Docking - SO close but no cigar

[GungaDin]

OK - I have 2 identical ships - both with ONLY a rear engine. I've gotten them to rendezvous - just maybe 50m apart and moving at almost the same speed.

In order switch to 'docking' mode I have to select the target ships docking port but I can't do that until I'm pretty damn close - can't mouse over it at 200M right?

Then - when I switch to docking mode I'm lost - I don't see how to 'translate' or anything. Is this all because I don't have small side thrusters? Is it better to step back and build a ship with side thrusters and try again or is it possible to dock with just one engine in the rear of each ship?

If I must have more thrusters - can someone recommend a good design pattern?

(I'm in career mode and don't want any mods...)

Thanks.

[federicoaa]

In order to translate you need RCS, maybe you need to wait until you can unlock them.

For your actual ships, just point them to each other and give some small relative speed, but it'll be hard without RCS.

[Kerba Fett]

To dock ships you'll need an RCS system as federicoaa mentioned and docking ports on each ship. When you place your RCS thrusters in the VAB you should turn on the center of mass indicator and place a ring of them in line with the COM. I like to use 4 way symmetry. 4 thrusters with 4 way control will allow you to translate in any direction and by placing them in line with the COM you don't get rotation when you translate. Normally your pods torque handles rotation. Do the balancing only on the stage that will be docking. Any boosters or transfer stages should be disconnected. Don't forget an RCS fuel tank.

Once you're in orbit and close, when you're in docking mode the spacebar switches between rotate and translate. You need to press R to turn on RCS and confirm that it lights up on the top of your navball.

When your navball is in target mode the yellow markers are not prograde and retrograde. They're your positive and negative relative velocity. What direction you're moving in relation to the other ship. If the yellow Rvel + marker is on the pink target marker you're going right at the other ship. You can adjust you're course to place this marker over the other ship by using wsad and Shift/CTRL just like the EVA pack.

To prevent apparent control reversal you can use the chase camera or place a marker on your ship during construction and roll the ship so the top points to the top of the screen.

Rather than trying to select a docking port at long range, I just drift till my closest approach and kill all of my relative velocity. This gives me plenty of time to select a docking port, control from my docking port and line up my approach.

If you do want to select the docking port from a long way out though, Place your camera between your ship and the target and zoom way out till you can see the target in the foreground. If you're lucky you've got an angle where you can click on the docking port,

You say you don't want mods. If you change your mind, look up the Docking Port Alignment tool by Navyfish. It shows a graphic of how your port is aligned with the target docking port and which way to thrust to get it in alignment. It's speed and distance readouts are way more accurate than the stock game.

The other I'd recommend is MechJeb. You don't get autopilots till later in the tech tree, but the Attitude Stability System that keeps you pointed in a particular direction is quite handy in docking operations. (and most others also)

[Vanamonde]

You can dock with only the main engines, but then, you COULD perform surgery with a hacksaw, too. GungaDin, dock mode is intended to be a player aid, but it's only an alternative, and you're not required to use it. I don't, because I don't want to keep two sets of steering reflexes in my head and switch back and forth between them.

[Kasuha]

Docking mode is more useful for rovers than for actual docking.

In normal mode, rotation is on WASDQE and translation is on HNIJKL.

In docking mode, you switch between translation and rotation (with SAS off) on WASD by pressing Space.

In both cases you need RCS to have the translation, as mentioned above.

[O-Doc]

Docking mode is for joystick users.

[Guest]

For some of them, anyway. I'm a HOTAS user and never really used docking mode. Thumbstick for translation, joystick+pedals for rotation and you're set. Fore and back are assigned to buttons on the throttle. If you have a HOTAS, then this is a really great setup.

[Geschosskopf]

Then - when I switch to docking mode I'm lost - I don't see how to 'translate' or anything. Is this all because I don't have small side thrusters? Is it better to step back and build a ship with side thrusters and try again or is it possible to dock with just one engine in the rear of each ship?

If I must have more thrusters - can someone recommend a good design pattern?

(I'm in career mode and don't want any mods...)

I have never used "docking mode" and don't even know how to engage it. I just use the default keys, WASD for rotation, IJKL for translation, and HN for forwards/backwards. I usually dock with both hands on the keyboard .

Anyway, rendezvousing is the hard part. From that point, it's just a matter of staring at your instruments and reacting to them as needed until you dock. There are essentially 3 phases to get from a close rendezvous to docking:

1. Rotate (pitch and yaw) the moving ship so it's parallel to the target, and also rolled as desired so it will be at the desired angle to the target once docked (so hatches are in line, protruding parts don't collide, etc.)
   
2. While keeping the moving ship parallel to the target, move it using translation until its axis lines up with the axis of the target ship.
   
3. While keeping the moving ship parallel and aligned to the target, translate forward (slowly) until the docking ports touch and voila!
   

