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# Orbital physics broken? or only bad?

## Question

Hello!

i have a strange problem... i heard only good stuff about the game physic in KSP. But the following is just strange...

Im playing Version 1.7.3.2594 on linux

At the moment i am playing the trainings.

In the mission "Return from Mun" my vessel makes an over 90 degree turn when it switches to the Kerbin orbit...
I made pictures but that the forum wont let me upload the pictures...

My understanding of physic would be that, when i am escaping the moon in the opposite direction of the moon and in direction between Mun and Kerbin to approach kerbin from the left side... (turned away from mun)

I hope i explained it clear enough

is this training somehow scripted? or is there some switch for realistic physics?

## Recommended Posts

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You're probably getting thrown off by the relative motions when the SOI switches. In the Mun's SOI, you're going in one direction (and the Mun is stationary). However, the Mun itself is moving relative to Kerbin, so when you switched to Kerbin's SOI, it looked like you're going a different direction. You were going that direction before the switch too.

Edited by Empiro

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i just started from Mun again and then switched to Kerbin as viewpoint... then i saw the real path...

the most important thing that i realized is that the drawn path are relative to the corresponding Object. So the 90 degree turn wasn't a turn at all^^

So no bad physic just misinterpreted paths...

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In order to be approaching Kerbin from the left had side you'd have to burn longer to completely kill your orbital speed and then add retrograde speed to raise your periapsis again. You can think of the situation without the Mun at all. You're in a high circular orbit and you burn retrograde to lower your periapsis. It doesn't put you in a retrograde Kerbin orbit it just makes it more elliptical.

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Welcome to the forums.

Just to repeat what the others have said already -- your Navball does not show absolute coordinates. The coordinates are relative to the surface of whatever celestial body's Sphere of Influence that you are in.

"East" for the Mun is in a completely different direction than East for Kerbin, almost all the time. And as you move along your orbits, things like "radial out" end up pointing in completely different directions for the Mun, or for Kerbin. You can see on your map that there is a marker to show the moment you change from being in the Mun's SOI, to being in Kerbin's SOI. At that moment, your navball will completely change direction from being in a Mun-relative coordinate system, to being in a Kerbin-relative coordinate system.

This is almost certainly what you are seeing. The physics in KSP is very good.

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Physics is good, but I've seen the occasional SoI transition error.  I'd basically hit the SoI and "bounce" and have to spend a LOT of dV to fix my path.

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6 hours ago, Kryxal said:

Physics is good, but I've seen the occasional SoI transition error.  I'd basically hit the SoI and "bounce" and have to spend a LOT of dV to fix my path.

Without time warp? That’s usually what inroduces the error.

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On 8/26/2019 at 4:33 PM, MadMe86 said:

I made pictures but that the forum wont let me upload the pictures...

Upload them to a free image service. I use Imgur myself. Then you can get the url to the image and link to that here.

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