Radial Attached Docking ports

[Pinchy]

OK - so I have got pretty good at docking now - have performed numerous missions to dock to create space stations/ Rescue missions etc etc - so I am not a noob.

However - when I have radial attached docking ports and I try to attach to another radial attached docking port - it just doesn't line up - apart from the fact that the RCS keys are all confusing which I can just about work with; when I have for example a Ship with say 2 docking ports on the side of the ship. Set to "control from here" so tip the ship sideways and guide it into my destination port "set as target". The vessel in question is a basic space plane with a Mk2 Cockpit and I have attached the docking port to the underside of the cockpit.

All aligned nicely - coming into Dock - Port aligned with the prograde marker perfectly... However when I am within about 40 Metres - it is absolutely obviously offline and seems to be trying to align with the centre of the space plane - and no where near the docking port. I keep letting it drift in and 0.4m/s and then boom smashes into side of spaceplane about 10 metres away from the docking port.

Eventually dock but having to manually perform the dock without aid from the navball as it is totally out?

Is this me - is the way I am using the docking port on the space plane - anyone else had this?

[Sharpy]

A nasty KSP bug causes the navball "target" to align with the root part and not the port. The direction matches the direction of the port but if the port isn't lined up with the root part, the actual point will be offset.

It combines orientation of the docking port and location of the root part. So you may seem perfectly aligned but instead of docking, you'll bump the target port with your root part.

Note this only applies to the "control from" port, not the target. So if you have the target's docking port aligned with its root part, you may try docking the target to your arrival instead of vice versa. If you can't, the only way is to eyeball it. While "prograde on target" still applies, the actual offset must be eyeballed.

Edited August 18, 2015 by Sharpy

[Brainlord Mesomorph]

Is it the root part? or the CoM?

I thought the navball gave you a straight line from the CoM through the docking port. Either way off-center ports are a problem. ignore the navball.

Protip: when docking, rotate your view and/or ship around so that horizon on the navball and the planet are the same. Then up/down and left/right are consistent on the navball, the screen and the keyboard. Docking is much more intuitive.

[Sharpy]

Nope, IIRC two ports back to back will present opposite directions, but the line won't pass through the ports, it will be just parallel to the line coming straight through the middle of the ports. I'm not 100% sure if it will be through the root part or through the CoM.

[Pinchy]

Sorry - but that is ....!! Surely it can't be difficult to fix this?

[Brainlord Mesomorph]

I posted a similar question once and was told it was the CoM

[Pinchy]

tosh!

[Sharpy]

Here we go, a testcase.

There are three ports on this vessel. One on the cockpit, one in the middle of the beam, and one on CoM, the big tank.

The rover was attached to the middle one and is straight ahead from it, but all the ports have the target some 20 degrees left from the current heading. This is where the target is in relation to the cockpit. So, the root part.

[Pinchy]

either COM or root part that is tosh!! If I set the Spaceplane to have it's root part as the docking port - would this fix it? so that I can guide the spaceplane into the "station ship" radial docking port?

[Brainlord Mesomorph]

Sorry - but that is ....!! Surely it can't be difficult to fix this?

yeah, we would imagine it should be a line perpendicular to the "Control from here" port.

but without the CoM as part of the equation, the ship would be very counter-intuitive in terms of steering. you could point at target, but trying to move toward it you would be unbalanced. This method is more accurate for approaching the target, but becomes inaccurate as you get close

[Pinchy]

Thanks again sharpy - the reliable tester to always reply to my posts

[Sharpy]

And here's the direction thing. I set the big tank as the root part. The port on the cockpit faces away from the rover. The line of sight in direction as pointed by the port goes straight from the tank at the rover though.

- - - Updated - - -

yeah, we would imagine it should be a line perpendicular to the "Control from here" port.

but without the CoM as part of the equation, the ship is very counter-intuitive in terms of steering. you can point at target, but trying to move toward it you are unbalanced.

FTFY.

Root part. Not CoM.

This time I made the docking port the root. It's almost perfectly aligned. Meanwhile the CoM is far off to the left.

[Pinchy]

Ok - so if I make the radial attached Docking port on the space plane as the root part - then I should be aligned to dock right?

[Sharpy]

Yes. Or have it in line with the root part, e.g. on the nose with a root part cockpit behind it.

[Pinchy]

hmm - that's interesting as I would expect the root part to already be the cockpit (to which the port is attached) - but maybe its not? I will check it later

[Brainlord Mesomorph]

Yep, root part not CoM.

CoM made (a little) sense. RootPart makes no sense at all.

SQUAD, pls fix this.

EDIT: most of my ships start with a big central fuel tank. So for me CoM is often root part.

Edited August 18, 2015 by Brainlord Mesomorph

[Sharpy]

hmm - that's interesting as I would expect the root part to already be the cockpit (to which the port is attached) - but maybe its not? I will check it later

Depends also on orientation of the port. If it's e.g. the MK2 shielded radial port, it's not likely to be pointing at the root part. Also, I'm not entirely sure *where* in the root part this points. E.g. MK3 cockpit is pretty big and you can definitely attach the port in a way that won't point at its "center".

[tater]

Hmm, so a Rockomax HubMax Multi-Point Connector might be a good part to make Root on a station until (if ever) fixed.

[Captain H@dock]

Sorry - but that is ....!! Surely it can't be difficult to fix this?

Obviously... However, this has been been extensively reported at least since I joined KSP (.90) and yet no action was taken on that matter. So maybe it isn't that easy, or maybe it isn't a priority...

I agree that it's crazy to leave something like that. especially when you have a linear docking part for spaceplane, which means almost everybody going mk2 spaceplane will run into the bug...

[Pinchy]

I still couldn't fix this - even setting the root part as the cockpit or the docking port - I was still so far off alignment it was a joke. I reverted my build to a Mk2 capsule instead with a front loaded docking port and problem solved - but yeah a total joke - thanks for all the input.

[monstah]

Get Navball docking alignment indicator. It's a shame that the usual answer is "there's a mod for that", alas, that's the case... As explained below, it unfortunately does not solve your problem. It's still a very good mod!

Plus, it's a VERY GOOD lightweight mod. Makes docking so easy it's almost boring.

Edited August 27, 2015 by monstah

[Pecan]

Get Navball docking alignment indicator

It is indeed excellent and the one I use because it's so minimal and unobtrusive but I don't think it corrects for target docking-ports that are not inline with the target's root.

On the other hand, Navyfish's docking mod - from which the navball indicator comes - has been updated to do so, IIRC.

As an alternative with better visuals, any of several mods which adds a docking-port camera is very cool. At any distance just use the navball indicator because it's "close enough", then align with precision using the docking cam.

[monstah]

but I don't think it corrects for target docking-ports that are not inline with the target's root.

Really? I've never had any problems with it, but then I'm no Whackjob and my designs are fairly simple.

- - - Updated - - -

Actually, come to think of it, you're absolutely right. I just shows port orientation, the position is still handled by the stock target marker.

My bad.

It's still a very good mod suggestion, tho.