Multi-point Docking

[espm400]

I posted this in a similar thread last night, but given that the OP was suggesting parts, it got moved. It basically was two points:

First, for those of you unfamiliar with how to incorporate multi-port designs into your spacecraft, here's a tutorial that helped me out loads. It just shows you how to circumvent the parent-child part tree system in a manner that just forces the other docking nodes to dock while still on the launchpad.

Second, unless you're a total mod purist and don't want any, I would suggest at least taking the two quad-couplers from this mod:

http://kerbalspaceprogram.com/half-meter-parts-and-other-useless-crap-r4-2/

I use the quad-couplers simply because they allow docking at 90* angles so I end up with cleaner designs. The mod has a bunch of really useful small diameter parts, although some of the batteries and a few of the other parts are quite over-powered and as such I have removed. The structural parts are great though.

Hope this helps

EDIT: Gimme a couple hours and I'll up a few example pics. I recently installed 'Deadly Re-entry' and 'Ioncross Crew Support,' so I also ditched most of my old designs and started a new save. So far I only have my RemoteTech coms satellites up.

Edited July 3, 2013 by espm400

[OUScooby]

Correct me if I'm wrong, but it's one parent one child part, isn't it? It may look like those are both connected, but they're not. Somewhere in that loop is a disconnect. Which is why the stations you see are all one to one.

What I've found is that multiple ports will dock together securely, but only one dock will cross feed fuel. My theory is that the magnetic force of the docking ports will hold multiple docking ports together, but because of the parent child build structure only one will be 'truly' docked and will cross feed fuel.

[Starwaster]

What I've found is that multiple ports will dock together securely, but only one dock will cross feed fuel. My theory is that the magnetic force of the docking ports will hold multiple docking ports together, but because of the parent child build structure only one will be 'truly' docked and will cross feed fuel.

Actually I've looked at the craft data in my persistence files for a particularly tricky ship. The Transplanetary ship + 4 docked tankers from kerbalspaceprogram.com. It has a core ship with docking ports fore and aft and four tanker ships that connect to it. A serious PITA to line up but once they are docked, I checked out the docking port nodes and all eight ports were properly linked to the right targets. (even though the aft ports were off a few centimeters)

[Sirrobert]

I found another problem while experimenting with docks. I'm trying to see what surfaces the actual docks will fit on.

In my contraption I'm trying to drop a module with a dock on it's bottom onto the rig that has a dock waiting right underneath the module. The problem is that the top part just stays gray when I place it in the editor, and when I launch it... disappears. See my included pics to see what I mean.

(Test Rig 1)

(Test Rig 2)

Edit:

Same with this approach. I feel like I'm missing something painfully obvious about the game here... are there some ways in which parts just don't want to click into place? How do I get these greyed out parts to join with my construction?

(Test Rig 3)

There are still no docking ports in those pictures

[Blackstar]

One thing I have noticed is that multiple pieces docked together decreases performance in a non-linear fashion. The more docking connections you have, the worse it gets when you add a new one.

I had assembled a ~200 part space station in orbit made up of 27 sections docked together, most of which were double orange fuel tanks that couldn't all be reasonably launched at once. The framerate was choppy even in time warp, and approaching it with a ship rendered things almost unplayable.

I decided to do a minor cheat and replaced the station in orbit with the exact same one, except as a single "ship" with all the connecting docking ports removed. After that it was smooth as silk.

[Tiron]

I found another problem while experimenting with docks. I'm trying to see what surfaces the actual docks will fit on.

In my contraption I'm trying to drop a module with a dock on it's bottom onto the rig that has a dock waiting right underneath the module. The problem is that the top part just stays gray when I place it in the editor, and when I launch it... disappears. See my included pics to see what I mean.

(Test Rig 1)

(Test Rig 2)

Edit:

Same with this approach. I feel like I'm missing something painfully obvious about the game here... are there some ways in which parts just don't want to click into place? How do I get these greyed out parts to join with my construction?

(Test Rig 3)

Test Rig 1+2: The hubmax parts have a weird issue where they'll only work properly if one particular node is used as the parent node. The rest of them result in it sitting there greyed out like that.

