gain enough speed to break free of Earth's gravity. Over a time scale of billions of years, the difference between the gravitational force exerted on the near side and the far side is causing the moon's rotation to slow down.

For a fictional example that makes it clearer, Larry Niven wrote a story in 1968 titled "There Is A Tide" in which a pilot has a close encounter with a neutron star.