Docking Port Normal Indicator on Gimbal?

[neilmct]

Hi.

Newb here. I have been having a hell of a time with docking. Followed a few of the tutorials on youtube etc and rendevous/closing to the target is fine, but the docking.. gah! I've had less frustrating times on QWOP.

Perhaps I am doing something wrong.. or perhaps I'm just trying to dock something that is too long and wobbly, maybe with poor RCS placement.. but generally what happens is:

1. move to the appropriate side of the station.

2. zero velocities (or as close as I can)

3. select the docking ports on both ships

4. choose chase cam and rotationally line up with the station - one east the other west.

5. use RCS to line up with the purple target indicator (up/down left/right translation)

6. then use RCS to close the distance

Problem is by the time I get to the target I am inevitably approaching from some funny angle.

I think my problem is that either:

If I keep my ship heading east during 5 and 6 then by the time I finish my up/down-left-right orientation the station is no longer pointing west as it is orbiting the planet. (Yes I do have SRS turned on for the station.. that's right isn't it?)

Alternatively if during 6 I ignore the easterly orientation and instead keep myself rotated toward the purple target indicator then again I'm still hitting it at a funny angle by the time I approach. I think in this case it is because my up/down-left/right velocities are not absolutely perfectly zeroed so as I close keeping the thing lined up with the purple marker makes me turn.

So basically my question is: am I doing something obviously wrong?

Also is there some add-on that will show the relative x-y-z components of my velocity to a target with some fine grained detail? The velocity+yellow gimbal indicator seems very hard to use at low velocities with translations.

Also is there some add-on that shows the normal to the target docking port on the gimbal? This just seems like such a no-brainer that I feel I must have missed something with this whole docking thing. Basically so docking would be:

3. zero volcities

4. Line up with the (say red) normal to docking port indicator so you are aligned rotationally.

5. Keep yourself rotationally aligned with the red marker and move up/down-left/right until the purple target indicator overlaps the red one. Then you are lined up both in terms of rotation and x/y translation.

6. zero your x-y velocities

7. increase your z velocity - dock

I would have thought it should be that simple. Please excuse me if my newbiness is ignoring something obvious.

[falofonos]

http://kerbalspaceprogram.com/lazor-docking-cam/ includes x , y, z data as well as the handy camera view.

It's not totally impossible to dock with a rotating target, just practically impossible.

I'd recommend aligning the target spacecraft / station north -> south, that way the orbit should not be a problem. Clicking the speed indicator on the top of the virtual horizon ball display until it says "target" will give you a nice relative speed number and give you some vector relative to target feedback.

[Zephram Kerman]

You can right-click on the docking port, and select 'control from here' which reorients the nav ball relative to that part. So now the target and direction of travel are in the middle where you can actually see them. If you are moving toward the target at 1 m/s or so, the prograde marker should be stable enough.

Falofonos' tip about aligning to north/south might seem like a small thing, but it really makes the approach much easier by eliminating rotational drift.

One more thing. It's ok to adjust while approaching the docking port. Looking at the nav ball markers, use lateral RCS to put the prograde marker on the opposite side of the target marker.

[Scottiths]

As Falofonos said, try aligning your space station perpendicular to the direction of its orbit. IE: if you are on a polar orbit you want to align along the 90 or 270 degree line. If you are in a equatorial orbit you want to align on 0 (north) or 180. The horizon rolls around these points depending on the inclination of your orbit and by aligning this way you can keep everything set up. If you use MechJeb there is a Par+ and - that will automatically make you parallel.

Another problem might be that your RCS is not balanced. If you try to translate with unbalanced RCS then you will introduce rotation to your spacecraft. Apparently this used to not happen because RCS would thrust harder the closer to CoG it was. They removed that feature due to some insurmountable problem (or took the easy fix, not sure which). Hopefully they put something like that back in.

[RoboRay]

As noted above, turn both craft so the docking ports are aimed north and south. Approaching along the Normal axis gives you a stationary docking target.

[CalculusWarrior]

When making preparations for docking, I generally switch into 5x time warp for a second, which freezes both ships in place. Aligning both ships about a common axis is a good idea, but be careful: you are both hurtling above the planet's surface at >2 km/s, and so after a few minutes, the east on your navball will no longer point towards the same direction as it did when you lined it up. Either attempt to dock as quickly as humanly possible, or switch on ASAS as soon as you get your ships lined up, and don't switch that orientation until you've docked.

[neilmct]

These are some very nice tips. Thank you all very much