Test Rig 3: You can't do this. The ships are built as a tree structure, each part can only have one parent. You can't make circular or square structures in the VAB, only Linear, branching ones. You can get around it by using the multi-docking feature, but only if you use actual docking PORTS.

Docking ports are separate parts that have to be added on. They're called 'Clamp-o-Tron's, and come in three sizes. If you use pairs of ports, you can create the kind of structure you're going for. It'll still only actually be connected in the VAB on one side, but the other side will form a physical connection when it finishes loading. You could achieve the same effect in a non-removable form by using a strut to connect the unconnected joint.

[PTNLemay]

There are still no docking ports in those pictures

I was planning on adding them in latter, I wanted to first try and setup a frame-work of girders and nodes, then add some docking ports later. I actually managed to get a working prototype, eventually... (Rig Success) but those girders and nodes seem to be VERY non-cooperative. Half the time it seems like they just won't click into place, they stay "greyed out". At first I thought it was because I was making my structure too broad and that as the girders moved further away from the command pod they were less likely to connect... but at one point I started getting grey girders when I was still just starting off. I had all of 6 pieces on the contraption and it started being difficult.

Test Rig 1+2: The hubmax parts have a weird issue where they'll only work properly if one particular node is used as the parent node. The rest of them result in it sitting there greyed out like that.

So I just have to rotate the nodes until they hit the right spot? Edited July 3, 2013 by PTNLemay

[espm400]

What I've found is that multiple ports will dock together securely, but only one dock will cross feed fuel. My theory is that the magnetic force of the docking ports will hold multiple docking ports together, but because of the parent child build structure only one will be 'truly' docked and will cross feed fuel.

I'm not trying to be a dick, but I'll probably come off as one (sorry, I woke up literally two minutes ago), but it really bugs me when people don't actually read the thread before posting a response. Especially when the solution to the problem is in the post directly previous to the one being made. Honestly, watch the video in my post right above yours. It should solve all of your problems.

[Tiron]

I was planning on adding them in latter, I wanted to first try and setup a frame-work of girders and nodes, then add some docking ports later. I actually managed to get a working prototype, eventually... (Rig Success) but those girders and nodes seem to be VERY non-cooperative. Half the time it seems like they just won't click into place, they stay "greyed out". At first I thought it was because I was making my structure too broad and that as the girders moved further away from the command pod they were less likely to connect... but at one point I started getting grey girders when I was still just starting off. I had all of 6 pieces on the contraption and it started being difficult.

So I just have to rotate the nodes until they hit the right spot?

Eyup. It's a very weird bug.

[OUScooby]

I'm not trying to be a dick, but I'll probably come off as one (sorry, I woke up literally two minutes ago), but it really bugs me when people don't actually read the thread before posting a response. Especially when the solution to the problem is in the post directly previous to the one being made. Honestly, watch the video in my post right above yours. It should solve all of your problems.

Perhaps you should have had your morning coffee first and then read my post. I'm not having any problems with multiport docking myself, like I said they will dock together securely. And your video only addresses build multidocks in the VAB, I was actually talking about when docking in orbit.

[espm400]

Perhaps you should have had your morning coffee first and then read my post. I'm not having any problems with multiport docking myself, like I said they will dock together securely. And your video only addresses build multidocks in the VAB, I was actually talking about when docking in orbit.

Perhaps I'm misunderstanding something here. Are you referring to having problems with multiple ports on the bi/tri/quad-couplers or the six port cube? Either way I've never experienced the lack of cross-feeding with the six-port, and since I started using the method in the video I haven't had issues with multi-couplers either. Mind you, I generally just use a two-quad coupler setup to make a single more structurally rigid joint. I've never tried to dock, say, two separate ships onto a single bi-coupler. Perhaps some screens of the design you're referring to might help.