As others have mentioned, you have to have RCS thrusters (and their fuel) to do the translating in step 2. Step 1 can be done with torque alone and if you're VERY careful, step 3 can be done with the main engines. If you're good, patient, and lucky, you can do the whole thing without RCS, but it's a lot easier if you have RCS.

So, RCS is mostly for translating. But if you don't put your RCS thrusters in the correct place, then their off-center thrust will cause your ship to rotate, screwing up what you accomplished in step 1 and making the whole process more difficult.

There are essentially 2 ways to place RCS thrusters. One is to use thrusters on each end of the ship, centered on the CoM, so their asymmetrical thrusts cancel out. The advantage here is you have 2 thrusters in each direction so you have more control authority. The other method is to use 1 set of thrusters placed directly on the CoM. No asymmetrical thrust, but less control authority.

Now, you don't want mods, but seriously, KSP has an utterly appalling and unrealistic lack of even basic in-game instrumentation. So I recommend the RCS Build Aid mod, which will let you put your RCS thrusters in the perfect positions so you get pure translation out of them, no unwanted rotation. This mod adds no parts, it just makes the CoM marker in the VAB more useful. It's still up to you to fly the ship using stock parts, but you can be assured that it will fly as you want it to without a lot of aggravating trial-and-error.

Another purely instrumentation mod you might consider is Navy Fish's Docking Port Alignment Indicator. This just gives you a pop-up display that does a way better job of showing you what's going on during the docking process. It's still up to you to actually make use of the information it presents by flying the ship yourself, but now you at least can see what's happening when you apply the various controls.

Edited February 10, 2014 by Geschosskopf

[GungaDin]

Thank you all so much for these great answers. SO much of this sim is the learning process and that would not be possible without a community of Kerbanauts willing to share their knowledge and develop new techniques.

So - a few more questions before I start welding on thrusters:

1 - I get that the placement of the RCS thrusters is critical - am I correct that these thrusters will only be fed fuel from a separate fuel tank and will not draw from the 'main' remaining fuel tank?

2 - To date I have done all of my maneuvering using the WASD keys, plus Q and E. How am I accomplishing that if I only have my main engine? What is yawing my ship?

3 - As a follow-on to question 2, once I have thrusters I will be able to use IJKL for translation and for and aft burns. That makes sense. So far the only way I have been able to slow down and not ram my target is to rotate my entire ship 180`. I guess the question here is just something I will have to try but if I'm in a docking phase, how do I keep track of fuel reserves that are coming from 2 different reserves of fuel?

Thanks again.

[Navy2k]

Hi,

1. RCS is a completly different type of fuel, its only 1 component: Monopropellant and that comes in special tanks.

2. You have 3 of those Control Moment Gyroscope in your Capsule for each axis. Plus you can add more, thy are in the control tab and have 3 Gyros each for every direction. But thay can only rotate your craft, and can't push it in any direction.

3. When correctly aligned you can slow down with "h" which will thrust "upwards" when you look at your rocket at the launchpad("n" is for acceleration). And for keeping track, just click resources on the right top so it stays visible.

Greetings

Ben

Edited February 10, 2014 by Navy2k

[Kasuha]

I get that the placement of the RCS thrusters is critical

It is not all that critical if you have enough torque to overcome unbalance. But if you get it extremely bad, it might be very hard to handle.

- am I correct that these thrusters will only be fed fuel from a separate fuel tank and will not draw from the 'main' remaining fuel tank?

RCS thrusters use Monopropellant. It is special fuel for RCS and it must be added to the ship in special containers. There's also a little monopropellant in each command pod but I doubt it's enough for inexperienced people.

2 - To date I have done all of my maneuvering using the WASD keys, plus Q and E. How am I accomplishing that if I only have my main engine? What is yawing my ship?

Without RCS the only thing you can do with WASDQE is to turn your ship around. Both the engine gimbal (if engine is burning) and built-in torque is used for it automatically.

3 - As a follow-on to question 2, once I have thrusters I will be able to use IJKL for translation and for and aft burns. That makes sense. So far the only way I have been able to slow down and not ram my target is to rotate my entire ship 180`. I guess the question here is just something I will have to try but if I'm in a docking phase, how do I keep track of fuel reserves that are coming from 2 different reserves of fuel?

There's a 'Resources' button in the upper right corner of the screen. Total available amount of fuel of each type can be seen in the table that pops up if you mouse over that button. Clicking on it will make the table permanent. It also allows to visualise fuel level in each fuel tank separately.

[GungaDin]

Got it. Now to build and practice I go! Oh - I forgot to ask earlier - is there a 'pause' key or a specific 'screenshot' key? This came up when I had my 2 spacecraft within a few feet of each other and could not figure out how to pause and say 'cheese'.

