Illustrated guide to docking

[Snark]

After just getting something into orbit (and perhaps a Mun landing), the next big challenge for a new KSP player is how to dock in orbit. Here's a step-by-step illustrated guide for how to do so.

(There are various techniques... and plenty of other guides out there. This is just how I like to do it. I hope you may find it useful.)

(Author's note:  Please forgive the out-of-date screenshots.  This post is ported from a blog entry I made on an older version of the forum software, back in 2015, so screenshots reflect what KSP looked like at the time.  The appearance has changed a bit since then, but everything I wrote here still applies.)

 

The big picture

Docking proceeds in four main steps:

1. Rendezvous.
   • This is the part where you use maneuver nodes to arrange for your ship and the target to be in the same place at the same time, or at least as close as possible.
   • Careful fiddling with the maneuver node will generally get you a rendezvous within a kilometer or so.
2. Fine tuning the rendezvous.
   • This involves making small burns as you approach the target, in the last few kilometers, so that your closest approach is zeroed in to a few dozen meters (from the kilometer-or-so you got in step 1).
   • This involves close observation of the navball and light touches on the throttle.
3. Kill relative velocity to target, right when you're at your closest approach.
   • Also a navball-and-throttle operation. You're now parked right next to the target, just a few meters away.
4. Actually dock.
   • This involves eyeballing docking port alignments in the camera view (unless you have a mod installed to show docking alignment on the navball, which is a big convenience).
   • This is where you use your RCS thrusters to jockey for position.

The following sections go into detail on these steps.

 

Step 1: Rendezvous

Navigation tool: Maneuver nodes and map view
Control via: Main engine and throttle

The first thing you have to do is to send your ship on a course that will put it and the target in the same place at the same time-- or, at least as close as you can get with maneuver nodes.

I'm assuming here that you in fact have maneuver nodes (i.e. you've unlocked them by upgrading the tracking station), and also that you're familiar with how to use them.

I'm also assuming that you know how to set up a fairly good orbital rendezvous with maneuver nodes, i.e. one that will get you a closest approach within a kilometer or two. This is a big assumption: doing that is actually a significant challenge, and if you're a new player just learning how to dock, there's a pretty good chance you may not have mastered "orbital rendezvous with maneuver nodes" as a skill yet.

However, I'm not going into it here, for a couple of reasons:

• It's a whole complex topic in its own right, and this blog post is about docking rather than general orbital navigation. (I may add a "how to rendezvous" post at some time in the future, in which case I'll link to it from here. If my glossing over this part is frustrating, please let me know so that I can gauge demand. )  Here's a handy guide to rendezvous (not mine).
• The details of how to set up a rendezvous vary a lot depending on the starting situation (e.g. launch from surface to direct intercept, or two craft already in orbit, are their orbits coplanar or not, etc.).

But even though I'm not telling you how to do it here, I can show you what "good" looks like:



Exactly what your own situation will look like depends heavily on circumstances. But the important bit is that it's a close rendezvous. You want the closest approach to be as close as you can manage with the maneuver node-- no more than 2 km at most, preferably under 1 km. (In the above example, it's 0.3 km, which is pretty good.)

One more side note:

• See how the target (yellow) line and my own ship's (cyan) line are crossing each other like an X, rather than being close to parallel to each other at the point of intersect?
• That's actually pretty bad: it means that they're orbiting in significantly different directions at the point of intersect, which in turn means that they're going to have big relative velocity to each other, which means I need to burn a lot of fuel.
• I've done it that way deliberately, here, so that this guide can show you "how to dock" even if the situation's not perfect. Ideally, you will set it up better than this, so that their relative velocity at closest approach will be smaller, and therefore your job will be easier in the remaining steps.

 

Step 2: Fine-tune the rendezvous

Navigation tool: Navball and map view
Control via: Main engine and throttle

Your eventual goal (in step 3, below) is to coast to a stop so that you're parked right next to the target (as in, just a couple of dozen meters apart).

