Trouble Matching Docking Velocities

[Mr Shifty]

Yeah, to elaborate, the only reason you match orbits with your target is to give yourself a good starting position. In fact, I almost never bother with this; I just try to get a close enough intercept, but it's a good starting condition when you're figuring out how to do it.

Rendezvous is defined as being in exactly the target's orbit at exactly the target's position. But you don't need to worry at all about matching the target's orbit during the rendezvous; the rendezvous procedure will accomplish that automatically. Specifically, if you're close to your target (within a kilometer or so) and you zero out your relative velocity, your orbits will be nearly identical. Let me repeat that; zero relative velocity when you're close to your target means your orbits are nearly identical. And again, zeroing out your relative velocity is as easy as pointing retrograde (assuming your Navball is in Target mode) and burning until your target velocity indicator at the top of the NavBall reads 0.0 m/s.

So you start out by matching your target's orbit. Once you've got a matched orbit, you need to catch up to , for example, you're orbiting 300 km behind your target. You need to catch up. To catch up, you need to go faster than your target. The only way to go faster is to change your orbit. To go faster, you have to make your orbit smaller and to go slower (if your target is behind you) you need to make your orbit larger. You should be able to see the closest-approach indicators get closer when you raise or lower your orbit appropriately.

[King Arthur]

I fly most of my rendezvous maneuvers on autopilot with MJ 2 now ever since starting a new save in 0.21, but back in 0.20 and MJ 1.9.8 (MJ back then didn't have a rendezvous autopilot!) I flew all my rendezvous manuevers manually by hand and managed to nail most of them once I got the basics down.

What I did was the following:

1. Align inclination/plane.

2. Get into a circular phasing orbit that is 20km +/- from my target's orbit depending on whether I am ahead or behind the target. If ahead, 20km higher; if behind, 20km below.

3. Close to within 200km of my target to prepare for setting up a Hohmann transfer (note I am still in my circular +/-20km phasing orbit).

4. Place and perform a Hohmann transfer at the appropriate point in my orbit via manuever nodes (I eyeballed this, only thing to do here was practice; also note that I am well past and closer than the 200km distance mark from my target now) such that the transfer places my closest approach with my target at 100m~500m (yes, I was precise about this).

5. Coast to my new apoaps or periaps that intercepts my target's orbit following Hohmann transfer burn.

6. When I am 2.5km out from my target (read: when the physics engine loads on my target!), I burn pro/retrograde relative to my target as appropriate to reduce my relative velocity to my target to 1/100 of my distance (ie: 2km out? 20m/s. 500m out? 5m/s).

6a. I continue reducing my velocity appropriately at 100m and then 10m distance intervals as I slowly close in on my target, I also performed midcourse corrections as neccesary with RCS and/or engines.

7. At roughly 100m out, I reduce relative velocity to 0 and then initiate my docking manuevers.

When I was in my last days playing 0.20, anxiously waiting for 0.21 to come out and also move up to MJ2, I was performing rendezvous manuevers that sometimes placed me <50~80m out when I had finished and had got the whole thing down to a routine.

I let MJ fly my rendezvous nowadays, but it feels confident to know that in dire times I can always take manual control and fly safe; and having learned all this myself, I can say with confidence that everyone can in fact learn to rendezvous if they invest honest time and effort into it.

EDIT: And if all else fails, have MechJeb plan and perform a rendezvous with a target. What MJ2 does is roughly what I was doing by hand in 0.20 except with more priority on lowering time spent rendezvousing rather than saving on fuel. MJ can teach you what matching inclinations is, what a Hohmann transfer is, what a phasing orbit is, and how you reduce relative velocity to zero better than any video or written tutorial can if you have an open mind and are willing to watch and learn from what it's doing.

Edited August 14, 2013 by King Arthur

[Mr Shifty]

No sir. I am talking about encounters at 400 meters or less. I will reiterate that my problem is not an issue of getting close enough to the target - it's a matter of killing the RVEL at the right time so as not to widen the distance (if too soon) or watch the target sail by into the distance (if too late). All the toying around with orbital arcs isn't answering the one sticking point for me in this whole thing. But I thank you for your assistance.

