Manual docking... having lots of issues.

[vindianajones]

Hi there. I've watched a couple of docking tutorials but they didn't seem to do me a whole lot of good. I'm trying to do completely manual docking (read: from launch to dock, no mechjeb or any other autopilot/assist tools). I'm completely hung up with a few points and I really need some help.

The part that I can do is the actual dock to dock maneuvering. If I let mechjeb get me into range of my target and put me at a reasonably similar speed, I can maneuver the craft using RCS/translation controls manually and get it docked up. I'm getting decent at it. My problems are in the previous stages.

My first problem is knowing where to time warp to so that the target is "over" the correct spot. I've tried lining it up right over the space center, but depending on the speed of my launch and how fast I reach apoapsis, it moves so much that it's never really there anymore, so I end up trying to manually do what mechjeb would do automatically.

Inclination changes: How do you do these? Are you supposed to burn in between the apoapsis and periapsis, or on one or the other? The thing I'm trying to dock with had a rough launch so it's at a weird inclination (like 6 degrees or so) and I try to match that, but with very little luck. I end up inclining the orbit too much on one side and not enough on the other side.

Reaching the target: I guess this is what they call a phasing orbit? I know if I'm behind the target I'm supposed to be going faster/be below it in altitude, and vice versa for being ahead, but I can't for the life of me figure out how to determine what a valid orbit is to actually reach the thing. Any tips for determining how the orbit should look relative to the target?

I know these are probably basic/stupid questions, but even after watching multiple guides I'm having a ton of trouble. If I can manage to get the target within visible range and I'm not going way too fast, I can almost certainly manually fly the vessel into place and dock it, but the whole "getting there" part just has me stumped.

[Ben Kerman]

Do you even know how to use maneuver nodes? Unless you are an orbital maneuvering master you won't really get far without them.

If you don't know this guy yet, you are missing something, he does some of the best KSP videos and also good tutorials: http://www.youtube.com/user/szyzyg

Here is a tutorial about really basic stuff (including orbital maneuvering):

And here a tutorial especially about docking:

Hope you haven't watched those tutorials already.

[vindianajones]

Yes... I know how to use a maneuver node, I just can't figure out where and how to configure these nodes to do inclination and orbital changes that actually get me to the target. I mess around with them and they never really put me in a place where I should be. I thought I explained it sufficiently, but use of maneuver nodes is not my problem, it's how to actually coordinate when and how to operate the nodes so that my ship reaches the target at the correct angle/speed to start docking.

[Temstar]

The part that I can do is the actual dock to dock maneuvering. If I let mechjeb get me into range of my target and put me at a reasonably similar speed, I can maneuver the craft using RCS/translation controls manually and get it docked up. I'm getting decent at it. My problems are in the previous stages.

Good, for most people they actually consider this the hard part. If you got a handle on this the first part, the rendezvous will be pretty simple.

My first problem is knowing where to time warp to so that the target is "over" the correct spot. I've tried lining it up right over the space center, but depending on the speed of my launch and how fast I reach apoapsis, it moves so much that it's never really there anymore, so I end up trying to manually do what mechjeb would do automatically.

Well to be honest, you don't really need to know it that well. You need to launch sometime before the target overflies KSC. Generally a climb to orbit for a fuel efficient ascent is about 4 minutes, not including coasting to apapsis. For LKO depending on the exact altitude you generally want to launch when your target is over the desert peninsula to the continents west of KSC. But don't sweet it - if you reach orbit and your target is within 100km of you you're already in business. I've done countless docking and only three times I managed to get a "hole in one" where I arrived at AP and the target was right there.

Anyway so you're in orbit somewhat close to your target. What you need to do is click on the target until a pop up box comes up that says "set X as target", do this. Once you do this the following steps are trivial:

Inclination changes: How do you do these?

Simple. Once you have your target set you will see two points on your orbit called "ascending node" and "descending node" and a degree on them. These two nodes are the points where your target and your orbit cross. What you want to do is to reduce the inclination difference between the target and you to zero degrees. To do this you simply burn anti-normal at an ascending node or normal at descending node.

Reaching the target: I guess this is what they call a phasing orbit? I know if I'm behind the target I'm supposed to be going faster/be below it in altitude, and vice versa for being ahead, but I can't for the life of me figure out how to determine what a valid orbit is to actually reach the thing. Any tips for determining how the orbit should look relative to the target?