Chances are, however, that unless you're either super lucky or an ace at maneuver-nodes, the rendezvous that you set up in Step 1 above will only get you to within a few hundred meters at best-- perhaps a kilometer or two. You'd like to be closer than that when you match velocities, since your final approach (using RCS) will be very slow, just centimeters per second, and you don't want to have to do that for a kilometer or more.

So the way to solve that is to make minor course adjustments with light touches on the throttle of your main engine, using the navball for guidance. Here's how:

First things first: Make sure navball is in "target relative" mode

Once you get close to the target, you don't care what your orbital velocity is. You only care about your velocity relative to the target. Chances are, the navball is probably in "Orbit" mode when you're in orbit (the game does that automatically, unless you've manually tinkered with it).

Normally, when you approach your target within 60 km, the navball will switch automatically to "Target" mode instead of "Orbit": this causes your prograde/retrograde markers to indicate your target-relative velocity rather than your orbital velocity, which is what you want. It looks like this (note the "Orbit" or "Target" indicator at the top of the navball):



...Typically, it will do this automatically for you and no action is required on your part. I only bring it up because it's possible this might not happen, and you need to make sure that the navball is in "Target" mode, or nothing after this point will make any sense. You can change the mode manually by clicking on the label. This will toggle the navball between Orbit, Surface, and Target modes.

Why this fine-tuning step is needed

As you get within several kilometers of your target, your navball will start to look something like this (again, make sure your navball is in target mode):


This looks pretty good: your marker (target relative velocity) is pretty close to your marker (target direction). The fact that these two are close together means that you are heading almost directly towards your target.

However, the key word here is "almost". If you just coast towards your target and do nothing, you'll see the marker slide farther and farther away from the marker, like this:


That's because you're not heading directly at the target. Unless you got super lucky (or are an ace) with the original maneuver node, your closest approach is likely to be at least several hundred meters away from the target. This means that without any course corrections, you're going to go past it, and the target will slide off the side of your navball in the same way that someone standing beside the road slides off to the side of your windshield as you drive past them.

Therefore, you need to adjust your course when you get close by, so that you are sitting right next to your target (and not a kilometer away) when you come to a stop relative to it.

What to do

When you get reasonably close to your rendezvous (say, when it's 1 minute away, which you can see in the map view when you mouse over the intercept marker), start the process.

What you're trying to do is to move your marker so that it's precisely centered on your marker (i.e. so that you're heading directly at the target). To do this, start by lining up your navball so that your crosshairs, , and are exactly lined up in a straight line, like this:


Note that the marker is exactly on a straight line in between the navball crosshairs and the marker.

Why do we do this? Well, firing your engines "pushes" the marker away from the center crosshairs on the navball. Since what we want to do is move the marker onto the marker, then by lining the navball up this way, it will "push" the marker in the direction we want it to go.

Once you've got it lined up, gently throttle up to move the marker. How much throttle you need will depend on your ship's TWR and how big your target-relative velocity is. So just keep a careful eye on the navball, gently throttle up, and be ready to kill the throttle immediately when things line up.

As your engine burns, you will see the marker drift towards the marker, like this:


When the two markers line up perfectly, cut throttle. (Don't worry if it's not pixel-perfect; all that matters is that it's better than it was. If you're off by a smidgeon, what will happen is that as you get closer to the target, the two markers will drift apart again, and you can do this correction maneuver again. Repeat as needed.)


Prograde fine-tuning (if you end up too slow while still far away)

In the preceding discussion, we did all our fine-tuning while thrusting close to . I recommend this because it kills two birds with one stone, thus saving dV: not only does it fix our heading to get a close approach to the target, but it also helps kill some of our velocity (since we'll need to reduce that down to zero in the next step).

However, it could happen that you end up approaching too slowly while still far away: i.e. your target-relative velocity is very low while you're still at a long distance. In such a case, fine-tuning in the prograde direction is an option.  Details in spoiler.