I actually don't kill my velocity totally until I'm about 30 meters from the target. Then I align for docking and start RCS translation. I slow down continuously as I approach so that my relative velocity in m/s is about 100x less than my distance from the target in meters. As I slow down, I'm always "pushing" my relative retrograde marker toward the anti-target marker. (To do this, draw an imaginary line from the anti-target marker through the retrograde marker and point your vessel at the other side of the retrograde marker on that line. When you burn, you should see the retrograde marker move away from your heading and (hopefully) toward the anti-target marker.

[HeadHunter67]

As for speeds? I'm talking, for instance, about going from a stable orbit at 80-100km (where one might refuel or wait for a window), to an orbit of 120-150km where one might want to dock with or set up a station.

Maybe my mistake was trying the method I've seen where the orbits are significantly apart (like 100:300km) so my RVEL is about 300 m/s. The problem I have is, when I tried to practice as you advised a pair of orbits that are only maybe 10km apart at most, I cannot manipulate the map screen or maneuver nodes effectively. If I zoom in close enough to see the difference between the orbits, I lose focus on what the planned maneuver will do. If I scroll out far enough to see its effects as I plan it (and you kind of need to), I can't actually manipulate the node, because as I said, if your pointer's off by a pixel it will skew the maneuver too much.

That's why I was trying orbits that were farther apart - because I could see what's going on.

I actually don't kill my velocity totally until I'm about 30 meters from the target. Then I align for docking and start RCS translation. I slow down continuously as I approach so that my relative velocity in m/s is about 100x less than my distance from the target in meters.

If I wait until 30 meters, it's too late - the target sails by and keeps going. I mean, how much later could one wait to start killing RVEL?

And I don't see how those two statements can be rectified to one another - at 30 meters, if you have 1% of the distance in velocity, you're only going 0.3 m/s. In other words, you were with the target all along.

Still not getting a "when" answer that would seem to work or make sense. I'm not trying to be obstinate.

Edited August 14, 2013 by HeadHunter67

[Mr Shifty]

You don't need maneuver nodes for rendezvous at all. And you only need the map screen to set up your phasing orbit establish your initial (20km or less) intercept.

[Anton P. Nym]

You don't need maneuver nodes for rendezvous at all. And you only need the map screen to set up your phasing orbit establish your initial (20km or less) intercept.

About the same here; I only use the nodes to set up the (rough) orbit match*, after that I just watch the map to see when the next encounter gets close enough. The Ap/Pe change and the RVEL kill I do by eye and Navball. (All hail Navball.)

-- Steve

* Particularly the inclination match; I just can't eyeball that to save my life and I lean on the node system's numerical readout to tell me when the nodes are O/NaN. I'm terrible at billiards/pool.

[HeadHunter67]

5. Coast to my new apoaps or periaps that intercepts my target's orbit following Hohmann transfer burn.

I guess my problem is, I just can't visualize this part right here. To my understanding, your new apoapsis and periapsis will never intersect the target's orbit, though it should cross at two points somewhere along the line. Whether your target will be at either of those points at the same time as you, seems like a matter of luck to me.

You don't need maneuver nodes for rendezvous at all. And you only need the map screen to set up your phasing orbit establish your initial (20km or less) intercept.

Hang on here? Am I understanding that the "best practice" for rendezvous is a blind guess? How in the world am I supposed to kow where the target is going to be by just blindly changing my velocity? Maybe "eyeballing it" works for those who already can do it, but I can't imagine how one can learn to do it that way without a lot of frustration and aggravating trial and error. Let me be clear that I'm not willing to give up fun to be good at a game - seems to defeat the whole purpose. I've already invested a lot of hours of annoyance at trying to prefect this, to the point where I've almost given up and said "%#$& rendezvous, let the robot do it!" Also, now that you can't just undo a mission, I'm not keen on killing dozens of Kerbals to get to that point.

I guess I'm not the kind of guy that learns well by reading something and being asked to imagine something I don't understand. Seems clear to anyone who's done it, but try explaining a waffle to someone who has no concept of a pancake. As for the video tutorials I've watched, it seems they've taught me incorrectly, or else I'd already be able to do it.

Edited August 14, 2013 by HeadHunter67

[King Arthur]

I guess my problem is, I just can't visualize this part right here. To my understanding, your new apoapsis and periapsis will never intersect the target's orbit, though it should cross at two points somewhere along the line. Whether your target will be at either of those points at the same time as you, seems like a matter of luck to me.

