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paul23

How to make docking less an exercise in frustration?

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Today I tried to dock a semi heavy lifter to a very heavy station. I spent over an hour trying to align and dock those objects; an utter test of patience and frustration.

 

Now with two light objects it's a breeze and easy: you can rotate both to face each other and then just move close. However considering a "very heavy" object that you cannot feasibly rotate. Now  the other object needs to be aligned well enough. Often when I think they are aligned and I start moving forward I just notice that I didn't align in the "depth" part. And I just miss by 1-2 meters. Then I try to align in that direction, but inadvertently (since we only have two direction control and not a full 360 degrees freedom) I miss in another direction.

 

The other option "moving towards target" often means you hit the target under angles that lead to huge jumps when it fails to attach. (like shooting away with several meters per second).

 

If only I could see how I align with the *target* port. See where I am on the plane parallel to the target port (x,y - positive Z axes would be facing out of hte port).

 

 

How do you line up larger crafts that take several seconds to rotate?

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On 11/8/2019 at 12:33 PM, Kerbart said:

The secret to easy docking is scribbled on the walls of the bathrooms in Carnegie Hall. If you don’t know how to get to Carnegie Hall, just ask.

I have been to Carnegie Hall, and I found the sacred texts, they are thus:

Both threads have lots of good resources, ideas, suggestions, and links, some of which have already been parroted here. 

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Are you willing to use a mod?

Docking heavy craft in stock is, once again, a matter of practice. There are a couple things you can do to make it a little easier -- put enough balanced RCS on your craft to give you nicely independent translation/rotation modes, and swinging the camera all over the place to get a really good idea of alignment while maintaining a nearly perfect mental idea of which rotation/translation directions correspond to which buttons even while looking at the craft from odd angles. But it's always kinda hard and annoying and takes a while.

 

 

Edited by bewing

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Set the target ships port as the target and control from your docking port. 

Rotate the camera so that rcs pushes you in sensible directions compared to your view.

Fly on the navball not just visually.  Locking  SAS to target will keep the target indicator centred on the ball,  but i prefer to get it all pointing in roughly the right direction first if it's a heavy craft and slow to rotate.  Then nudge the prograde vector on to the target marker, but be prepared to move it a bit vertically/sideways to get yourself square on to the port. 

It's a challenge to begin with but it gets easier with practice.   For new aligning the camera properly made a huge difference. 

Edited by RizzoTheRat

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49 minutes ago, RizzoTheRat said:

Rotate the camera so that rcs pushes you in sensible directions compared to your view.

Even better, hit v a few times to go into locked mode, then do this. It will guarantee your ship and navball agree on directions.

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Good point, that's the step I missed out and that's the bit that really made a difference for me.

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No mention of mods yet?

Docking Port Alignment Indicator - Navyfish's classic
Navball Docking Alignment Indicator - the minimalist variant I prefer
Mechjeb - display the metrics you're asking about, all the way to the docking autopilot if you want it to (uses a lot of monoprop).

Launch is a thunderous demonstration of raw power but docking is the silent, graceful, ballet of space perfection.
It takes most of us a lot of practice to really 'get it' but when you do docking can be very satisfying, almost therapeutic.

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7 hours ago, RizzoTheRat said:

Fly on the navball not just visually.  Locking  SAS to target will keep the target indicator centred on the ball,  but i prefer to get it all pointing in roughly the right direction first if it's a heavy craft and slow to rotate.  Then nudge the prograde vector on to the target marker, but be prepared to move it a bit vertically/sideways to get yourself square on to the port. 

Learn your navball, love your navball!

If you switch to the other craft (let's call that "station" - which doesn't move or rotate - as opposed to "ship" - which can move and rotate), select the target and "control from" the docking port, then that will show you if the ship is aligned correctly with the docking port. If the target marker is in the center of the navball of the station, then the ship is well aligned with the docking port of the station. The next item is that on the navball the target marker will move radially away from the target-mode prograde marker. So if you move the ship so that the the center of the navball, the target marker, and the prograde marker all align on the navball of the station, then you are on the way to get them aligned. As usual this takes lots of fine (and not so fine) tuning, so my method requires a lot of switching between station and ship.

A further complication is that the prograde marker will point in the direction of the center of mass of the crafts, so if you want to dock to a docking port that is not aligned with the center of mass then you need to take that into account when you get close.

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9 hours ago, paul23 said:

How do you line up larger crafts that take several seconds to rotate?

The first part is:

7 minutes ago, AHHans said:

Learn your navball, love your navball!

After that, when you select 'Control From Here' on the docking port you want to use, you may find some assistance when you make certain that you also click 'Aim Camera' (it may be an advanced tweakable; you can activate advanced tweakables in the settings) so that the locked camera that @5thHorseman mentioned centres on the docking port instead of the centre of mass of the vessel.

Also, large vessels that take several seconds to rotate have more angular momentum; they also take several seconds to stop rotating.  Consider using fine control (toggled with the caps lock key; when active, the pointers for roll, pitch, and yaw in the lower left corner turn blue rather than orange) for small adjustments and better balance when you align with RCS.

