Issues with Docking Ports - Again...

[capi3101]

Howdy, y'all.

I've recently built a circular space station, a nice hub and wheel design using a set of instructions posted originally by Tex_NL. I call my space station "Mere" (which is a stupid name; I'm thinking about changing it but that's all that important right now). Here's how she looks:

I made the decision early on in the design to go ahead and add "locks" in between the modules of the ring to go ahead and link them together, so that I would actually have a fully constructed ring (the original design plans don't call for the locks). Over the weekend, I added the fourth and final lock to the design and I've noticed something off about the station - while I did get a good double-dock on the locks when they went in place, all four of them now exhibit a visible "gap" between some of the ports. The game insists the ports are still docked, though. Here's what I mean:

(That particular set of ports is exhibiting the smallest gap I'm seeing; truth be told that probably wasn't the best screenie I could've picked).

Any ideas what might be causing this? More to the point, I have plans to move my station to Minmus once I'm done grinding science out of the Mun, so is this something I need to worry myself about? Any suggestions on how to go about fixing it?

Copy of my current game's persistence file, in case anybody needs that data to solve the issue.

Thanks in advance, y'all.

[cantab]

I wonder if you haven't got a little bit of internal strain, showing itself as the gaps between the docking ports. The precision needed in the position of the docking ports to get perfection is probably beyond what can be done in the VAB.

You'll just have to see if it flies stably.

[capi3101]

I had thought that the difference might be due to minute differences in the rotation of the constituent parts. I don't know the best way to figure out if that's the case or not; one of the reasons why I linked the persistence file.

[Frannington]

I'm only guessing, but it looks like the diameter of the station is too small. The ports are locking, but the physical shape dictates that they don't meet head-on.

This is going to be a stupid question but... did you assemble that in the VAB and actually launch it, assemble it in the VAB and Hyperedit it into orbit, or did you assemble it on-orbit with multiple launches?

Apologies if this is a question I'm not supposed to ask because it's impolite. I'm still trying to find my way, and often see constructions here that seem like they're impossible (or would need infinite patience).

[-Velocity-]

I'm only guessing, but it looks like the diameter of the station is too small. The ports are locking, but the physical shape dictates that they don't meet head-on.

This is going to be a stupid question but... did you assemble that in the VAB and actually launch it, assemble it in the VAB and Hyperedit it into orbit, or did you assemble it on-orbit with multiple launches?

Apologies if this is a question I'm not supposed to ask because it's impolite. I'm still trying to find my way, and often see constructions here that seem like they're impossible (or would need infinite patience).

As far as I know, it's only possible to assemble a genuine ring (a loop of parts) in orbit using docking, because otherwise the game's part-tree system prohibits you from building a part "loop".

If I had to guess, there are gaps in the structure because the parts are close, but not quite, the perfect size. So the station almost fits together perfectly, but not quite.

Anyway, it's a pretty impressive structure. I had a gigantic spaceship (like 1700 tons) I launched in two pieces once, and the two pieces were joined by four simultaneous Clampatron Sr. docking ports. It was really tough to get all four of the docking ports to attach at the same time. But... that wasn't a RING. I'm really impressed that this ring station turned out as well as it did.

[Sirrobert]

I'm only guessing, but it looks like the diameter of the station is too small. The ports are locking, but the physical shape dictates that they don't meet head-on.

This is going to be a stupid question but... did you assemble that in the VAB and actually launch it, assemble it in the VAB and Hyperedit it into orbit, or did you assemble it on-orbit with multiple launches?

Apologies if this is a question I'm not supposed to ask because it's impolite. I'm still trying to find my way, and often see constructions here that seem like they're impossible (or would need infinite patience).

It's a fine question, don't worry

I'm pritty sure he assambled the ring in orbit. Because of the tree structure KSP uses to build crafts, it's impossible to make such a ring in the VAB.

As for the question: If the game claims they are docked, I'd guess that means they are still linked, and thus you can fly it around.

Offcourse, quicksave before you go crazy

[-Velocity-]

More to the point, I have plans to move my station to Minmus once I'm done grinding science out of the Mun, so is this something I need to worry myself about?

1) Alt-F5, save as "Pre station move test";

2) Try moving the station to Minimus;

3) Observe;

4) Alt-F9, select and load "Pre station move test".

[Franklin]

It's a common issue, turns out. Docking ports have a lot of flexibility, but still cling impressively, which gives you what you're seeing there. Gaps or otherwise mis-alignment despite the ports being docked tight.

I made a similar thread a week back: http://forum.kerbalspaceprogram.com/threads/94605-Editing-Docking-Port-Connections-In-Save-File

Which more or less sums up to it being possible to edit your save file to correct these gaps, but the effort might outweigh the value. My current ring has a mis-aligned port that's otherwise docked tight that I've just come to live with.

[capi3101]

This is going to be a stupid question but... did you assemble that in the VAB and actually launch it, assemble it in the VAB and Hyperedit it into orbit, or did you assemble it on-orbit with multiple launches?

