For stations and ships to remember if RCS or SAS is left on and keeps them on.

[DMagic]

I still can't tell exactly what you want. But I think there might be some confusion what about SAS really does (even if it could be left on and active when the ship is out of range). SAS doesn't consider your orientation relative to the planet, it only tracks your orientation relative to the entire Kerbal universe. It will lock you one direction while everything else moves around you.

The easiest way to see this in game is to create a maneuver node and watch what happens as you follow it on the navball. Maneuver node directions are also oriented relative to the Kerbal universe. When SAS locks onto the blue maneuver node vector, your orientation will follow it in the short term. In the long term it will start to drift though, because the planet you are orbiting is also moving around the sun (the same thing happens with timewarp turned on; it doesn't happen when in orbit around the sun though).

Edit: Derp, now I'm getting myself confused. Maneuver nodes don't quite work this way. You will very slowly drift away from the blue maneuver node marker because your craft is oriented relative to the Kerbal universe, while the maneuver node is oriented with respect to the SOI it is in. That is why you slowly drift away as the planet/moon orbits around the sun.

So SAS will never be able to lock your position relative to the planet you're orbiting. The only exception, as has been noted many times, is when you are pointing directly north or south relative to the sun (thankfully all of the planets and moons are oriented the same way, regardless of inclination). The axis of your craft oriented along the north/south axis should stay that way while the rest of the ship rotates around it. This should remain true regardless of whether the ship is in range or not. The orbital parameters and orientation of the ship are stored in the persistence file, so this should be true. I haven't confirmed this for every possibility, but this should remain true even if you are in a non-equatorial orbit, or in the SOI of a planet in an inclined orbit (Moho, Minmus, etc... ).

Obviously you need to set the docking port that you want to use as the "control from here" point when orienting the craft in question. Anything else might result an incorrect orientation.

As for the complaint about not remembering SAS when you go out of physics range, I think you are right, and obviously RCS fuel will never be used. It gets turned off and you have to turn it back on. However, SAS behaves functionally equivalent to being in on-rails physics, both maintain your orientation with respect to the Kerbal universe. So the end result would be the same regardless of whether SAS was actually on when you went out of range.

Switching between the two crafts that you want to dock together could be a minor nuisance, but I don't really see what the problem is. When the station is loaded (which happens once you are closer than 2.4km away) switching should take no more than a few seconds. The parts are loaded once you reach this 2.4km range, not when you actually switch to a different craft. There is a delay of a few seconds while the physics activates, but this is not the same thing as actually loading the whole craft.

Once you set SAS on the station while both crafts are within physics range, and you remain in physics range, it should stay on and remain locked to its orientation (within the limits described above). If you bump into the station it should use any available RCS and torque to return to its original orientation. If you bump it so hard that you overload its ability to maintain its orientation then you need to be more careful.

As for what you describe above about the station no longer being oriented correctly once you return to it, I'm not sure. This shouldn't happen, the status of SAS makes no difference here; the orientation of the craft is stored in the persistence file and that orientation should remain constant as long as it is in on-rails mode. The only thing I can think of is that you aren't orienting the craft correctly (maybe you don't have the "control from here" set to the docking port you want to use), or that this is a bug.

The phantom rotation bug could easily cause this kind of thing. The craft may start out oriented correctly when you first approach it and it is loaded into the regular physics mode, but it could have started rotating by the time you get close enough to see it. I'm not completely sure what you're are describing, but it sounds like it could be this. When you say that the craft is rotating once you get close enough to try and dock do you mean that its orientation has changed, or that it is actively moving? By this I mean, if you switched to the craft would the navball be drifting without any input from you (beyond the normal amount of drift that occurs due to orbiting the planet), does activating time-warp stop this rotation?

If the craft is rotating without any input then you probably have some kind of phantom rotation. This can be caused by parts clipping together, but it can be really hard to track down the issue with bigger, more complex crafts.

Edited November 4, 2013 by DMagic
typos

[boomerdog2000]

Another issue that I don't think has been covered is pointing the station directly north will only help if you are in a perfectly equatorial orbit. If your orbit is only slightly inclined <1 degree directly north should be fine.