I guess I'm not the kind of guy that learns well by reading something and being asked to imagine something I don't understand. Seems clear to anyone who's done it, but try explaining a waffle to someone who has no concept of a pancake. As for the video tutorials I've watched, it seems they've taught me incorrectly, or else I'd already be able to do it.

Pictured is a Hohmann transfer that MJ calculated for me (I was too lazy to do it by hand ), with my ship orbiting at 150km and my target (a space station) orbiting at 300km, both circular and equatorial.

Once you perform the Hohmann transfer, your orbit will be roughly following the predicted orbit in the dashed line and you will notice that my orbit crosses paths with my target's orbit somewhere near my new apoapsis (if you were to start from a higher phasing orbit rather than the lower phasing orbit I am in this would be your periapsis instead). What I and MJ do following the Hohmann burn is that we coast to the new apoaps/peripas and then burn there to reduce relative velocity to the target, done right I (as well as MJ) can bring my ship to a stop very close to my target from where I can then move on to docking or whatever.

Edited August 14, 2013 by King Arthur
Typo fix. :P

[Mr Shifty]

Hang on here? Am I understanding that the "best practice" for rendezvous is a blind guess? How in the world am I supposed to kow where the target is going to be by just blindly changing my velocity? Maybe "eyeballing it" works for those who already can do it, but I can't imagine how one can learn to do it that way without a lot of frustration and aggravating trial and error. Let me be clear that I'm not willing to give up fun to be good at a game - seems to defeat the whole purpose. I've already invested a lot of hours of annoyance at trying to prefect this, to the point where I've almost given up and said "%#$& rendezvous, let the robot do it!" Also, now that you can't just undo a mission, I'm not keen on killing dozens of Kerbals to get to that point.

I guess I'm not the kind of guy that learns well by reading something and being asked to imagine something I don't understand. Seems clear to anyone who's done it, but try explaining a waffle to someone who has no concept of a pancake. As for the video tutorials I've watched, it seems they've taught me incorrectly, or else I'd already be able to do it.

If it would help, I can take some screenshots later this evening. It's possible to do the calculations for rendezvous (and they're actually not that hard), but like all things Kerbal that require pin-point precision, its easier to just fly the rendezvous, and you lose very little efficiency that way.

[HeadHunter67]

OK, the image helps a little (though it's kind of busy and the part you describe is hard for these old eyes to make out clearly), but I'm still not seeing how there's any guarantee the target will be there when you get there. What's to say it won't be on the other side of the world then? In which case, all you'll be doing is chasing each other around the orbit.

Am I missing something here that's obvious to veteran players?

If it would help, I can take some screenshots later this evening. It's possible to do the calculations for rendezvous (and they're actually not that hard), but like all things Kerbal that require pin-point precision, its easier to just fly the rendezvous, and you lose very little efficiency that way.

It sure would help, thanks - providing that the information I need is pretty clear to make out amidst all the rest. I wish there was a way to hide all the other orbital stuff that doesn't pertain to the target (other ships, debris orbits, etc).

[King Arthur]

I do apologize for the busy-ness of that image, I took that picture from my save game (only one that has ships flying) which was the quickest where I could demonstrate a Hohmann transfer. I did try and clear out as much clutter as I could.

Regarding the question of whether my target will be there, notice the "Intersect" blips near the apoaps of my Hohmann transfer and how it says "1.1km", that means that when I am at that point in my orbit my target will be 1.1km away from me. With dilligent placement of when to start the Hohmann transfer you can get that interception distance down to 100m or less.

[Anton P. Nym]

I guess my problem is, I just can't visualize this part right here. To my understanding, your new apoapsis and periapsis will never intersect the target's orbit, though it should cross at two points somewhere along the line.

I simplify this by making either the Ap or the Pe of my intercept orbit the same as the target's orbit; that way I know exactly where the encounter will be every time, at (or close enough to rendezvous with, anyway) the Ap/Pe.

Hang on here? Am I understanding that the "best practice" for rendezvous is a blind guess? How in the world am I supposed to kow where the target is going to be by just blindly changing my velocity?