Spoiler

Maybe you got overzealous in the next step and killed your velocity while you're still far away from the target. Or maybe your maneuver-node rendezvous has you at a very slow closing speed with the target. Or maybe you're just impatient. In other words, you could have a situation like this:


In a situation like this, you can do fine-tuning in the prograde direction instead of retrograde, so that you accelerate towards the target. The important thing to remember is that thrusting "pushes" the marker away from the navball crosshairs, but it "pulls" the marker towards the navball crosshairs.

Therefore, to do a maneuver like this, you flip around so you're pointing close to . You line things up so that the marker is on a straight line in between the navball crosshairs and the marker, like this:


Then you gently thrust, which will "pull" the marker towards the navball crosshairs (and therefore towards the marker). Cut the engine when they get lined up perfectly, like this:


Now you're headed straight at the target. You can proceed to Step 3 now. (Or, if you think you're still going too slow towards the target, you can line up on your crosshairs and thrust some more.)

I recommend using this prograde technique sparingly: it wastes dV, since you're using fuel to increase your target-relative velocity, which you'll then need to spend even more fuel later to cancel out when you get close to the target.

 

Step 3: Kill relative velocity to target

Navigation tool: Navball and camera view
Control via: Main engine and throttle

This is the easiest part of the process, since there's little steering involved. All you have to do is slow down to a stop in the right place.

As you approach the target, line up your navball so that you're pointing perfectly retrograde (i.e. the marker is centered perfectly in the crosshairs-- again, make sure your navball is in target-relative mode, not "orbit"). If you have a level-1-or-better pilot, or if you have a HECS-or-better probe core, then this is easy: just choose the "hold retrograde" SAS button (red arrow in the illustration below). But if you don't have that convenience, just do it manually.


As you approach the target, the marker will want to drift away from center; if necessary, you can do more correction as described above in step 2.

Reduce your speed gradually as you approach the target. If you wait too long, you'll overshoot; if you start too soon, you'll go too slowly and it takes forever to close the distance. I find that a handy rule of thumb is "stay 30 seconds away from intercept": switch to map mode and mouse-over the intercept marker, which will give you a timer countdown to closest approach. Thrusting to slow yourself down will increase the time-until intercept. Just keep that at 30 seconds until your speed gets down to whatever you're comfortable with (I usually go for around 10-15 m/s), then switch back to camera view and you can eyeball it the rest of the way.

When you get really close, slow yourself to a stop, 0 relative velocity. You're now parked right next to the target-- if you got things lined up well up to this point, you'll be very close, just a few meters away, like this:

 

 

Step 4: Prepare to dock

Navigation tool: Navball and/or camera view
Control via: reaction wheels only

First, get roughly lined up. We need to get the docking ports at least approximately lined up (facing towards each other).

If possible, the easiest way to do this is to switch briefly to the target ship (using the [ ] keys) and rotate it so that it points its docking port towards your ship, then switch back and rotate your ship appropriately. This is a lot faster and easier than flying your ship around the target to get in the right spot, which is tedious.


(Sometimes that might not be an option, if it's not practical to rotate the target-- for example, if your target is a huge, massive, asymmetric space station with random stuff docked all over it. In that case you just gotta fly your ship to where it needs to be.)

Next, set your target and control-from to the two docking ports.

Right-click on the target docking port and choose "Set as Target":


Right-click on your own ship's docking port and choose "Control from Here":


Now, get your orientation precisely aligned. That is, you want the axis of your docking port and your target's to be precisely parallel. (They may be laterally offset from one another for now, but we'll deal with that next). There are a couple of ways to do this:

Option #1: Use a docking-alignment mod. My personal favorite is Navball Docking Alignment Indicator. It's very minimalistic, uses no screen real estate, stays out of my way when I don't need it. What it does is this: whenever your target is a docking port, it adds a red icon to the navball showing your alignment relative to it. When that red icon is perfectly centered in your navball cross-hairs, it means you're perfectly aligned for docking. So if you have this mod installed, all you have to do is rotate your ship to center that red icon. Your navball would then look like this:

...all you need to do is to rotate your ship to center the red icon in the navball crosshairs.