[Kerba Fett]

The escape key will pause the game, but it's not much good for screenshots while it's paused. If you're playing the steam version you can use F12 to save a screenshot for uploading to your steam library. If you're playing the non steam version, then F1 will take a screenshot and save it to the screenshots directory of your KSP folder. You can turn off the interface using F2 and I'm sure you've figured out that F4 toggles the onscreen labels. I find the labels really intrusive when docking.

[Max Grant]

Thank you all so much for these great answers. SO much of this sim is the learning process and that would not be possible without a community of Kerbanauts willing to share their knowledge and develop new techniques.

So - a few more questions before I start welding on thrusters:

1 - I get that the placement of the RCS thrusters is critical - am I correct that these thrusters will only be fed fuel from a separate fuel tank and will not draw from the 'main' remaining fuel tank?

On the lower left in the VAB are center of lift, mass, and thrust. Activate center of mass, and then use the tweakable feature to empty and fill your fuel tanks. That band where the yellow and black ball goes, is where your RCS goes. IMHO, if it is a really wide band, what I do is sometimes supplant the usual RCS with single-direction RCS thrusters at both ends, if the vehicle is long and the fuel will drastically shift the center of mass. So, instead of twisting from the middle, you're grabbing at both ends, so to speak.

2 - To date I have done all of my maneuvering using the WASD keys, plus Q and E. How am I accomplishing that if I only have my main engine? What is yawing my ship?

It's magic. I actually think we are allowed to use the "weight" of the Kerbals to turn the ship. IRL that isn't an option.

3 - As a follow-on to question 2, once I have thrusters I will be able to use IJKL for translation and for and aft burns. That makes sense. So far the only way I have been able to slow down and not ram my target is to rotate my entire ship 180`. I guess the question here is just something I will have to try but if I'm in a docking phase, how do I keep track of fuel reserves that are coming from 2 different reserves of fuel?

Thanks again.

If you use more than a few units of RCS to dock, your ship is too wobbly. Take for a small lander about 80 (two of the little spherical balls), for a larger vessel I stick four of the bigger RCS cans on it.

Also, if you're not using the Steam version of the game, F1 for screenshot. F2 turns off the HUD, I usually do that for pretty shots.

[Kasuha]

Got it. Now to build and practice I go! Oh - I forgot to ask earlier - is there a 'pause' key or a specific 'screenshot' key? This came up when I had my 2 spacecraft within a few feet of each other and could not figure out how to pause and say 'cheese'.

You can pause the game by pressing Esc.

To make screenshots, press F1. That will add a screenshot to the Screenshots subfolder of the game directory.

Most of keys to control the game and a lot of other info can be found on Wiki.

[m4rt14n]

For some of them, anyway. I'm a HOTAS user and never really used docking mode. Thumbstick for translation, joystick+pedals for rotation and you're set. Fore and back are assigned to buttons on the throttle. If you have a HOTAS, then this is a really great setup.

You're HOTAS joystick has a thumbstick? Or did you mean an 8-way hat? What brand/model is it? I'm looking to purchase a joystick.

[Geschosskopf]

So - a few more questions before I start welding on thrusters:

1 - I get that the placement of the RCS thrusters is critical - am I correct that these thrusters will only be fed fuel from a separate fuel tank and will not draw from the 'main' remaining fuel tank?

2 - To date I have done all of my maneuvering using the WASD keys, plus Q and E. How am I accomplishing that if I only have my main engine? What is yawing my ship?

3 - As a follow-on to question 2, once I have thrusters I will be able to use IJKL for translation and for and aft burns. That makes sense. So far the only way I have been able to slow down and not ram my target is to rotate my entire ship 180`. I guess the question here is just something I will have to try but if I'm in a docking phase, how do I keep track of fuel reserves that are coming from 2 different reserves of fuel?

1. RCS thrusters use monopropellant. Since 0.23, all capsules contain a small amount of this but you'll probably want/need some more. Mono tanks come in inline forms and in external spherical and oblong shapes. Usually, 4x of the spherical tanks will do you from launching a mondo lifter to getting home.

2. A and D are yaw, W and S are pitch, Q and E are roll. That's for rotation. For translation (this is NOT in docking mode, which I know nothing about and never use), J and L are left-right, I and K and up and down, and H and N are forwards and backwards. Without RCS, you have no IJKL functions, only WASD rotations and forwards. You can also go backwards by rotating the entire ship 180^ and running the main engine, which makes you accelerate backwards. Of course, you can't do this too close to the target ship or your exhaust will damage it.

3. Click on the Resources tab in the upper right corner to see how much of everything you have available and how fast you're using each resource. But in general, you'll approach the target and rotate backwards to it to stop nearby. So if your ship has main engines on 1 end and a docking port on the other, using the main engines to stop near the target will leave your engines pointing at the target and the docking port away from it. Thus, once you stop, the 1st thing you have to do is rotate 180^ so the docking port faces the target. After that, use RCS translation to get get lined up, then forward slowly to dock.