Not a blind guess. (See above) And also not without reference to the map screen; once the target has been selected the map screen will show exactly where, when, and how close the next rendezvous opportunity will be and I watch that like a hawk. It's just that you don't have to plan out a maneuver node when you get a close encounter; you can toggle the Navball to "TARGET" mode, orient retrograde to your RVEL vector, and when you hit the encounter marker burn to ~0m/s. Then you have matched orbits and can work on closing with the target.

-- Steve

[HeadHunter67]

I simplify this by making either the Ap or the Pe of my intercept orbit the same as the target's orbit; that way I know exactly where the encounter will be every time, at (or close enough to rendezvous with, anyway) the Ap/Pe.

Please feel free to elaborate if I am wrong, but all that guarantees is that you will arrive at the same orbit as the target - but I am failing to see how it guarantees your target will be right there at that moment - especially if you're not even using maneuver nodes to see encounters.

How are you seeing an encounter in this situation? Or are you just flying around and around that ellipse until the serendipitous moment where the clockwork lines up that one time (which may mean a long, long time of watching)? I'm hearing a lot of "seat of the pants" advice, but what I need is something reliable - something that can be replicated reliably and if done properly, will work in a predictable way.

[stringyquark]

The part that took me the longest to wrap my head around is how the more you burn toward a target the further apart you get. While "chasing" a target, if you have to burn to hard to go toward it, the more you raise your orbit on the other side, this in turn can slow you down and make you go further apart. Reverse if you're in front and you burn to hard to slow down, you will lower your orbit and run away from your target. I found this by far the hardest part about rendezvous.

[HeadHunter67]

2. Get into a circular phasing orbit that is 20km +/- from my target's orbit depending on whether I am ahead or behind the target. If ahead, 20km higher; if behind, 20km below.

My question here is, how do you know if the target is "ahead" or "behind" if you haven't even established your orbit yet? (and a related question is:

"What's 'ahead' or 'behind' when launching from the ground to a rendezvous? Where's the cutoff?)

And if all else fails, have MechJeb plan and perform a rendezvous with a target. What MJ2 does is roughly what I was doing by hand in 0.20 except with more priority on lowering time spent rendezvousing rather than saving on fuel. MJ can teach you what matching inclinations is, what a Hohmann transfer is, what a phasing orbit is, and how you reduce relative velocity to zero better than any video or written tutorial can if you have an open mind and are willing to watch and learn from what it's doing.

I've learned enough from watching MJ that I'm willing to try it myself - but honestly, I'd submit MJ as the best way not to perform a task the "right" way. When I've tried rendezvous in MJ, it does some outrageous things - my docking target is at a 100km orbit, so it propels the docker to a 218km orbit or something crazy to intercept. And when killing RVEL, it kind of flops back and forth sometimes too quickly for me to understand what's going on. It does, however, have the advantage of being "hands-on" for me - I can alter camera views, switch between screens, etc - things I can't do when watching a video.

What I really need is a tutorial scenario for rendezvous - Blizzy78 made an excellent docking trainer that taught me how to dock in no time. I can dock at a port on the other side of a station, using the port on the back of my docking pod... no problem! But as for the getting there, I'm reading and seeing a lot of information that I'm having trouble rectifying into a coherent method.

Edited August 14, 2013 by HeadHunter67

[King Arthur]

My question here is, how do you know if the target is "ahead" or "behind" if you haven't even established your orbit yet?

Taking my picture above as an example, in that picture I am "behind" my target (the station of whose orbit is highlighted) because I am located physically behind my target relative to my direction of travel (in this and in most cases a counter-clockwise orbit).

To better visualize this, take a stick and hold it straight in front of you with arms outstretched. Pretend that the tip of the stick is your target, and that you are the orbiting body (such as Kerbin for example), and then spin yourself counter-clockwise. Now pretend that there are a lot of other ships and whatnot orbiting around you, anything that is to the right of the stick is "behind" your target and anything to the left of the stick is "ahead" of your target.

I've learned enough from watching MJ that I'm willing to try it myself - but honestly, I'd submit MJ as the best way not to perform a task the "right" way. When I've tried rendezvous in MJ, it does some outrageous things - my docking target is at a 100km orbit, so it propels the docker to a 218km orbit or something crazy to intercept. And when killing RVEL, it kind of flops back and forth sometimes too quickly for me to understand what's going on. It does, however, have the advantage of being "hands-on" for me - I can alter camera views, switch between screens, etc - things I can't do when watching a video.