Option #2: Just eyeball the orientation. This is doable but less convenient. Not only do you generally have to monkey around with different camera angles, but it also becomes a royal pain in the dark, since you can't see what you're doing unless the ships are lit up. This is what I did for the first several months (and several hundred dockings) in KSP, until I got fed up and switched to option #1. Really, that mod ought to be part of the stock game, IMHO.

Either of the above two options will work. For the remainder of this discussion, I'll use screenshots that have the mod present, not only because that's how I do it when I dock, but also because it makes the screenshots much easier to understand.

Next, turn on fine-control mode. This is caps lock by default (on Windows machines; I think it may be different on Macs). Doing this will turn your control indicators at bottom-left from red to cyan, like this:

...The reason why you do this is described in another blog post, but what it boils down to is that it makes your RCS thrusters smarter so that it's easier to control your ship.

Next, activate RCS (press R). There, we finally get to use our thrusters!

 

Step 5: Dock!

Navigation tool: Navball and/or camera view
Control via: RCS thrusters

Okay, now the fun part.
Thrust gently prograde using your RCS thrusters until you get your speed up to 0.2 or, at most, 0.3 m/s. Slow slow slow. Your ship is now heading directly straight ahead. However, that's not quite right yet, since the target is offset to the side by a bit. We need to apply some lateral thrust in order to get us heading in the right direction.

Initially, your navball might look something like this:


How to read this:

• You're pointing in exactly the right direction: the red icon (from the mod I discuss above) is perfectly centered in the crosshairs, indicating that you're aligned correctly.
• Your position isn't quite right, because the target isn't directly in front of you. The is off to the left, instead of perfectly centered in the crosshairs where we want it.
• Your velocity isn't quite right, either-- the marker shows that you're moving up and rightwards as you drift forward, whereas your target is off to the left.

So now you need to use your RCS thrusters to correct that. Use your lateral thrust (IJKL for up, down, left, right) to nudge the marker to where it needs to be. You want to arrange it so that the marker is directly on a straight line between the marker and the center crosshairs, like this:

...What this means is that as you drift towards the target, you're also drifting sideways so that you're lining up with it. As you get closer, you will see the slide towards the center crosshairs. As it gets closer to the center, you can nudge the marker inwards, too (using RCS), still keeping it lined up:


When the marker reaches the center of the crosshairs, use RCS to center the marker there, too.


You're now all set up perfectly for docking:

• Centered red icon = you're facing the right way
• Centered = the target port is right in front of your port
• Centered = you're traveling directly towards it

Now all you have to do is just let it coast until docking completes.


Ta dah!

[VoidSquid]

Should be made a sticky post, as this is not only one of the most common and non-trivial questions but also one of the most excellent guides.

Edited November 15, 2019 by VoidSquid

[Space Nerd]

This is so helpful! I did my first manual docking after reading this!(always used mechjeb auto docking before that)

 

[Pecan]

On 11/17/2019 at 2:50 PM, Space Nerd said:

This is so helpful! I did my first manual docking after reading this!(always used mechjeb auto docking before that)

 

Did you use Navball Docking Alignment Indicator ?

There are, as my old Sergeant Major told me, no extra points for doing it the hard way - I'm just asking what you thought of the mod, if you used it.

Just for anyone who isn't aware, it's one I always recommend, as Snark does.

Edited November 18, 2019 by Pecan

[Space Nerd]

I never used that, but docking is easy to me even without that.

[RedWolfKerbal]

As I am in the habit of learning things as they become necessary, never seems to be the easiest approach, this is a great tutorial to find!

My story, lol:

I got the game shortly after PAX East (a lie really, had it for years and somehow never played it), and decided it was a game for me to get amazing at. Installed it and did the in-game tutorials, decided on Career mode because I prefer challenging things over gimme's. Ended the tutorials just before the science tutorial, yes i ended up regretting this and still have to revisit so that I can actually get a move on in the R&D Department.