[Superfluous J]

Another issue that I don't think has been covered is pointing the station directly north will only help if you are in a perfectly equatorial orbit. If your orbit is only slightly inclined <1 degree directly north should be fine.

No it's been covered.

...Aim at your normal vector. For an equatorial orbit (which most orbits are) that means you want to aim your docking port North or South...

...You want to aim at the NORMAL vectors, which are (for most orbits) North and South...

...The only orientation that always stays the same (if you are on equatorial orbit) is North/South....

...if you're talking about your station not staying aligned to the normal vectors (north/south usually) then yes, the game already does that...

And it's even been questioned once and I don't know the answer to the question but am intrigued by it:

...The axis of you craft oriented along the north/south axis should stay that way while the rest of the ship rotates around it. This should remain true regardless of whether the ship is in range or not. The orbital parameters and orientation of the ship are stored in the persistence file, so this should be true. I haven't confirmed this for every possibility, but this should remain true even if you are in a non-equatorial orbit, or in the SOI of a planet in an inclined orbit (Moho, Minmus, etc... )...

[DMagic]

And it's even been questioned once and I don't know the answer to the question but am intrigued by it:

Now I'm not so sure about that, trying to conceptualize this stuff in my head can make me a little dizzy. I need to try this out in-game and see what happens.

[boomerdog2000]

No it's been covered.

And it's even been questioned once and I don't know the answer to the question but am intrigued by it:

I guess I wasn't clear enough. I don't believe he has said whether or not he is in a perfectly equatorial orbit, and therefore whether or not pointing north or south would help.

[Superfluous J]

Now I'm not so sure about that, trying to conceptualize this stuff in my head can make me a little dizzy. I need to try this out in-game and see what happens.

I've got a ship in a polar orbit around Minmus right now and the north (and south) poles are spinning around it like a top, once each orbit. There is actually no point on the navball itself that stays still, but I have Enhanced Navball installed and the normal vectors (purple triangles) are stationary with respect to the background stars.

[Damaske]

For the station spinning that i experience was the following station minus the arms, The orange tanks, and was just the center piece.

I use Mechjeb, it was at 0 inclination, With Smart ASS in orbit with -MNL on left it in orbit dropped down to KSP made the first arm and came but up with no trouble as with the 2nd one after three rebuilds. Then as i was trying to connect the third on that was when the station was as i put it wobbling.

There also was a lot of debris in near orbit as with one that was moving fast away.

[boomerdog2000]

Well in this case SAS may actually be your problem. Without any struts, when the station turns, those fuel tanks are going to fight it and sort of bounce. I've had some of my earlier stations go into a sort of resonance and bounce out of control. Are there control modules with torque on those outer fuel arms? If there are try turning them off.

[Damaske]

I don't think there is any, but when i rebuild the arms I'll not add any torque wheels. But i had planed to build around and connect the arms into a large square. I did an experiment with multiply docking ports and they all connected once next to each other. The next phase of testing was not yet done due to falling asleep on the keyboard. That would have been docking both sides of something to fill a gap between another two.

[Tuareg]

how many ignorant ppl... isnt even worth answering

[boomerdog2000]

I don't think there is any, but when i rebuild the arms I'll not add any torque wheels. But i had planed to build around and connect the arms into a large square. I did an experiment with multiply docking ports and they all connected once next to each other. The next phase of testing was not yet done due to falling asleep on the keyboard. That would have been docking both sides of something to fill a gap between another two.

No I wasn't saying don't add SAS to the fuel tanks. You're going to need that if you want those things to be maneuverable enough to dock. Just try turning off the SAS in the fuel tanks, once they're docked. Sometimes the SAS in station modules can fight itself, at least it did in .21. Even then if the station has to do any serious turning you're still likely to run into trouble. I recommend gratuitous use of the kerbal's angular velocity canceller (timewarp).

[Damaske]

how many ignorant ppl... isnt even worth answering

Your comment just proves how ignorant you are also, The only stupid question OR idea is one not asked or looked into. go back to your bridge troll!

No I wasn't saying don't add SAS to the fuel tanks. You're going to need that if you want those things to be maneuverable enough to dock. Just try turning off the SAS in the fuel tanks, once they're docked. Sometimes the SAS in station modules can

fight itself, at least it did in .21. Even then if the station has to do any serious turning you're still likely to run into trouble. I recommend gratuitous use of the kerbal's angular velocity canceller (timewarp).

