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# Is craft orientation reference frame rotating around celestial north-south axis?

## Question

I always thought that when in space on SAS or on warp the craft will keep it's direction with respect to the celestial sphere (skybox) just as all the orbits do. But recently I noticed something odd.

When I'm in a equatorial orbit and I point normal or anti-normal and go to warp, my craft keeps it's direction and just rotates around normal axis, returning to the same attitude every orbit, as expected.

However, when I tried the same thing with a polar (90deg) orbit I noticed my direction spiraling farther away from normal with each orbit. When I looked at the skybox with camera in locked mode it seemed as if my craft was rotating around celestial north-south axis.

So, does that mean that craft frame of reference is rotating with respect to the orbit/celestial sphere frame of reference?

Or am I missing something?

Edited by Silias

## Recommended Posts

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I'm not clear exactly what you're describing, but when close to the poles in some camera settings, the camera POV will rotate around the craft. The craft should not rotate with respect to the skybox, though.

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Unless something was changes, last I heard, a craft frame of reference was defined by some arbitrary units of the coordinate system. When you have time warp on, all rotary motions are stopped, so your craft always points the same way.

The reason for this is simple: When on an equatorial orbit, you're on a 0 degree plane relative to it's center of mass. However, in a polar orbit, moving above that 0 degree plane will change your aspect angle relative to the 0 degree plane, and the planetary center of mass.

The game handles time warping in the coordinate system by calculating each position of the polygons that are on your craft, and doesn't let them change angular degrees relative to the center of said coordinate system, which can be anywhere.

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if i am understanding correctly, heres an explanation.

If you are in a close to polar orbit and you use time warp, icons on the naval can seem to just change as you go around the planet. It isn't actually the craft changing direction, it is the fact the since you are in a polar orbit your position relative to the Body whose SoI your in changes. So say you're orbit kerbin passing under the south pole, it you point at the south pole then time warp to when you are above the north pole, your craft is still pointing the same direction but most of the points on the naval have changed.

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Imagine you are in a polar orbit of Kerbin, and the orbit is aligned with Kerbol. You go from directly between Kerbin and Kerbol to directly behind Kerbin from Kerbol in half an orbit.

Imagine also that you are pointing normally to your orbit. Thus you are pointing 90 degrees away from Kerbol at all points in your orbit.

In a quarter year, you should be still be pointing normal to your orbit, but since Kerbin rotated 90 degrees around Kerbol, you now point directly away from Kerbol.

A quarter year later, you'll be pointing 90 degrees away from Kerbol again, and after a total of 270 degrees, you'll face Kerbol for a while.

At all times, you should still be facing normal to your orbit, even though the navball swirls around the entire time.

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Thanks for the answers. After futher testing I thing it might be some bug, because it's not happeneing to every craft. One of the crafts I tested was only affected for half of the orbit!

Unfortunetaly I have too many mods, some of them messing with controls, to test this fully. One day I'll check it on a fresh install but for now I'll just leve it be:)

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No I get the same thing if I point a station towards the sun and come back 3 days later there is no telling which way the solar panels will be orientated. The Kerbal year is 425 days or something so the sun should have only rotated 1 degree.

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