So then I decided that my first big goal was Orbit. At the same time decided not to use the revert flight options every single time something went wrong, determined this to be a big headache when learning so decided to use it after all and plan for after I've learned more that I can add that difficulty. After a few hours I had finally learned enough about getting into orbit and tweaking my TWR that I was able to get a Kerbal into orbit. One small issue... I was then out of fuel. And I had left that flight and returned later to realize there was no reverting from this situation now, so he was stuck out there... forever unless I learned some things. So in learning these things I discovered that I hadn't know much at all about getting into orbit properly and had ended up there by chance lol. That being said, I had a rather high altitude polar orbit, as opposed to a nice equatorial one, and I had no idea how to control that aspect of the flight. Also learned that I had never learned about maneuvering nodes because I stopped doing the tutorials because I was too anxious to get to orbit...

Sooooo, enter the need to learn docking...

Well the last thing I want to do is be a stranded astronaut with no means of getting saved. So my mission became to save Jebediah from this life of lonely orbit. Starting watching some videos and reading the KSPedia while I was stuck away from my computer in hopes of being armed with the requisite knowledge to get Valetina to quickly retrieve are marooned fella. Well, in this journey for knowledge it discovered the fact that the EVA suits have their very own RCS. Eureka! A means of getting movement lol. Well I wanted to experiment, mainly because I saw someone do it on video, and see if i cant get ole Jeb back using his one means. Well, I still don't know if he would've died reentering the atmosphere, because he ran out of Monopropellant... and now, a few hundred km behind our forever orbiting craft, is poor Jebidiah. Far more uncomfortably stranded than he previous was.

So back to the Valentina Rescue Squad idea.  

Thought there were a few ways i could do this: prep a craft with a cabin that supports more than one crew (can't, not unlocked yet); get into orbit with the craft, and/or Jeb, and nudge them both radial in and retrograde and see where they fall (still an option, however it would be a highly skilled set of maneuvers and likely deathly for Jeb - I think the craft would be fine); or have an extra crew compartment for Jeb to stow away in after we rendezvous with him and get him to his ship. (this is what I am going to try)

Well I learned two things, maneuvering and meeting up with an orbiting craft is a pain; and the in game tutorial and my brain were not syncing up properly for me to learn enough to pull this off. I spent at least 2 hours a day for the past few days learning and trying to complete the docking tutorial and failing miserably. So now I feel that what I have learned form this tutorial may be that little bit extra I needed to pull it off.

What did I learn here that I hadn't in the in game tutorial? 

Well for starters, that both of the intercept nodes are important lol. I hadn't noticed that one orange was my intercept and the other orange was the targets intercept. Happy to know that now, the in game does try to convey this message however I didn't understand how it was conveying said message. Second, how to come about the approaching of the vessel, now granted this may be because I couldn't even get to this part in game yet but learning the NavBall tricks to line up all the markers properly will be extremely beneficial.

Well, hopefully before the weekend is over I can report that Jebidiah has made it home safely. Also hope that maybe you were entertained by my story, the friends I tell this story to usually find it pretty entertaining... how much of that is my tone and mannerisms I am unsure.

Oh and in the case that I was unclear of the overall intent of this entry... Thanks a ton for the tutorial

[RedWolfKerbal]

Alright so an update on Jeb...

I did manage to get the docking tutorial completed finally, man was it a fist pumping moment of pure excitement. However, things didn't go so well for Jeb. I couldn't get my craft into orbit with enough fuel to maneuver and pick him up. And after that I decided it was time for a new career mode, so i started that lol. I was a bit motivated to start over due to the fact that I wanted to start Twitch streaming the game and my plan was to make every moment I played of it available to watch. Granted I didn't realize retaining the videos for later viewing was a thing I had to setup, so the first 3-4 hours of it are not available. However, this career I decided to go with Airplanes pretty early on ( I am terrible at doing any of the below xx,xxxm tasks and I figured this would help.