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I wish to *not eyeball it*.. I hate having to do 3d stuff in a 2d screen. I really wish to have a numerical approach so I can actually *see* the angles and correct them. Instead of having to fly by heart.

Edited by paul23

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58 minutes ago, AHHans said:

A further complication is that the prograde marker will point in the direction of the center of mass of the crafts, so if you want to dock to a docking port that is not aligned with the center of mass then you need to take that into account when you get close.

Once you're within a couple of km (I think) of the target ship, right click on the docking port on the target ship and you can select that docking port as the target rather than the ships centre of mass.  Similarly with "control from here" on the docking port on your own ship.

 

27 minutes ago, paul23 said:

I wish to *not eyeball it*.. I hate having to do 3d stuff in a 2d screen. I really wish to have a numerical approach so I can actually *see* the angles and correct them. Instead of having to fly by heart.

That's why you want to use the navball to show the directions you're facing and moving in relation to the target, so you're only eyeballing the up/down and left/right offset in 2 dimensions.  I believe some of the docking aid mods mentioned will give you that kind of info numerically.  Or you could have a play with Kerbal Operating System and calculate and display the numbers yourself...and then take it a step further and write your own code to dock 2 ships.  Getting that working was one of the most satisfying things I've done in KSP so far.

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Big thumbs up from me for Navyfish's docking port alignment mod.  Get your approaching vessel all correctly oriented and then simply translate in to position.  Simple.

 

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1 hour ago, paul23 said:

I wish to *not eyeball it*.. I hate having to do 3d stuff in a 2d screen. I really wish to have a numerical approach so I can actually *see* the angles and correct them. Instead of having to fly by heart.

You definitely should try Docking Port Alignment Indicator, then.  The navball indicator is strictly visual and doesn't give the numeric information that you want.  Keep in mind that a new KSP version was released recently, so it may not be updated yet.

Also, even DPAI doesn't give you everything numerically; it'll give closing distance, which is the z-axis separation you asked for.  It gives roll angle numerically, as well.  X-Y alignment is still visual.

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Well it's that the x-y alignment (translation) isn't possible using the navball.. Exactly that is what I have trouble with. If I follow the navball the porst will 'kiss' each other: however they'll be under an unwanted angle.

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The secret to easy docking is scribbled on the walls of the bathrooms in Carnegie Hall. If you don’t know how to get to Carnegie Hall, just ask.

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4 hours ago, paul23 said:

Well it's that the x-y alignment (translation) isn't possible using the navball.. Exactly that is what I have trouble with. If I follow the navball the porst will 'kiss' each other: however they'll be under an unwanted angle.

If you aim your target ship's port normal and your docking ship's port anti-normal then they'll be lined up and not wander.

Other than that your only option is one of the (at least)  3 mods that help align ports.

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Docking can be one of the biggest learning curves in KSP. Here's how I first learned to dock massive ships.

  1. Set your heaviest, slowest ship (the station) to align the port with the "normal" direction. Right-click the port to "control from here" and then let SAS slowly do its job. If you're in the usual eastward launch counterclockwise orbit around Kerbin, that docking port will be aiming north, and tends to stay north even if the rest of the ship rotates during orbit.
  2. Next step is to rendezvous your heavy lifter with the station. Get close to the station, then slowly maneuver to be slightly "above" (north in my Kerbin example) of the station's docking port. Right-click to control from the heavy lifter's docking port, set SAS to "target", and let your lifter slowly rotate to align the docking ports.
  3. Gently use RCS to move the lifter towards the station. Watch the navball and keep the yellow direction indicator centered. Regular docking ports like a speed around 0.3 m/s or slower, the klaw needs 1.2 m/s.

Note that if you switch control back and forth between ships, SAS mode may turn off or reset to heading hold. In my copy (heavily modded 1.7.3), SAS continues to work in the correct mode for the ship I was controlling, but resets for the ship I just took control of. Keep the station targeted on "normal" and the heavy lifter on "target".

All this assumes your docking ports are aligned along the centerline of the ship. If you have a radial port on the side of the ship, SAS aims at the center of mass rather than the ports, and you may need to manually point one or both of your ships to keep the target indicator and direction indicator centered.

I find 2 mods useful for docking. Better Time Warp (or similar) allows tweaking physics timewarp (Alt->). I set the maximum speed to 10x (default is 4x) so I waste less time watching massive ships align themselves. Just make sure to go back to 1x before actually docking.

The other docking mod is helpful for all docking, and essential for radial ports IMO. It gives a camera and a green indicator as things get close to docking.

 

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7 hours ago, Kerbart said:

The secret to easy docking is scribbled on the walls of the bathrooms in Carnegie Hall.

That's just too important not to follow-up :-)

Say, Kerbart, how do you get to Carnegie Hall?

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25 minutes ago, Pecan said:

That's just too important not to follow-up :-)

Say, Kerbart, how do you get to Carnegie Hall?

Why, practice, practice, practice!