I assembled the station in Munar orbit with multiple launches. Nineteen to be exact - the hub, four missions for the spokes, eight missions for the individual ring modules, and six missions for the locks (I had issues with two of the locks - one was the original design, one was a corrective attempt that turned out to be too big to connect the two ports together - the ports were clipping into one another; try as they might they wouldn't come together to dock)). I started out by putting the thing together in the VAB as per Tex_NL's original instructions, adding a lock to one side to see how well it would fit and then adjusting the length of the spoke girders until it looked right.

1) Alt-F5, save as "Pre station move test";

2) Try moving the station to Minimus;

3) Observe;

4) Alt-F9, select and load "Pre station move test".

That'll probably be what I wind up doing. I'll have to let y'all know how well it winds up working.

It's a common issue, turns out. Docking ports have a lot of flexibility, but still cling impressively, which gives you what you're seeing there. Gaps or otherwise mis-alignment despite the ports being docked tight.

I made a similar thread a week back: http://forum.kerbalspaceprogram.com/threads/94605-Editing-Docking-Port-Connections-In-Save-File

Which more or less sums up to it being possible to edit your save file to correct these gaps, but the effort might outweigh the value. My current ring has a mis-aligned port that's otherwise docked tight that I've just come to live with.

Yeah, I saw that thread last week, and I mentioned having "a similar issue" then...hence this thread and my promise to stop hijacking that one. Your ring turned out pretty freakin' awesome, BTW.

[tsotha]

If you can't find a solution you can always call it "Merde" instead.

[Friend Bear]

Looking at your problem briefly, it seems familiar. When this kind of thing happened to me, sometimes backing out and reattaching fixed it, but it might not.

I would suggest downloading Kerbal Attachment System and using the struts. This allows you to install struts after construction with a kerbal but dragging the strut into place and connecting the two points. If there is a disconnect, two or three struts should prevent all motion on the joint.

[Claw]

Multi-docked ports are connected a little differently in the tree structure. I'm not certain, but I think these multi-ported connections are sort of "recalculated" at times. So while a single docking port has the integrity of any other connected part, multi-docking ports react a bit differently. So what you are probably seeing is the results of the "recalculations" where the port knows it's connected and stops moving when the whole structure is reloaded. I would guess that at times the gaps may even appear different, but I haven't done much of this sort of multidocking myself.

And I agree, your ring station looks great. Nice job Capi.

Cheers,

~Claw

[tg626]

If you do preassemble in the vab, be sure to take it to the pad to inspect it. Otherwise you may get unexpected results when physics are applied.

[capi3101]

I would suggest downloading Kerbal Attachment System and using the struts. This allows you to install struts after construction with a kerbal but dragging the strut into place and connecting the two points. If there is a disconnect, two or three struts should prevent all motion on the joint.

I have to haul the strut up there with a container or grab it off another craft, right? I use KAS (those are KAS winches on the insides of the locks and I did a big spacewalk to add a series of radial connector ports to the hub), so this is an option for me. Still haven't used it all that much.

Occurs to me that I added those winches and ports to assist with the docking procedure but I wound up not needing them...anybody foresee disaster if I try to hook 'em up and try to use them to reduce the gaps?

Glad y'all like the design; Tex_NL really deserves the credit for it. I just followed a recipe.

[Friend Bear]

I have to haul the strut up there with a container or grab it off another craft, right? I use KAS (those are KAS winches on the insides of the locks and I did a big spacewalk to add a series of radial connector ports to the hub), so this is an option for me. Still haven't used it all that much.

Occurs to me that I added those winches and ports to assist with the docking procedure but I wound up not needing them...anybody foresee disaster if I try to hook 'em up and try to use them to reduce the gaps?

Glad y'all like the design; Tex_NL really deserves the credit for it. I just followed a recipe.

Yeah you have to haul it up there. That's why I attach a couple of containers with the generals to orbiters. You can also attach the item you want to use to the ship instead of putting it in a box and it can just be removed/replaced.

I figure the cost is so low its not entirely unfounded.

Might be worth it since you want fuel for the journey anyways? I don't know.

Edited October 1, 2014 by Friend Bear

[capi3101]

I was fixing to send up an unmanned lander anyway; I could easily throw on a couple of parts containers, detatch them from the lander and re-deploy them to the station. Any suggestions for which parts (in your experience) would be the most useful to put in them? A couple of struts, obviously. Maybe some radial chutes.

[Friend Bear]

Yeah I do that for my landers too. The only down side in this situation is there are no mounts for you to transfer full containers to the station, but its really not that big of a down side.

[capi3101]

You can grab the mounts...I know because I was able to do it with my last spacewalk mission. I'd just send up an empty mount of two along with the same flight, use a Kerbal to attach the mounts and then start moving the containers on over. KAS won't let you grab the mount while there's a container in it, unfortunately, which is too bad because it would save both time and mass. On the other hand, extended spacewalks are kinda fun...

[Friend Bear]

Oh! That is way good to know.