[OUScooby]

Perhaps I'm misunderstanding something here. Are you referring to having problems with multiple ports on the bi/tri/quad-couplers or the six port cube? Either way I've never experienced the lack of cross-feeding with the six-port, and since I started using the method in the video I haven't had issues with multi-couplers either. Mind you, I generally just use a two-quad coupler setup to make a single more structurally rigid joint. I've never tried to dock, say, two separate ships onto a single bi-coupler. Perhaps some screens of the design you're referring to might help.

In my particular example I wasn't using the tri or bi couplers or the cube. I had three radial mounted fuel tanks around the center of a ship, each with large docking ports on them. Four sections were docked in orbit, not connected via docking ports when building in the VAB. When I docked the last section with the three clusters of engines I discovered only one cluster of engines was drawing from the tank above them. The other sections had their ports docked securely but weren't cross feeding. The solution to this would be to send fuel lines in both directions between all tanks, that way which ever port is cross feeding it still draws from all tanks. Here is some pic to better explain the design.

It docked together in that order, first the command pod section with docking ports on the bottom of each radial tank, then two center sections with docking ports and both ends of the radial tanks, then the engine section with 5 LV-N engines drawing from each radial tank (for a total of 15 engines).

Here are

[Benie]

if you aren't careful with how big your station is and how efficiently you use parts you will run into some performance issues.

Aye. My simple Space Station causes my computer to lag when my ship is attempting to dock with it. I know why; too much lighting. But I don't feel like re-launching it (I really need to redesign it anyway so getting to the Docking Ports are easier, without risk of hitting the Solar Panels. And I seriously wish there was a way to test the lights before I get it up there.

[Coneshot]

This was multi-docked, I had to give it a love tap to make the last 3 connect.. hard to see but it's 5 at once:

[DMagic]

I think there are a few issue with multiple docking ports and fuel flow. One, is that some kind of fuel loop can be created. Another is that fuel might only be able to flow through whichever is considered the "primary" docking port. There is a post in this thread about some of the issues with fuel flow and multiple ports:

http://forum.kerbalspaceprogram.com/showthread.php/26660-Interplanetary-ship-design-problems?p=329049&viewfull=1#post329049

Most of these examples are using tri-couplers, but I think something similar is happening with any multiport situation.

[Tiron]

In my particular example I wasn't using the tri or bi couplers or the cube. I had three radial mounted fuel tanks around the center of a ship, each with large docking ports on them. Four sections were docked in orbit, not connected via docking ports when building in the VAB. When I docked the last section with the three clusters of engines I discovered only one cluster of engines was drawing from the tank above them. The other sections had their ports docked securely but weren't cross feeding. The solution to this would be to send fuel lines in both directions between all tanks, that way which ever port is cross feeding it still draws from all tanks. Here is some pic to better explain the design.

*Photo Snip x4*

It docked together in that order, first the command pod section with docking ports on the bottom of each radial tank, then two center sections with docking ports and both ends of the radial tanks, then the engine section with 5 LV-N engines drawing from each radial tank (for a total of 15 engines).

Yeah. The problem here is the way multi-docking works: the first port to lock on forms a full connection capable of crossfeeding fuel. But the stucture's always built as a tree, logically, so the 2nd and 3rd ports can't also fully connect. They merely form physical connections, as if there were a strut connecting them.

Simply put, that design is never going to work as it's currently built, because you can't have fuel crossflow through all three outer arms at once. You're either going to have manually shift fuel around or redesign it so that all the fuel flow goes goes through a single, defined port between sections.

Sucks but it's a fundamental limitation of the game design atm.

Edit: Or rebuild it so that the three outer arms on each section are three seperate pieces. The easiest way to do this would be to connect them to the center section via a docking port pair. After you make the initial dock, you could then go around and undock the ports connecting two of the outer arms to the center (ONE can stay connected, because it functions as the parent for the central section), then reload the scene. Disconnecting the ports connecting them to the center will allow their top port to change into 'full dock' mode, and reloading the scene will cause the ports connecting them to the center to reconnect in 'physical connection' mode and hold the thing together. Do it right and nothing moves physically, but logically the tree changes so that each outer arm is a separate 'branch', with fully connected ports all the way down.