What I really need is a tutorial scenario for rendezvous - Blizzy78 made an excellent docking trainer that taught me how to dock in no time. I can dock at a port on the other side of a station, using the port on the back of my docking pod... no problem! But as for the getting there, I'm reading and seeing a lot of information that I'm having trouble rectifying into a coherent method.

Amusingly enough, what MJ does there is in fact precisely what you need to do to get a rendezvous setup and accomplished.

The "218km" orbit you are propelled to is the phasing orbit and that is MJ choosing a different orbit from your target's orbit so that you and your target fly at different speeds, flying at different speeds means that you (and MJ) can then plan a Hohmann transfer where it is most appropriate to get a rendezvous. Your phasing orbit doesn't need to be 218km, that's just what MJ calculated would take the least amount of time overall to get you to a rendezvous with your target. The "+/-20km" phasing orbit I mentioned earlier was simply my take on the phasing orbit and both ways (among others) are equally legitimate in their executions.

The "flopping back and forth" that MJ does when killing relative velocity is basically MJ pointing your ship towards or against your direction of travel relative to your target, and is also what you need to do to reduce your relative velocity to zero.

While MJ might be inefficient with fuel consumption, its rendezvous autopilot is something that MJ highly excels at performing with great accuracy and safety, and everything MJ does there has a logical reason behind it. It might not appear to make much sense initially, but once you understand what MJ is doing there you'll realize that MJ is a lot smarter than it lets on.

Edited August 14, 2013 by King Arthur

[Anton P. Nym]

Please feel free to elaborate if I am wrong, but all that guarantees is that you will arrive at the same orbit as the target - but I am failing to see how it guarantees your target will be right there at that moment - especially if you're not even using maneuver nodes to see encounters.

How are you seeing an encounter in this situation? Or are you just flying around and around that ellipse until the serendipitous moment where the clockwork lines up that one time (which may mean a long, long time of watching)? I'm hearing a lot of "seat of the pants" advice, but what I need is something reliable - something that can be replicated reliably and if done properly, will work in a predictable way.

Selecting the vessel you want to rendezvous with as a target will show indicators for up to two encounters per orbit in Map mode. For each, one pointer will show where you will be when the encounter happens and one will show you where your target will be. Mousing over the pointer showing where you will be will show you the distance between the two pointers, to the nearest 0.1km. There's no guesswork involved; you'll know at least one full orbit ahead when the encounter you want will happen, exactly when and where and how far apart.

If the orbits aren't terribly different, the relative velocities will be low and thus burn times short enough that pointing retrograde to RVEL and burning at the encounter point until the RVEL reads 0 will be accurate enough for rendezvous... so no need to fuss with the Maneuver Node armatures. Indeed, not fussing with the maneuver nodes ends up easier (IMO) under those circumstances.

The only trying part in this is waiting multiple (sometimes many multiple, if I, er, mistime my launch) orbits for the map to show an encounter close enough, and we have Time Warp to help with that.

-- Steve

Edited August 14, 2013 by Anton P. Nym

[HeadHunter67]

Here's an example of what I was trying to say earlier. The interface makes it impossible for me to plan what should be a simple maneuver - even if we ignore for a moment that it can't distinguish between a planned maneuver that should already have been performed (target time T+) or one yet to come (target time T-).

Two ships - one at an 80km orbit, about to catch up to one at a 100km orbit. If I zoom out farther, there will be no differentiation between those rings; if I zoom in any further, I'll lose sight of the smaller orbit because of the planet. I can't work with this!. I don't see a way that I can plot anything useful in this screen - and going back to space view is like flying blind. How am I supposed to plan a maneuver or burn like this?

[HeadHunter67]

OK, so I managed to get a nice intercept - looked like 0.6km until I finished the burn, turned out to be 0.4 when done. Turned to begin a very slow braking when the target got within 2.5km, managed to close the distance until about 660m... then distance started increasing. No matter what icon I burned against, the distance increased. What do I do to close again? Even pointing straight at the target and burning only increased the distance.

This is exactly what I meant at the beginning - I can get close enough to wave before my target sails by, forever lost to me.

