this post was submitted on 13 Sep 2024
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Science Memes

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submitted 1 month ago by [email protected] to c/[email protected]
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[–] [email protected] 8 points 1 month ago* (last edited 1 month ago) (2 children)

Why would you need to entirely cancel the earths orbital velocity, surely you just need to cancel a ~~tiny~~ bit of orbital velocity?

Edit: https://space.stackexchange.com/questions/43913/do-you-need-0-km-s-velocity-to-crash-into-the-sun

[–] [email protected] 13 points 1 month ago

Canceling out only a tiny bit puts you on an orbit similar to earth's. You need to kill basically all of your momentum.

[–] [email protected] 10 points 1 month ago (1 children)

Good question, but if you cancel out only a little bit of orbital velocity, you just orbit in a little bit closer. Without any appreciable drag acting on you, there's nothing that will keep your orbit decaying. You'll just be in a smaller, perhaps slightly more eccentric orbit.

[–] [email protected] 0 points 1 month ago (1 children)

But you'd need a higher velocity to orbit closer...

[–] [email protected] 1 points 1 month ago

Yeah, orbital mechanics gets a little bit mind-bendy sometimes. If you're in a stable circular orbit, accelerating in the direction you're traveling will actually result in you traveling more slowly because you have moved to a higher orbit, and firing engines to slow down will actually speed you up because you move in closer to the host body and take up a faster orbit.

This is actually a problem spacecraft deal with regularly. If a Dragon capsule is behind the ISS and wants to dock, using its thrusters to accelerate toward the ISS will actually result in it falling further behind. Decelerating will get it closer, though it will then be in a lower orbit. Orbital rendezvous is tough.