Rendevous and Docking Made Easy (with pictures)

This illustrated guide will teach you an easy technique to rendezvous and dock with another ship. It is both simple and relatively efficient.

Introduction

For your very first rendezvous, you'll want to make things as ideal and easy as possible. You will be meeting a ship in a circular, zero-inclination orbit. Once you get more comfortable with this, you can attempt more challenging rendezvous with ships in inclined and/or eccentric orbits. See hints at the end for how to do this.

Prerequisites

Before attempting to rendevous and dock, you should be familiar with the following:

• The ability to achieve a circular orbit .
  
• Knowledge of basic terms like apoapsis, periapsis, prograde and retrograde. For glossary, see this guide.
  
• Understanding of what the NavBall icons mean, and how to use maneuver nodes.

Knowledge of the NavBall is particularly important, because we'll be primarily using that for navigation. There is very little "winging it" by sight. See this page here for what the icons mean[wiki.kerbalspaceprogram.com].

Setting up

Design a rocket with a docking port, RCS and mono-propellent. 150 units of mono-propellent should allow you to make some mistakes and still rendezvous and dock successfully. You’ll want to make the upper stage small to make maneuvering and docking easy. In addition, since rendezvous and docking are delicate maneuvers, you’ll also want to use a small engine like the LV-909[wiki.kerbalspaceprogram.com] or the new O-10 Mono Propellant Engine[wiki.kerbalspaceprogram.com] in your upper stage. Your ship should be able to achieve Low Kerbin Orbit and still have around 200 m/s delta-v left.


In this example, I've decided to use O-10 engines along with a larger Mono Propellant tank. There is a shielded docking port at the top.


This will be the target ship and I've launched this ship into a circular orbit at about 154 km above Kerbin.

Step 1: Launch rendezvous ship

Return to the space center and get ready to launch the same design again. This will be the ship that will be performing the rendezvous.


Wait at the launch site until the target ship flies past above you, and then launch.


Place yourself in a circular orbit about 80-120km above Kerbin. Any altitude above the atmosphere (70km) and somewhat below your target should be fine.

Step 2: Match inclination

Open up the map, click on the target ship, and click “Set as Target”.


You should see ascending and descending nodes appear along with the degree of relative inclination.

It should be less than 10 degrees. If it’s more, it means that your first or second launch was not quite equatorial, though you still can do the rendezvous at the cost of more fuel. Create a maneuver node on the ascending or descending node that's closest in front you. You’ll need to burn normal (up or down) at the node. Create a maneuver that will reduce your relative inclination to 0.1 degrees or less and execute it. This maneuver should take very little Delta-V if your initial inclination is small.

Step 3: Perform the transfer maneuver

At this point, you should still be slightly behind your target. If not, you’ll need to wait a number of orbits until you are (you are travelling faster than your target, so eventually you'll go around and come up from behind again). Create a another maneuver node in front of your ship. Drag the prograde handle just enough such that the apoapsis of your orbit barely touches your target’s orbit (i.e. is tangent to). You should see one or two pairs of encounter markers appear. If two pairs appear, it means that you've gone too far prograde, and you are shooting past your target's orbit. You'll want to reduce the your apoapsis so that the two pairs of markers merge into one.


The top marker pointing downwards represents where your ship will be, while the bottom marker pointing upwards (and has the dotted line) represents where your target will be. Your goal will be to get these two markers right on top of each other.


If the marker indicates that you’ll be behind your target, you’ll want to drag your maneuver node counterclockwise so that it comes later. Remember that since we’re in a lower orbit, we’re moving faster than our target, so performing the maneuver later will give us more time to catch up.


If the marker indicates that you’ll be ahead of your target, drag the maneuver node clockwise so you burn earlier.


Drag the maneuver node back and forth until you get the intercept as close as possible, as can be seen above. Ideally, the separation should be less than 1km. Note that if you or your target’s orbit is not quite circular, you may also need to increase or decrease the amount you burn prograde so that the resulting orbit is again just touching the target’s orbit, and then readjust the location of the maneuver node so that the encounter markers line up again. This is why placing the both ships in circular orbits makes things much easier.

Save the game (f5) and perform the maneuver and delete the maneuver node. If you performed the maneuver with reasonable accuracy, your orbit should place you less than 10km at the closest approach. If not, reload (f9) and try the maneuver again.

Step 4: Getting even closer

Save the game and wait until you are about 1 minute until closest approach. Close your map, switch your navball to Target mode if it hasn't already automatically switched, and find the velocity retrograde (green) and target retrograde markers (magenta). These two markers are likely close to each other but not right on top of each other. When these two markers coincide, it means you are heading away from away from your target -- in other words, you’re heading toward your target.


In this picture, you see that what you want to do is “push” the green velocity retrograde marker toward the target retrograde marker by burning slightly away from the velocity retrograde.


This has the effect of both reducing your relative speed and changing the direction of travel so that you’re heading right at your target. As you approach, you should continue to make corrections and slow down further by burning directly on the green velocity retrograde marker.

A good rule of thumb is that you’ll want your relative velocity to be your distance to the target divided by 50 (i.e. at 5km, you want to be no faster than 100m/s) . Once you become more comfortable with rendezvous, you can approach faster.

Once you’re within 100m, your relative velocity should be 1-5 m/s. At this point, turn your ship 180 degrees to point directly at your target and activate your RCS (‘r’). Also, press Caps Lock to go into fine control mode mode. Use the ijkl keys to add lateral velocity to keep the green velocity prograde marker right on the target prograde marker. Use ‘h’ to speed up, and ‘n’ to slow down. Once you are within 30m, come to a stop by pointing directly at the velocity prograde maker and pressing 'n'.

