Don't do this, it will annoy you!

[katateochi]

I thought I'd had a good idea, turned out to be the most infuriating thing ever!

I've been building a mission to go and clear up the remaining science on Mun. I have a manned lander which will make several trips to the surface, landing in different biomes. In some biomes I just need the gravity and surface EVA data, in others I need the full set of sensors, so I have a couple different sci modules so the lander just takes the sensors it needs for each biome.

I'm also not transmitting in this mission so the modules will be brought back up and redocked with the orbital craft and then a fresh module will be taken down to the next biome.

But one of the simple modules has caused me serious frustration.

This little guy, which I was calling a "science disk", is very flawed. I thought it would be neat to have these little disks, with different sensors (this is just a purely gravity one) and depending on what you needed to do you'd pick up the required one before descending. However these little blighters have been seriously annoying.

I also have larger modules that have the materials and goo containers and those worked perfectly.

The problem is that the configuration of this small module causes a bug in the docking ports. I could pick one up and use it, but when bringing it back it just simply refused to redock to the orbital craft. I wasted several hours trying to figure out what was wrong and eventually I found this bug report, so I checked my Pfile and lo; one of the ports did indeed have the wrong state. So I changed the state and reloaded and it docked. I thought it was just a 1 off glitch and carried on.

But it happened again and again (with all the small modules with the above design), and on the 2nd (3rd, 4th, 5th, arrrgh) time changing the state in the Pfile didn't solve it. If I perfectly lined up to dock and then undocked the module from the lander and let it float on towards the orbital craft it would dock when it arrived. I thought I'd found a work around, but infact that just created other problems because the port still had not been set to the right state and in some cases it was actually just being held in place by the other ports magnetism, the port that should have docked was not actually doing anything. If that happened and I did a reload or approached the orbital craft the module would just float off and neither port would then respond so I couldn't recover it.

And sometimes I couldn't do that because it wouldn't undock from the lander, the connected port would "undock" but then it would instantly be attracted to the lander again because the other ports magnetism engaged and just held it there.

The lander on its own didn't have any problems docking to anything else, I could dock directly to the orbital craft or pick up the other larger modules, but with that small module this bug was almost guaranteed to happen.

I've never had anything like this happen before, even with some really odd designs.

I think there where several things going wrong, and all because the two ports on the module are so close together, only separated by a small battery.

1) they interfered with each other resulting in their states not getting reset correctly when one was undocked. (maybe even they where trying to dock with each other)

2) being so close meant that when one was undocked the other was close enough to whatever it had just undocked from so it would start trying to dock and its magnets would just hold it there.

I've changed the design and put a probe core in-between the battery and one of the docking ports and so far that design has worked. Just thought I'd share this so you don't waste time on designs like this!

The moral of the story is; don't have two docking ports that are back to back with very little space between them!!

[boomerdog2000]

I'm not sure if that's the issue. I believe it lies with the game not liking to undock pieces that would count as debris, so they need to have a core of some sort.

[katateochi]

I'm not sure if that's the issue. I believe it lies with the game not liking to undock pieces that would count as debris, so they need to have a core of some sort.

It could be, but I'm not convinced because the other larger modules which work fine also don't have a core so they're also basically debris. I've never had problem docking/undocking with 'debris' before.

[sanoj688]

Did you try sticking a mechjeb part on all of your science pods?

[Wallace]

I've had the docking bug occur on a bundle of batteries with a mechjeb box on the side, so that doesn't seem to prevent it. It doesn't always happen to things without a pod, but podlessness does seem to be the root of the issue.

[numerobis]

Mech job was a pod for a while, but no longer is, so it won't help.

[KerbMav]

I think there where several things going wrong, and all because the two ports on the module are so close together, only separated by a small battery.

1) they interfered with each other resulting in their states not getting reset correctly when one was undocked. (maybe even they where trying to dock with each other)

2) being so close meant that when one was undocked the other was close enough to whatever it had just undocked from so it would start trying to dock and its magnets would just hold it there.

I've changed the design and put a probe core in-between the battery and one of the docking ports and so far that design has worked. Just thought I'd share this so you don't waste time on designs like this!

The moral of the story is; don't have two docking ports that are back to back with very little space between them!!

You know what? I think that is exactly what is happening.

Maybe this is even a clue to mysterious undocking bug.

[magnemoe]

My Jool mission used an larger version of this, take an material lab, put an goo container on one side, battery on the other side, add the other science stuff, probe core and two junior docking ports.

