Docking: How do I get closer?

[Skorpychan]

Rendezvous, I can understand now. I figured out the navball markers for it, and got within 500m of the target. The question is, how do I get closer?

No matter which way I burn on the pink markers, it pushes me further away.

Do I just burn straight for the target, or what?

Also, how hard is it to do a direct ascent return from Duna, with enough fuel to get back to Kerbin? Because this docking lark is hard, and I want to land kerbals NOW, not next year when I figure it out.

Of course, I could always just install mechjeb, but I feel that's cheating.

Edited December 7, 2013 by Skorpychan

[Hodo]

Ok I had a problem like this when I first started docking also. When you get within 500m switch to RCS transitioning. I like to slow down at 500m to 5m/s and maintain that until I am within 50m, then I slow to 2m/s until I am with in 15m, then I slow to .2m/s for final docking.

I prefer not to switch to docking mode, it is a bit funky, I prefer to use the transition keys H=forward, N=back, J=left, L=Right, K=down, I=up. A simple plugin that REALLY helps is Navyfish's Docking alignment tool. It doesn't control anything just gives you a handy docking alignment indicator box that is so easy to use.

[Tex_NL]

Try this in-game tutorial: http://forum.kerbalspaceprogram.com/threads/41851-0-22-0-Docking-Tutorial-1-1-1

Or just search the forum and/or youtube. There are literally dozens of topics about this.

[Kasuha]

If you got that close and already killed your relative velocity, i.e. your distance is not changing rapidly (burn towards retrograde marker if you didn't), then the next phase starts by zooming on your target (without switching ships), right-clicking on the docking port on which you want to dock, and selecting it as target. Also switch to chase camera (usually the V key). This way you can aim your ship exactly in the direction you want to get on either side of your target or directly to it. Then you can gain required speed by short burn or by using RCS. At 500 m I would probably still use normal engines, especially if your ship is equipped with retrograde engines to which you can switch to brake when you get closer (because turning around at such close distances may be dangerous).

The docking is no different than hunting navball markers at close rendezvous, if you're oriented the right direction, just keep your prograde marker on the target marker and watch your relative speed to not get too close too fast.

[Monger]

No matter which way I burn on the pink markers, it pushes me further away.

Do I just burn straight for the target, or what?

Basically yes. Just make sure that your relative speed is 0 m/s at some point, otherwise it will get complicated. Also, make sure you are in translation mode, and your RCS thrusters are set symmetrically.

In my experience, most docking problems are caused by the ship design. Try to practice with the simplest and smallest craft imaginable.

Also, how hard is it to do a direct ascent return from Duna, with enough fuel to get back to Kerbin? Because this docking lark is hard, and I want to land kerbals NOW, not next year when I figure it out.

At least a lot harder than docking. Although you need a little less thrust for escape velocity from Duna than for Kerbin, it's still a lot. The problem is: landing a multistage ship is far from easy, and launching with a single stage into orbit is really hard.

Or in other words: the less weight you drop down, the less you have to pick up later.

[LtHeckard]

You should set the Docking Port as target, and then whenever you reach the closest point in between the two ships you're trying to dock, you need to switch to Target speed on your nav ball, and slow down until you're moving less than 1 M/PS, after that you should slowly burn towards your object. you'll gradually get closer and closer, when you reach the object, slow down until you're not moving at all relative to the object you're docking with. using the I J K L H N keys to control your RCS Thrusters, you can easily dock with just those. It will also aid you in docking if the object you're trying to dock to is facing you.

[Soda Popinski]

Make sure you're looking at the correct pink marker. The circle is towards, the triangle thingy is away.

Once you're moving towards (make sure ship is targeted, and your not on orbit or surface), use RCS to translate the center the grow circle on the pink circle.

[Psycix]

A very foolproof and perhaps the most easy way to do it:

1 Equalize velocity

Set the navball to 'target' mode

Burn on the retrograde marker until relative velocity is (about) 0.

2 Approach

Bun straight to your target (pink marker with circle)

3 Repeat

When close and about to zip past it, go back to 1, equalize velocities, and approach again. Rinse and repeat.