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22 hours ago, RizzoTheRat said:

Once you're within a couple of km (I think) of the target ship, right click on the docking port on the target ship and you can select that docking port as the target rather than the ships centre of mass.  Similarly with "control from here" on the docking port on your own ship.

That will only make the target indicator on the  navball be the way you expect to be. But if the center-axis of the docking port on the currently controlled vessel is not going through the COM then a target that is moving directly to that docking port is not moving directly to the COM. Thus the target-prograde marker will not be in the center of the navball. You can test that by having several docking ports along the length of a station/ship, all parallel and oriented the same way. If you then switch "control from here" between these ports with a target in close proximity then you'll see that the target direction marker moves around as you would expect, but that the target-prograde marker does not.

20 hours ago, paul23 said:

Well it's that the x-y alignment (translation) isn't possible using the navball.. Exactly that is what I have trouble with. If I follow the navball the ports will 'kiss' each other: however they'll be under an unwanted angle.

That's what I'm saying: if you switch to the other vessel (and set it up correctly) then you'll see if you are coming from the right angle or not, and in which direction you need to fly to correct that angle.
[Edit:] Or you use one of the mods that were already suggested.

Edited by AHHans

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On 11/8/2019 at 5:44 AM, paul23 said:

How do you line up larger crafts that take several seconds to rotate?

The stock solution is to have both aligned in the "normal"  or "anti-normal" direction. That way, the ports will at least be parallel to each other. That, and locking the view "so that rcs pushes you in sensible directions compared to your view" (suggested above) will help a lot.

Also, for the final few meters, don't even look at the vessels. Steer by navball.

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7 hours ago, Laie said:

The stock solution is to have both aligned in the "normal"  or "anti-normal" direction. That way, the ports will at least be parallel to each other. That, and locking the view "so that rcs pushes you in sensible directions compared to your view" (suggested above) will help a lot.

Also, for the final few meters, don't even look at the vessels. Steer by navball.

yeah but then it still feels like fitting a thread through a needle: you try, fail, try again, fail again without really making progress.

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8 hours ago, paul23 said:

yeah but then it still feels like fitting a thread through a needle:

What you are trying to do is very much like threading a needle, and once you've made sure that the ports will be about parallel to each other, I don't think it gets any easier than that.

But, steering by Navball for the final few meters isn't that hard:  just make sure that your prograde and target markers line up (picture stolen from the illustrated docking guide):

Ij8Wl0w.png

There's a bit of experience involved... given a few tries, you'll figure out what kind of error has which results, and soon you will use that knowledge to your benefit.

Oh, and have we already mentioned that there is such a thing as "fine controls" (CapsLock by default)? This makes it much easier to carefully nudge your vessel.

--

Finally, one gotcha: when determining the direction to target, the game is looking at the docking port you're targeting, but it's looking from the center of mass of your vessel. When your docking port is attached somewhere at the side of the vessel, this can lead to serious parallax errors. In that case, by all means, resort to autopilots.

Edited by Laie

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6 hours ago, Laie said:

What you are trying to do is very much like threading a needle, and once you've made sure that the ports will be about parallel to each other, I don't think it gets any easier than that.

But, steering by Navball for the final few meters isn't that hard:  just make sure that your prograde and target markers line up (picture stolen from the illustrated docking guide):

Ij8Wl0w.png

There's a bit of experience involved... given a few tries, you'll figure out what kind of error has which results, and soon you will use that knowledge to your benefit.

Oh, and have we already mentioned that there is such a thing as "fine controls" (CapsLock by default)? This makes it much easier to carefully nudge your vessel.

--

Finally, one gotcha: when determining the direction to target, the game is looking at the docking port you're targeting, but it's looking from the center of mass of your vessel. When your docking port is attached somewhere at the side of the vessel, this can lead to serious parallax errors. In that case, by all means, resort to autopilots.

I tried to line up, but even then I 'miss': my ship hits, but the docking ports (located at the sides) are off by half a tank.

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1 minute ago, paul23 said:

I tried to line up, but even then I 'miss': my ship hits, but the docking ports (located at the sides) are off by half a tank.

Blast.

As mentioned in my previous post, that's a problem with the game giving you wrong directions. Small wonder that you're frustrated.

The only stock workaround I can think of would be to "aim camera" at the docking port you're using, then rotate view and zoom in, so far that you're effectively looking out of the port. And then fly visually. Good luck.

Other than that, try mods.

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9 hours ago, Laie said:

Blast.

As mentioned in my previous post, that's a problem with the game giving you wrong directions. Small wonder that you're frustrated.

The only stock workaround I can think of would be to "aim camera" at the docking port you're using, then rotate view and zoom in, so far that you're effectively looking out of the port. And then fly visually. Good luck.

Other than that, try mods.

Click docking port on your ship and turn on control from here, then your directions will be correct, set docking port of other vehicle as target, align prograde/retrograde marker with target marker and then use SAS to align docking port axis with movement vector (align V marker with O and X markers). Turn SAS off just before contact.

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