Hint: Once your relative velocity is less than 1 m/s, it may be easier to slow down by moving the velocity marker around rather than trying to orient your ship to point at / against the velocity vector. The lateral translation keys 'j', 'l' will move it left or right on the NavBall, regardless of your orientation, while the vertical ones 'i', 'k' will move it up and down. Once you move the marker underneath where your ship is pointing, you can slow down and stop by pressing 'n'.

Step 5: Docking!

The next step is to point the two ships' docking ports at each other. Right click your ship's docking port and click "Control From Here". Right click the target ship's docking port and click "Set as Target". Use the NavBall to point directly at the target ship's docking port.

Switch to the other ship by pressing '[' or ']'. Activate RCS ('r') and also fine control mode (Caps Lock). Do the same thing on this ship. Now both of your docking ports should be pointed at each other like the picture below (note the NavBall).



Slowly begin moving toward the other ship by pressing 'h'. The key here is SLOWLY. Never move at more than 0.1 m/s until you feel comfortable with docking. At the same time, use the ijkl keys to laterally translate your ship so that the velocity prograde marker stays directly on the target prograde marker.

Press 'v' several times to switch to chase camera mode. You can swing the camera to the side or above/below in order to make sure your ship is aligned properly. However, keep an eye on the NavBall at all times and make sure you know where the prograde markers are.



If you find yourself not lined up properly, you can use the lateral translation keys (ijlk) to line yourself up. If you are having trouble with this, you can alternatively bring yourself to a complete stop (by pressing 'n' while pointed at the velocity prograde marker), and go into both ships and point them at each other as described above.

You should soon be docked. Congratulations!

Other tips

• The PreciseNode mod[forum.kerbalspaceprogram.com] lets you fine tune your maneuver nodes. This lets you easily get approaches as close as 0.1km. In addition, it has helpful shortcuts like placing a maneuver node right at the ascending or descending node.
  
• If you are above your target and want to dock, you’ll basically want to wait until you’re slightly ahead of your target, and you’ll need to burn retrograde in order to transfer to your target’s orbit.
  
• The technique described above is relatively efficient because you’re basically performing a Hohmann Transfer. After the initial prograde burn, you perform the second half of the transfer as you slow down relative to your target.
  
• If your target is on a highly inclined orbit, then instead of making an expensive inclination change, you’ll want to wait until your target’s orbit directly passes over your launch site. When you launch, you'll want to put yourself into an equally inclined orbit (set your target to help you do that). Note that since it’s unlikely that the target itself is also just passing overhead, once you achieve orbit, you’ll likely need to wait a lot longer to catch up to your target.
  
• If your target is very large and difficult to maneuver (like a space station), then docking is more challenging since you cannot point the docking port at your ship very easily. A docking alignment mod is very helpful in this case.
  
• If your target is on an eccentric orbit, then you’ll likely need to burn radially in addition to prograde or retrograde so that your resulting orbit is again just barely touching the target’s orbit. You may also need to make a series of maneuvers that get your orbit closer to your target’s eccentric orbit. In general, this is a challenging operation that requires skill and patience. PreciseNode is highly recommended.

[Ametlep]

sex

[Saltoo07_GFX]

i wish i saw it from my first hours

[Valdeka]

Hey, you stole my guide.
even though i made it just now and its way worse this is blatant thievery and you will be contacted by my lawyers within 2-3 business days.

[z 120908]

I have just learned to never try docking into a cargo bay its impossible.

[elaxitity]

easier guide: step 1: install mechjeb. step 2: open rendezvous autopilot. step 3: select the target and distance. step 4: enable autopilot. step tea: sit back and drink tea, it takes a while for encounter. step 5: while near the target, double click on the docking port you want to dock to (this will target it) step 6: open docking autopilot. step 7: on your craft, select "control from here" on the docking port. step 8: enable autopilot. step tea-b: sit back and drink tea again, after a while they will be docked. step docked: the guide is finished, you can stop reading and hopefully, the crafts are docked.

[m3]

i wish i found this guide a long time ago

[Ravenvál]

I have a way better idea.

alt+F12 opens a computer-assisted navigation and ship control interface (if you have the right pod), where you can navigate to "Set orbit" and select the ship you wish to rendezvous with, set your approximated engagement distance, and allow the navigation computer to do its trick. all you have to do is guide in your ship with RCS in docking mode and the dock ports will magnetically lock into each other when close enough

[Tallinu]

It might just be that the thrust from the RCS when in fine control mode is low enough (unless you hold the key down for a long time and it ramps up to higher levels) that your reaction wheels are strong enough to counteract it without any rotation ever becoming noticeable. Which, to be fair, may amount to the same thing in most cases, but perhaps not always.

[Empiro]

That's excellent advice. That feature wasn't available when this guide was written.

It's also important to note that if you're using the "Fine Control" mode, your RCS will automatically limit itself to avoid causing your craft to rotate when making translation movements.

[sir_frost]

what i am missing in this guide is the following tip
when designing your craft you can click the properties of the RCS thrusters and change activation toggle, if you turn rotation off on your RCS (and let the reaction wheels maintain rotation) then the craft will fly more stable, also when it comes to docking slow and steady is the way to go with minimal RCS.

if RCS is used to maintain rotation it can get stuck in a feedback loop( often when the RSC is off center)

if RCS only manage translation and your RCS throttle is low you can manage flying asymetric cafts with extreme precision.