I can have the SAS on the tug ship to help dock it. I also balance out the tanks them self with the RSC balance mod and then attach the tug-ship via docking or coupler.

I recommend gratuitous use of the kerbal's angular velocity canceller (timewarp).

First thought was "This is Kerbal Space Program NOT Gratuitous Space Battles" lol, but wait if somehow you can combine both .....

[DMagic]

I've got a ship in a polar orbit around Minmus right now and the north (and south) poles are spinning around it like a top, once each orbit. There is actually no point on the navball itself that stays still, but I have Enhanced Navball installed and the normal vectors (purple triangles) are stationary with respect to the background stars.

Ok, now I've got it, and it makes sense, too (at least to me). A ship in an equatorial orbit around any planet/moon that is pointed directly north or south (that would be along the N or 180^o line, directly between the orange and blue hemispheres of the navball) will stay that way forever. Every planet has their north/south axes aligned along the same plane regardless of their orbital inclination.

As for non-equatorial orbits, you are right, you won't stay pointed directly at that point on the navball. However, if you point at the center of the N/180^owhen you cross the planet's equator your orientation will oscillate along the N/180^o line. The amount of oscillation depends on your inclination. So in a 45^o orbit you will move along the N/180^o line about half-way up and down the blue and orange hemispheres.

So you are technically still pointed directly north/south (with regard to the Kerbal universe) during the entire orbit. The navball moves because your orientation with respect to the planet changes, but your real orientation doesn't change.

Therefore this method of fixing the orientation of your docking ports should work regardless of what your inclination is. The navball will move, but your two crafts (one pointed directly north, the other pointed directly south) will remain facing each other even if it takes an entire orbit to dock.

So don't listen when someone tells you that you have to be in an equatorial orbit to keep your docking ports aligned. Of course, I could be horribly wrong and maybe you should listen... or just try it out. The part about aligning your craft when you cross the equator is important though. If you try to do it at some other point it will be difficult to line up correctly and your craft probably won't stay oriented.

[boomerdog2000]

Yep, the only difficulty is that without a normal indicator on the nav-ball, your only option is to eyeball it if you're not in an equatorial, so equatorial is generally the easiest.

[kurja]

Yep, the only difficulty is that without a normal indicator on the nav-ball, your only option is to eyeball it if you're not in an equatorial, so equatorial is generally the easiest.

set up a maneuver node for normal/antinormal dv, align to the blue marker and you're all set regardless of your inclination?

[Superfluous J]

set up a maneuver node for normal/antinormal dv, align to the blue marker and you're all set regardless of your inclination?

Yup, that works fine in a pinch (ie, when you don't have EnhancedNavBall installed)

[boomerdog2000]

set up a maneuver node for normal/antinormal dv, align to the blue marker and you're all set regardless of your inclination?

I can't believe I haven't thought of that before...

[DMagic]

set up a maneuver node for normal/antinormal dv, align to the blue marker and you're all set regardless of your inclination?

Are you sure this works in a non-equatorial orbit? The maneuver node vectors are aligned relative to your orbit, so the purple, normal/antinormal, vectors are always 90^o away from the prograde/retrograde vectors. This means that in an inclined orbit they would point either up or down from the plane of your orbit (which is of course different from the equatorial plane) and therefore not directly north/south.

Maybe I'm missing something; I'll have to try this out.

[Kasuha]

Are you sure this works in a non-equatorial orbit? The maneuver node vectors are aligned relative to your orbit, so the purple, normal/antinormal, vectors are always 90^o away from the prograde/retrograde vectors. This means that in an inclined orbit they would point either up or down from the plane of your orbit (which is of course different from the equatorial plane) and therefore not directly north/south.

Maybe I'm missing something; I'll have to try this out.

If this is about aligning docking ports then yes, you need to orient it along normal of your orbit. North/south only works for equatorial orbits.

[DMagic]

If this is about aligning docking ports then yes, you need to orient it along normal of your orbit. North/south only works for equatorial orbits.

I see it now. Aligning along the normal/antinormal vector lets you point in the same direction relative to the planet during the entire orbit; only your rotational axis will change.