I could use Smart ASS to TGT+ or RVEL- but the whole point of the exercise is to do this myself. I'm so close but as they say, "A miss is as good as a mile"... or in the case of orbital maneuvers, a million meters.

Edited August 14, 2013 by HeadHunter67

[Anton P. Nym]

Two ships - one at an 80km orbit, about to catch up to one at a 100km orbit. If I zoom out farther, there will be no differentiation between those rings; if I zoom in any further, I'll lose sight of the smaller orbit because of the planet. I can't work with this!. I don't see a way that I can plot anything useful in this screen - and going back to space view is like flying blind. How am I supposed to plan a maneuver or burn like this?

Here's what I'd do in this case, assuming I'm in the craft at 80km and trying to rendezvous with the one at 100km. (Also assuming the Ascending and Descending Nodes up there indicate 0... I think that's the case here, but I'm so bad at gauging that...)

While in map mode I'd set the Navball to "ORBIT", orient prograde, and burn until the map indicates Ap of 100km to match the target's. (No maneuver node needed.) Once the two orbits have a point of contact you'll get the encounter markers, probably one at or very close to the tangential point, perhaps two equidistant ahead and behind that point.

I'd then wait a few orbits until the distance of an encounter shows less than 10km. Still in map mode, I'd set the Navball to "TARGET", wait again until I'm about a minute out from the encounter, then orient retrograde to the indicated velocity vector and track it. When I'm about 30 seconds out I look at the relative velocity indicated on the Navball to get a rough feel for how long the burn will need to be; the delta-V needed to match should be anywhere from a couple of meters per second to perhaps 30m/s. Even a Poodle or LV-909 can make that up over a few seconds of burn, so I'd start my burn at the indicated time without worrying about splitting the burn.

Reaching ~0m/s relative velocity at this point means I've matched orbits. I no longer have to worry about plotting Hohmann transfers and can use direct approaches, again without needing maneuver nodes because it's just matching relative velocity, orienting on the target, making a short burn, and matching velocity again. (Repeating as necessary, depending upon the orbit and how shaky my hands are.)

I have to sign off for the night now, but I'll answer any questions you have (if someone else hasn't already) tomorrow. Here's hoping this gets you to rendezvous.

-- Steve

[Mr Shifty]

Here's a bunch of screenshots of the rendezvous of a couple docking drones I threw into orbit with HyperEdit. The image descriptions have a bunch of text explaining each shot.

EDIT: Reached my imgur limit, so I can't host these shots anymore. PM me if you're necro-viewing this thread and need help.

Edited August 26, 2013 by Mr Shifty

[HeadHunter67]

Thanks, how do I view those large enough to make them out? Clicking each gives me about a 700x400 image. Can they be viewed larger? I know I can zoom by clicking on them but then I can't seem to view the annotations or scroll through.

I think I follow you up to the "approaching the target" image. Adding 115 m/s should surely cause your orbit to completely pass by something 20km away. Also, how do you "pull" the prograde marker onto the target marker (or "push" the retrograde onto the anti-target?) Please explain the method by which I can reliably align.

I must agree, however, that the Docking Alignment Indicator is a wonderful plugin. I don't strictly need it at that range, but it can sometimes be helpful in knowing which way to translate (those needles are the best addition to the mod yet). This time, when I tried, I mostly used the navball and the eyeball within 100-ish meters.

I thank you, and all the others who've offered advice, for your time and considerable patience. I think my knowledge and my technique are improving. I wouldn't dream of saying I've got it down like docking, but I am getting better. The most challenging thing about the close approach was because that entire portion happened on the night side. I had only the little target circle and my headlights to guide me. Once we got within about 20 meters, we crossed the terminator and thankfully, completed the docking in the light for a nice photo op.

Here's my second-ever successful attempt at manual docking. I used SmartASS a tiny bit (mostly once to align the docking target to the approach ship, and again to figure out what I needed to do when the distance started increasing again no matter what I tried).

Next stop... learning to land these bad boys at KSC!

Edited August 14, 2013 by HeadHunter67

[Mr Shifty]

Thanks, how do I view those large enough to make them out? Clicking each gives me about a 700x400 image. Can they be viewed larger? I know I can zoom by clicking on them but then I can't seem to view the annotations or scroll through.