The Tylo and Laythe lander had a seat on top of the docking port and used a disposable lander, Kerbal leave seat and seat is jettisoned before docking. Vall, Bop and Pol used a reusable one who just swapped science module.

Had one issue with docking port bug, where the lander did not want to undock from the science module.

Undock science module from mothership, undock lander, dock science module to mothership again and dock lander to next science module.

[Deadweasel]

I had the same problem. Trying to dock this

To this

And carry it to be mounted to this (atop the drive ring)

First bug was encountered with the rover using Quantum Struts. As soon as the dropship docked, all control went out the airlock, and it just kind of hung there frozen until I switched to the Spaceport and back. After that, I got the whole shebang docked to the transport, but the whole assembly started bucking to and fro wildly. Switch to Spaceport and back, and all is calm once more, but from there I ran headlong into that dock state bug for the first time. I was really confused about why the dropship wouldn't undock at all, until I found a detailed post describing the situation. I got pretty confused trying to identify exactly what had happened from that post, so I tried dropping out of the game and re-loading. That ended up fixing the issue that one time, but from there it was really obvious those Jr clamps are pretty crap. They shuffle and pull away far too easily, or just bug out.

That same dropship design has performed many successful drops of a larger rover using Quantum Struts, so I'm relatively certain the bugs I encountered are related to that one stupid port, which I've never used until I tried to deploy such a tiny rover in that way. The main differences with this rover are that it uses the RollKage mod for the cabin, on the top of which sits that little Jr clamp, and has a regular docking clamp on a decoupler on the bottom. The "Kurb Burner" does include a probe core for automated movement, so there shouldn't be a problem with detection as debris (it shows as a probe when cut loose from its launcher or the dropship).

I'll know more about potential causes tomorrow evening, after I've re-tooled and re-launched the entire fleet. Again. (The drive ring, cargo carrier, dropship and rovers are all launched independently because of the ridiculous tonnage and part counts the fully assembled mission represents) *sigh*

[Kasuha]

Is that just two docking ports with some gravimeters attached or is there something in between? I'ts hard to tell.

I'd probably put some Modular Girders in between them.

I have similar experience, too - I am not using such small modules, my "lifeless" modules are orange tanks with a docking port Sr. on each end and occasionally they refuse to undock on one end. So far I always managed to work around this issue without having to change my files, though.

Edited November 8, 2013 by Kasuha

[Deadweasel]

Is that just two docking ports with some gravimeters attached or is there something in between? I'ts hard to tell.

I'd probably put some Modular Girders in between them.

I have similar experience, too - I am not using such small modules, my "lifeless" modules are orange tanks with a docking port Sr. on each end and occasionally they refuse to undock on one end. So far I always managed to work around this issue without having to change my files, though.

Haven't seen it at all or ever until my first attempt at making an ultra-compact rover that seemed to be a perfect fit for the Jr port, but between it just happening to occur with my first use of that port, and watching that port rubber band all over the place once the docking was completed, I'm just abandoning that thing and going with a disposable standard port for carrying instead. (Not like I'm ever going to be able to pick it back up anyway, I can't still-hover worth a darn yet)

[Kialar]

Adding a small probe core to every dockable artifact fixes that.

[KerbMav]

Note to self: Finally get to edit the KER motherboard parts to be torque less RFID chip "command" modules ...

[Corw]

Does seat count as command module? It is in that tab, but does it count?

[KerbMav]

I am not at home, open the part.cfg and have a look!

But it should, or else a rover without pod and/or probe core would do nothing (apart from rolling down the hill maybe).

[FITorion]

I've never encountered this bug. It is concerning though as I've made this...

My "Science Package" ... 2 ports, mat lab, 2 goo, 3 temp, 3 seismic detectors, 4 Gravioli detectors, and 2 solar panels. I've never had it fail to undock... I've also never left it unattached to something else with a command pod of some type. But this is supposed to allow me to use the same lander repeatedly and just swap the Science Package each time.

It would be very bad if at some point I was unable to undock the Science Package from the lander upon its return to the command ship or unable to dock with the commend ship.

[BostLabs]

I had the same problem. Trying to dock this

<snip>

I don't think I can help with the issue, but I wanted to say those are beautiful crafts.

[katateochi]

Did you try sticking a mechjeb part on all of your science pods?