This is simple once you have your target set too. So you already know that by going into a lower orbit you catch up and if you go to higher orbit you slow down. You notice on your orbit you have either one or two points called "closest approach". What you want to do is reduce at least one of them to as close to 0m as possible (but anything under 1km is close enough for docking via pure visual). Assuming you've already matched inclination with target, if you're ahead of target you burn prograde you will see that the "separation" value at these closest approach points reduce, visa visa for if you're behind the target. Simply keep burning until separation at closet approach is under 1km and warp to that point and you will be in position for final docking approach.

Note that if the separation between your target and yourself is too great you might want to do a prograde/retrograde burn without trying to reduce closest approach to zero. What happen is then with each orbit your get closer and closer to your target and the game will recompute the closet approach for you. Once the separation is within a small distance (say 30km), do the above to setup the encounter.

[vindianajones]

Thanks a lot. That's exactly what I was looking for. I'll give these tips a shot when I get home. I guess things are a bit easier for me to understand when explained via text rather than trying to follow along with a tutorial video.

[Morzak]

Yes... I know how to use a maneuver node, I just can't figure out where and how to configure these nodes to do inclination and orbital changes that actually get me to the target. I mess around with them and they never really put me in a place where I should be. I thought I explained it sufficiently, but use of maneuver nodes is not my problem, it's how to actually coordinate when and how to operate the nodes so that my ship reaches the target at the correct angle/speed to start docking.

1. The timing for launch is a bit tricky, with Kerbal Engineer Redux you can display distance to target, wait until this is around 500-400km away and then launch, this only applies for LKO at a 90 degrees heading (aquatorial orbit) (thanks to Scott Manley).

2. After launch you should get a decent approach at apoapsis, change your navball relation to Target, and start burning retrograde to kill all velocity in relation to the target. then you can start the approach (just burn a towards the target, I wouldn't go faster then 10 m/s under 1km).

3. If you missed the target with the launch, you have to check if the target is infront or behind. if it's behind leave, push you're Periapsis to be higher then the targets orbit (it becomes the new Apoapsis). a few KM should be enough. Warp and check after one revoluton how much closer the approach becomes and continue warping until you get a decent approach.

If the target is infront, keep Apoapsis on targets orbit and leave the Periapsis a few kilometer below the targets orbit.

If you're inclination is of (more then 0.5) you can adjust it on the Ascending or descending note (just set a node and pull normal/antinormal until inclination is around 0).

I hope this helps a bit, I get good approaches but I suck at the actual docking part.

[Blackstar]

Simple. Once you have your target set you will see two points on your orbit called "ascending node" and "descending node" and a degree on them. These two nodes are the points where your target and your orbit cross. What you want to do is to reduce the inclination difference between the target and you to zero degrees. To do this you simply burn anti-normal at an ascending node or normal at descending node.

(to vindianajones) To do this with maneuver nodes, just add one at the ascending/descending node, whichever is closer. Rotate the view and drag the pink handles up or down to align the orbits until the ascending and descending nodes rotate 90 degrees from where they are. You'll know you're doing it right when the AN/DN markers start to move very fast and you have to use a light touch on the maneuver node handles to keep them under control. Hovering over one should show an inclination of either 0 or NaN degrees. The blue marker on the navball will then show you exactly which way to burn and when.

So you already know that by going into a lower orbit you catch up and if you go to higher orbit you slow down.

Somewhat of a tangent, but I find it delightfully counter-intuitive that if you're on the same orbit as your target but "behind" them, turning retrograde and burning away from the target will cause you to eventually catch up.

[Ben Kerman]

(to vindianajones) To do this with maneuver nodes, just add one at the ascending/descending node, whichever is closer. Rotate the view and drag the pink handles up or down to align the orbits until the ascending and descending nodes rotate 90 degrees from where they are. You'll know you're doing it right when the AN/DN markers start to move very fast and you have to use a light touch on the maneuver node handles to keep them under control. Hovering over one should show an inclination of either 0 or NaN degrees. The blue marker on the navball will then show you exactly which way to burn and when.

[also to vindianajones] Note though that the maneuver note doesn't take into account that your Normal/Antinormal (burning directions for incl. change) also change along with your inclination. If you don't correct that on large inclination changes it can mess up your orbits pretty badly.

If you have MechJeb installed you can let it point at Normal/Antinormal. If you don't have MJ try pointing your ship just in the middle between pro- and retrograde (you know you're doing it right when your AP/PE only change slightly).

Somewhat of a tangent, but I find it delightfully counter-intuitive that if you're on the same orbit as your target but "behind" them, turning retrograde and burning away from the target will cause you to eventually catch up.

Well, it may be counterintuitive, but that's how physics work.