Click the little gear in the upper right and choose "View the album on imgur"

I think I follow you up to the "approaching the target" image. Adding 115 m/s should surely cause your orbit to completely pass by something 20km away.

If I'm going 200 m/s, it takes 100 seconds to go 20km, that's usually plenty of time to turn around and slow down. And the 100x rule basically keeps the rendezvous 100 seconds away for the whole close. As I approach, I slow down to keep the target about 100 seconds away. My rendezvous usually take 5-10 minutes total. It's certainly possible to do it more slowly. The 100x rule gives me a not-too-fast-to-be-uncontrollable but not-too-slow-to-be-boring sweet spot. (Lately, I've actually been doing them 2-3 times faster -- keeping the high velocity until I'm under 5 km or so.)

Also, how do you "pull" the prograde marker onto the target marker (or "push" the retrograde onto the anti-target?) Please explain the method by which I can reliably align.

If you look at the "Getting quite close" image, you can see "pushing" pretty well. I've aligned the ship's heading so that the retrograde marker is between the heading and the anti-target marker; the three form a line with the retrograde marker in the middle. When I engage my engines, the retrograde marker will get "pushed" away from my heading, toward the anti-target marker. (This happens because of simple vector addition.) When the retrograde marker is directly on the anti-target marker then my prograde marker will also be directly on the pro-target maker and my vessel will be travelling directly toward the target.

The "Approaching the target" image shows "pulling", but it's harder to see because the prograde marker is close to the pro-target marker. For "pulling" prograde, you still want to set up the three markers (heading, prograde, pro-target) in a line, but this time you want the pro-target marker in the middle. When you fire the engines, the prograde marker will get "pulled" toward your heading and hopefully onto (or nearer) the pro-target marker.

Here's my second-ever successful attempt at manual docking. I used SmartASS a tiny bit (mostly once to align the docking target to the approach ship, and again to figure out what I needed to do when the distance started increasing again no matter what I tried).

Nicely done!

Edited August 14, 2013 by Mr Shifty

[luchelibre]

I believe I can put together a picture series that may be a bit easier and less involved to follow than the one above, even though it is good an accurate.

So we begin with your starting position. One ship at 80Km, and another at 100Km. The lower one is the one being controlled and is going to reach the higher one.

See the little blue ball about an inch ahead of my lower ship? That's where I'll start with the placement of my node. I'll be dragging it forward later, but I'm starting here.

Ok, node's up and ready to go.

All I've done here is drag the prograde marker on the node until the projected AP is about 100Km. Doesn't matter if nothing else matches up, just get that much done. For this simple maneuver, you won't need to touch the maneuver node again other than to drag it around the orbit line. Click and hold the node by its middle circle and drag it counterclockwise (the direction you're orbiting) around the blue orbit line.

This is what it looks like after dragging it ahead by about half the orbit. You'll notice as you do this that the projected rendezvous markers slowly get closer together as they circle ahead of the maneuver node.

See? Ok, now, what will likely happen is that you'll drag your node all the way around the orbit and get back to your ship. If you keep going, you'll notice that your markers go back to what they were when you started. This is because the markers only show what will happen on your current orbit. How to go farther? Use timewarp to orbit your ship farther along by an inch or two and then drag the node some more. You can do this all of this without getting rid of the node.

You'll notice my ships are farther along in their orbits. This allowed me to keep dragging the node far enough to get my markers very close together. Take note that it's the marker tips that must touch.

After timewarping to and doing the node burn, I then timewarped until my ships where near the markers.

My closest approach was going to be about 600 meters.

Notice I've got 'Target' in my navball. You bring that up by clicking that small space until it shows the word. You'll notice I'm pointed toward the negative relative velocity marker. Finally, you see I have to kill about 20m/s of velocity.

This is what I'm left with after a short low-power burn.

Now I'm pointed at the target ship marker. I'll make a short burn toward it. I've chosen to go about 10m/s toward it.

I've made my burn and have started to turn back toward the negative relative velocity marker.

Once I got close enough, I did a short burn against the negative velocity marker (NOT the one in the image, sorry). And that is what I'm left with. I think you can maneuver from there.

Edited August 14, 2013 by luchelibre
Really sorry about forgetting to include actually doing the node burn.

[HeadHunter67]

So you never actually did the burn from the maneuver node? Or was that left out?