Edited July 4, 2013 by Tiron

[espm400]

In my particular example I wasn't using the tri or bi couplers or the cube. I had three radial mounted fuel tanks around the center of a ship, each with large docking ports on them. Four sections were docked in orbit, not connected via docking ports when building in the VAB. When I docked the last section with the three clusters of engines I discovered only one cluster of engines was drawing from the tank above them. The other sections had their ports docked securely but weren't cross feeding. The solution to this would be to send fuel lines in both directions between all tanks, that way which ever port is cross feeding it still draws from all tanks. Here is some pic to better explain the design.

-snip-

It docked together in that order, first the command pod section with docking ports on the bottom of each radial tank, then two center sections with docking ports and both ends of the radial tanks, then the engine section with 5 LV-N engines drawing from each radial tank (for a total of 15 engines).

Here are

Thanks for clarifying that, I don't like when I misinterpret stuff like that as it make me feel somewhat foolish. Anyways, I haven't built many ships with multiple ports set up in this manner, and the few I made were either abandoned or had cross-feeding to the central tanks as well as a port in the center. Now I may not have a full grasp on the way the parent-child handles stuff like that, so I will defer to those with said knowledge (as I said, I mainly just use a single multi-coupler with ports to strengthen and line up my parts). Just a quick thought - similar to Tiron's - before I go; would you be able to build the majority of the ship in 3x symmetry (for ease and accuracy) and just switch the 1x for the docking ports themselves? I just know from when I was learning how to build asparagus-style rockets how annoying it is to do manual symmetry, as I originally did 2x three or four times on the core for ease of staging, before I realized it was actually easier and quicker to adjust the staging than to manually line parts up perfectly, unless I'm missing something (which is often the case).

[NoMrBond]

You can manage the unfortunate fuel balancing issues stemming from the single-parent craft with multiple docking point problem with either

TAC Fuel Balancer or RogueTech Fuel Ducts

[OUScooby]

Just a quick thought - similar to Tiron's - before I go; would you be able to build the majority of the ship in 3x symmetry (for ease and accuracy) and just switch the 1x for the docking ports themselves? I just know from when I was learning how to build asparagus-style rockets how annoying it is to do manual symmetry, as I originally did 2x three or four times on the core for ease of staging, before I realized it was actually easier and quicker to adjust the staging than to manually line parts up perfectly, unless I'm missing something (which is often the case).

I don't know. Perhaps that may work if I was building the whole thing as one ship in the VAB, but I was building each section and docking them in orbit. I never had any structural issues with the ship, even though two of the docking ports weren't cross feeding fuel they were still holding together strong, and the cross feed issue can be easily worked around by adding fuel line in both directions between all the tanks.

I'm curious about one thing, in your video you had a tri coupler with three docking ports docked to three FL-T800 fuel tanks which were then docked to another tri coupler below it. In your video your were only testing these docks on the launch pad, but did you ever incorporate that design into a rocket, and did you notice if you were feeding from all three of those tanks?

[espm400]

I don't know. Perhaps that may work if I was building the whole thing as one ship in the VAB, but I was building each section and docking them in orbit. I never had any structural issues with the ship, even though two of the docking ports weren't cross feeding fuel they were still holding together strong, and the cross feed issue can be easily worked around by adding fuel line in both directions between all the tanks.

I'm curious about one thing, in your video you had a tri coupler with three docking ports docked to three FL-T800 fuel tanks which were then docked to another tri coupler below it. In your video your were only testing these docks on the launch pad, but did you ever incorporate that design into a rocket, and did you notice if you were feeding from all three of those tanks?

First off, let me state for the record, that isn't MY video, just one that helped me out in a big way. When I started incorporating multi-couplers into my designs anywhere but at one of the ends, all but one would fall away when I decoupled, and until I saw that video I was lost as to why. Secondly, I use that setup (given, with a quad-coupler) in virtually all of my interplanetary and station designs, mainly for the added rigidity. That being said, all four ports would be docked (I could right click and undock them), however in such a case, I couldn't tell you (without some testing) if all of them were cross-feeding, as they were all connected. On the testing side, I spent some time tonight making a design vaguely similar to yours and assembling it in orbit. From what I gathered, it was basically a center stack feeding the outer stacks with engine blocks at the rear.