This is not the most fuel efficient way to do it, but it works just fine and the total delta V is not that much anyway.

If you understand how the navball markers work, you can try to keep your prograde on the target marker to compensate for the orbital drift (be it with RCS translation or main engines) so that you approach in 1 go.

Even better is to use the map view and create a closest approach from there using a maneuver node. With careful tuning it is possible to set up a <100 meter rendezvous from the other side of orbit, but it can be very difficult to set this up.

[Specialist290]

The important bit for the final approach is to pay attention to where the pink target marker and the yellow prograde velocity marker are in relation to one another. If you have the yellow marker centered on the pink marker, that means you're heading straight for your target. With a little practice, you can learn to "steer" the yellow marker around the navball to move in the direction you want.

[Monkeh]

I very nearly got to Duna and back without docking. It was badly built in the last stages. My bad. Check out my blog post if you can be bothered. Might help you out some. http://forum.kerbalspaceprogram.com/threads/60009-The-harsh-realities-of-engineering-Home-Sweet-Home-Mk2-To-Duna-and-back

Edited December 7, 2013 by Monkeh

[lajoswinkler]

You need to set your view to chase mode and then, using your right mouse button, drag the camera so that you're looking at your vehicle's rear end. Then you switch to docking mode, activate RCS and use W,A,S,D, right shift and ctrl keys to move around. At that point it becomes very intuitive and you don't need to watch your navigational ball all the time. When you're <50 metres from the target, you kill your relative velocity and use the ball and RCS keys to position the yellow prograde marker into the pink target marker. <1 m/s approach is convenient.

Compared to rendezvous, this is really easy.

[LethalDose]

Question to the OP:

When you say you can rendezvous within 500 m, is that stable? Meaning, are you STAYING at 500m with a relative velocity of < 1 m/s?

If you aren't able to get close and kill your V-relative, that's a different problem than not being able to approach.

[Soda Popinski]

Not sure how you feel about mods, but I highly recommend Dock Alignment Indicator. It seems silly to me to line up docking by eye from outside. Thus is a realistic and effective way to dock once you're within a few dozen meters.

[Skorpychan]

In my experience, most docking problems are caused by the ship design. Try to practice with the simplest and smallest craft imaginable.

Already got that worked out. My docking test ship is basically a fuel tank, an engine, RCS stuff, and a probe core.

Question to the OP:

When you say you can rendezvous within 500 m, is that stable? Meaning, are you STAYING at 500m with a relative velocity of < 1 m/s?

If you aren't able to get close and kill your V-relative, that's a different problem than not being able to approach.

Mostly stable. I got to about 700m stable, but can't get it to STAY closer. I get closer, then killing my velocity pushes me away again, or I left it too late.

I broke down and installed mechjeb, and I learned a lot from watching it do it's thing. I think I'm just gonna have to have mechjeb do it, then do it myself, and continue until I can reliably do it myself.

Thanks for the advice and help, people!

[LethalDose]

If you're stable (Vrel < 1m/s), then yeah, you just thrust AT the target with pink markers.

BUT if you're not getting the Vrel down to 0, which sounds like your problem, then that advice won't do you any good.

To get your Vrel down, you need to burn at the points on the NavBall that mark target prograde or retrograde, NOT the points that mark the target (which I think is what some posters here have suggested). If you're Vrel isn't already zeroed out, then thrusting at the pink target marker will do exactly what you're describing: Cause your Vrel to increase and fly past the target.

In fact, the reason that you want to thrust at the pink markers on your approach, is to line up the position marker WITH the prograde marker. This is just WAY easier to do when you zero out your Vrel first.

If you still want to try it the "old fashioned way", try burning towards the retrograde marker to reduce Vrel next time you want to dock, and then approach the target the way people have recommended.

[thereaverofdarkness]

If you're only 500m away, you probably shouldn't be using your navball. If you do use your navball, you want to make the green circle go over the pink circle. Thrust at the green x to stop. Also make sure your navball is set to 'target', and not 'orbit' or 'surface'. Click on where it says orbit or surface to change it.