Well it didn't go very well haha. If you want to watch some one fail every so miserably with airplane design, I've got you. Just check out Kinslayer125's videos haha. Once again thanks for the tutorial, if there is anything I learned from finally doing a successful dock, wait until you close the gap. For some reason I was trying to use RCS at like 15km out to make the approach closer. It's like golf, you setup the first maneuver to get it close and the second for the putt. Oh but you get RCS as a third. Also, it sucks not having more than just Prograde, Retrograde and Stabilize as SAS options. Guess I gotta work on getting more science.

[RedWolfKerbal]

https://clips.twitch.tv/GlamorousDeterminedPelicanCoolStoryBro

 

Able to try the tutorial a few days after the first and, aside from some silly things I forgot, I nailed it first try. 

[RedWolfKerbal]

Ok I'm back lol, managed to "speedrun" the docking tutorial. Dropped my time from 1 hour to a more respectable 27 minutes. 

 

Check out this video "Highlight: Kerbal Docking Tutorial Speedrun" http://www.twitch.tv/kinslayer125/v/575860847?sr=a&t=1s

[Wizard Kerbal]

I found that a lot of people launched space stations in one launch. I just taught myself how to dock, because i failed to do so during my first mun mission.

[AJ Milne]

Simply an excellent guide. And really solved an issue for me. I've this ambitious (for me) plan to do a major flotilla-type thing to the Jool system in a single transfer window (Y3-D270) in career mode now I've got the funds to put up a bunch of stuff at once -- like twenty vessels queued in Kerbin orbit for transfers, use a calendar/clock/reminder thing so I don't miss any (they're all scheduled to do the eject burn from Kerbin like hours apart over a period of some days), then transfer them all in coordinated fashion, to do a huge mission all at once. Buncha relays around all the moons and some big ones at the edge of the system to boost the signals, heavy landers for Laythe and Tylo, a miner/refiner thing working on Bop and Pol and keep refuelling the landers (I've got the Laythe one reuseable), some tugs and ferries for slinging crew and landers around, some tankers to transfer fuel into the inner system from the miner/refiner on the outer moons...

... and a space station, just outside Tylo's orbit, with lab for promoting crew.

Solved all the other bits, step by step, built stuff to work. The sticking point: the space station. Plan is to assemble stuff at right angles to its central axis, after it arrives in orbit, transfer it and some of the components separately, stick on some extra habitat modules, stuff like that. And while I've done lots of docking and recovery stuff before, it's always just been relatively simple nose-to-nose things. Always made it work, but it was always a bit of trial and error, save the game a lot, so on...

And when I started trying it in a scratch game, to do the really fiddly bits of putting the Jool station together, make sure everything worked, I couldn't use my usual approach... Can't just sling a space station around like you need to the way I do a simpler nose-to-nose rendezvous; you need to be able to fly the incoming ship a lot more delicately and precisely than I was used to, and get it all to line up from just that one side.

This guide, and that mod (I say, oh, yeah, get it) for working out the angle of the ports, that solved it. Very first attempt at gliding in the first habitat module, following this approach, it went just like the label says it does. I swear you could hear the magnets snap it on. Did the next to confirm it wasn't just dumb luck, and yep, this is how to do it, all right. Thanks so much.

Edited January 20, 2021 by AJ Milne
Typos

[Neptunium_69]

Fun Fact: When I docked for the first time, I didn't know that I docked because it was at night time. I just thought that my space station was destroyed during a crash because it disappeared. I time warped to the day to realize that I docked.

[darthgently]

16 minutes ago, Smart Boy said:

Fun Fact: When I docked for the first time, I didn't know that I docked because it was at night time. I just thought that my space station was destroyed during a crash because it disappeared. I time warped to the day to realize that I docked.

Orchestral Maneuvers in the Dark

[Dakitess]

Alleluia, finally a good docking tutorial ! I lost mine on an ancient tutorial, and was too lazy to rewrite it from scratch, knowing that there were probably people actually writing tuto how I do it myself AND with the same method ! This is so unusual to see the "active-retrograde-redirection" rather than the "kill velocity, accelerate toward the target, kill again, and forward again", which lead so many beginners to endless orbital drifting... 

So, yeah, it's not in french but it's easy enough to understand so that I can redirect people in need here