That was using 3x symmetry for everything (I had just never experienced this). First off, docking was an absolute bitch, and this is coming from someone who has all but mastered docking perfectly with my own designs. Just to let you know, I've always been a fan of having a central core plus engine block with exterior tanks feeding the central core. That way if I have unexpected fuel or engine issues, you don't end up with a completely uncontrollable craft (most of the time). As I haven't yet tried out my own suggestion to you, and won't get around to it tonight (it's 6:30am and I'm tired. Thank god I'm off work today), I will try it out at some point tomorrow. I also have a suggestion for your future craft building; stick with a central main core c/w engine block and cross-feed your externals (with or without engines) into that. That way you not only eliminate the fuel tree issue, but it's a damn sight easier to ditch your dead weight (well, mass technically).

P.S. I've never understood why people use 3x or 6x symmetry. For me, I require 4x RCS thrusters whenever I place them, and using either that with 3x symmetry everywhere else, or 3x thruster blocks leads to an aerodynamically, aesthetically, and/or unbalanced ship. Maybe I'm missing something (again, I'll never say I'm infallible), but for me, 99% of the time it's 2x, 4x, and in the case of asparagus staging (rare for me nowadays. They're ugly ships and I also now use FAR), 8x.

[iDan122]

The max I did was connect 3 to 3. It was quite easily, they just automatically magnetically correct themselves.

[Spock_Kerbin]

the following ship is made of multiple docks in multiple configurations, it was built in VAB and has ahd most of the parts successfully delivered to orbit and then docked (4 XL docks hitting simultaneously)

the prob I had that this ship overcomes is that the MULTIPOINT blocks are TOO DAMN HEAVY !

and also, they do no accept Symmetry placed dock ports around an axis, so you can't use it asa core and add four objects around it

[Spock_Kerbin]

this was the previous design,

as mentioned, to heavy to get to orbit AND it falls apart in various stages as they are not connected

[Starwaster]

One thing I have noticed is that multiple pieces docked together decreases performance in a non-linear fashion. The more docking connections you have, the worse it gets when you add a new one.

I had assembled a ~200 part space station in orbit made up of 27 sections docked together, most of which were double orange fuel tanks that couldn't all be reasonably launched at once. The framerate was choppy even in time warp, and approaching it with a ship rendered things almost unplayable.

I decided to do a minor cheat and replaced the station in orbit with the exact same one, except as a single "ship" with all the connecting docking ports removed. After that it was smooth as silk.

Apologies for the necroposting but I just had an idea.... if multiple docking ports cause lag then it has to be because of the module code in the part. How about a docking port that stops being a docking port after it's docked? It would require a custom plugin and a custom part. (the part code would be identical except for the addition of a parameter in the MODULE code for the port which signifies that this is going to be fused later)

The way it would work is that in the VAB, nothing happens, the part is treated normally and ignored by the plugin. When an actual craft is spawned that has two of these ports connected OR if a craft is docked and results in two of these ports connecting, the MODULE{} code that identifies the part as a docking port is removed. The two parts would just like any other static part.

The only real downside I can see is that 'you better mean it' if you use these because they're probably not coming apart again. (technically I suppose it's possible, it's trivial enough to identify that these two parts WERE docking ports using their names but then a mechanism needs to be put in place to not only identify the parts, determine that you want to separate them, reinsert the docking port module code and then separate the craft, all of which adds complexity that might not be wanted)

[PTNLemay]

Something disturbing just happened. I actually successfully docked 2 space station components together... WITH multi-docks! I'm not sure, but I think that's a sign of the approching apocalypse, like pigs flying and fire raining. It's UN-NATURAL and unholy!

http://i.imgur.com/UEofJM3.jpg

http://i.imgur.com/J0oywjI.jpg

All silliness aside, thank you to whoever it was who gave me the triple-mini-docks idea. Worked like a charm, and it feels solid like a rock.

Edited August 15, 2013 by PTNLemay