this post was submitted on 02 Oct 2023
50 points (90.3% liked)

Ask Lemmy

26778 readers
2546 users here now

A Fediverse community for open-ended, thought provoking questions

Please don't post about US Politics. If you need to do this, try [email protected]


Rules: (interactive)


1) Be nice and; have funDoxxing, trolling, sealioning, racism, and toxicity are not welcomed in AskLemmy. Remember what your mother said: if you can't say something nice, don't say anything at all. In addition, the site-wide Lemmy.world terms of service also apply here. Please familiarize yourself with them


2) All posts must end with a '?'This is sort of like Jeopardy. Please phrase all post titles in the form of a proper question ending with ?


3) No spamPlease do not flood the community with nonsense. Actual suspected spammers will be banned on site. No astroturfing.


4) NSFW is okay, within reasonJust remember to tag posts with either a content warning or a [NSFW] tag. Overtly sexual posts are not allowed, please direct them to either [email protected] or [email protected]. NSFW comments should be restricted to posts tagged [NSFW].


5) This is not a support community.
It is not a place for 'how do I?', type questions. If you have any questions regarding the site itself or would like to report a community, please direct them to Lemmy.world Support or email [email protected]. For other questions check our partnered communities list, or use the search function.


Reminder: The terms of service apply here too.

Partnered Communities:

Tech Support

No Stupid Questions

You Should Know

Reddit

Jokes

Ask Ouija


Logo design credit goes to: tubbadu


founded 1 year ago
MODERATORS
 

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 are viewing a single comment's thread
view the rest of the comments
[–] [email protected] -4 points 1 year ago* (last edited 1 year ago) (3 children)

Gravity is why people lean into turns in the first place.

Those molecules have velocity that's taking them past whatever body they're using for a gravity assist. The gravity of that body grabs the vessel and begins to pull it in, being pulled closer to the body generating that acceleration and not simply passing by. The previous vector doesn't just disappear. All that matters still wants to continue in that direction of travel, including the people. The result is people having to lean into the arc of the assist because their own momentum is still changing to the new vector.

In short. Inertia is a bitch

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago)

I am not so sure.

In a gravity assist ( to be technical using a hyperbolic orbit of a large mass to change direction and gain velocity) the object is still following the curvature of space time. So the change in direction is affecting all particles in the object at the same time. There is no external force involve, so inertia does not come into play.

It is the same as people in the ISS orbiting the earth, they do not have to lean in the curve as they are following the curvature in spacetime around the planet. The only difference is one is a hyperbolic orbit (gravity assist) while the other is a ~~parabolic~~ elliptical orbit (ISS)

While the analogy the OP used of leaning into a turn is changing direction and there is a force that is only acting on part of the object (the tires of a car or motorbike).

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

Only one problem - the relative velocity of the ship is the same. Yes, the ship's vector got changed, but yours did too. Same reason you don't feel centripetal force in orbit, despite the constant vector change at 9.8m/s^2...

[–] [email protected] 2 points 1 year ago

There is a miniscule amount of tidal forces felt during a gravity assist. Ultimately, the spacecraft and it's cargo are in freefall. The gravity assist would be barely noticeable. Remember that gravity isn't a "force" it's a bending of space changing the direction of a "straight " path. The spacecraft is traveling in a straight line with no other forces acting on it. The space that straight line is passing through is bent around the mass providing the gravity assist.