I'm currently playing 100% stock (which is unusual for me!) so don't even have MJ installed.

Is that just two docking ports with some gravimeters attached or is there something in between? I'ts hard to tell.

I'd probably put some Modular Girders in between them.

I have similar experience, too - I am not using such small modules, my "lifeless" modules are orange tanks with a docking port Sr. on each end and occasionally they refuse to undock on one end. So far I always managed to work around this issue without having to change my files, though.

So you get the problem with a very large "lifeless" (good term btw) module, hmmm. In this case it might be something else specific to the Sr docking port. I've heard others having issues with the Sr that didn't occur when using the standard.

I did put a modular girder after I got this problem, but then I decided that I didn't like the look of it now and went for the probe core as it was more compact. I could have used the hex-strut part but I'm frightened of them (they've caused me much weirdness in the past).

I've never encountered this bug. It is concerning though as I've made this...

snip

That's very similar to the larger module that I had and I've not had any problems with the larger module, just the small one that caused by grief. Neither module has a core which is why I suspected size to be the culprit. But others have said they've had it with larger things so....it's still a mystery, so many variables so its hard to really lock it down, and I've not had time to be properly scientific about it (I'm outsourcing that to you guys!).

I had the same problem. Trying to dock this

*snip*

You might be having issues from the Q-struts? They can do some really weird things and produce phantom forces that result in madly spinning ships and break-dancing rovers (and other even stranger things).

I've never (until now) had issues with the Jr ports and I use them quite a lot, but generally for quite small things.

Awesome craft btw.

Does seat count as command module? It is in that tab, but does it count?

not sure, I think it has to be occupied before it is an active core.

So this is a curious one, from what we've found so far;

1 - it can happen when docking to small modules without a core (Jr port)

2 - it can happen when docking to larger modules that have a core (Jr port)

3 - it can happen when docking to large modules without a core (Sr port)

4 - it hasn't happened when docking to larger modules without a core (Jr ports) - conflicting result with No3

Has anyone had this problem with a standard port?

From this we can't really say that not having a core is the cause and we can't say that size is the cause either. hmmmm. its could be something else entirely!

more observations needed!

[Deadweasel]

Heh, thanks, the fleet is my pride and joy (at the moment).

Yeah there used to be an issue with that, but from what I understand, that largely has to do with the struts being active when a craft loads, while not being specifically attached to something nearby. The one attempt I was able to make on that docking so far was done while the struts were accidentally left active on the rover before the connection. It may come down to just making sure I have them switched off before completing the rendezvous. I can semi-confirm this is likely the problem with the locking problem, as Venture's vehicle bay is strewn with those quantum struts, and they cause no issues during launch or flight, especially since even when the bay doors are open, those struts are still attached to the open doors. I just have to make sure I shut them down before docking or launching the dropship, or things get... weird.

As for the port bug, there is something to consider regarding the ports involved. Jr and Sr are both relative newcomers to the collection (compared to the standard port), are they not? Is there something about their models that causes some kind of limit violation within the game's engine, resulting in the screwy state corruption in the persistence file?

What about the shielded docking port? Anybody run into this bug using that one?

Comparing their .cfg files, there really isn't any difference where the involved modules are concerned, and the rest are just simple placement and tolerance specs. Nothing really stands out that could point to a potential cause there. It has to be something related to their interaction with other parts. I'm betting the initial call-out regarding back to back ports is a major player in this case, but then, that means there's ALSO something else at play here, given the issues I experienced with my particular setup.

Either way, with what we've seen collectively so far, it looks like the standard port seems to be exempt from this bug.

Looking forward to the new attempt tonight.

[Deadweasel]

Looks like the issues are wiped out on my side.

The rover was given a regular docking port to replace the Jr one, and the quantum struts were removed from it altogether.

Delivery and retrieval was uneventful, with the dropship maintaining complete control authority after locking down on the rover.

Stowing the rover to the main ship similarly went without a hitch, with the dropship de-coupling easily and without bugs.

So far, everything looks good. However, Venture itself still uses quantum struts to keep the massive vessel stable, so time will tell if those impart any weirdness on the rover when the time comes to deliver it to the landing site.

[katateochi]

@Deadweasel - That's interesting, so removal of QStruts and replacement of the Jr port with a standard resolved it. So it's one of those two (my suspicions are that it's the Jr port). Is there any chance you could do a test run and put the Jr ports back but leave the Qstruts off and see of the problem returns?