Game-induced physics warp?

[strider3]

What are some of the causes? I am having problems with a station I'm putting together in orbit...a second or two after docking the next part, I'd get a wiggle and other parts of the station would come off. DStaal pointed out that the upper left time indicator was yellow, indicating a slow down. My previous station was much larger with many more parts than the one I'm currently putting together and it never suffered from this issue and the time indicator was always green. So if not craft "complexity", what else might I look at as a cause?

 

Edited January 10, 2020 by strider3

[HvP]

If you're getting sudden jumpiness from your station after docking or switching to the station after loading then the problem is often due to autostruts. The biggest offender seems to be autostrut to heaviest part, and occasionally with autostrut to root part.

The reason it happens is because the autostruts realign themselves after a staging change, including docking, and since this often includes having a new or different heaviest/root part then the autostruts let go of what they were holding and jump to a different part that could be across a particularly flexible joint. This can cause weird forces across the station and sometimes ends up being a buggy mess.

The best advice so far is to use autostruts sparingly and to try strutting to grandparent part if you really need them.

Edited January 10, 2020 by HvP

[Superfluous J]

docking ports are huge offenders when it comes to part count. An open docking port is constantly checking if there are any nearby ports to connect to. If your station has a lot of docking ports then that could be causing the yellow timer.

[strider3]

23 hours ago, HvP said:

If you're getting sudden jumpiness from your station after docking or switching to the station after loading then the problem is often due to autostruts. The biggest offender seems to be autostrut to heaviest part, and occasionally with autostrut to root part.

The reason it happens is because the autostruts realign themselves after a staging change, including docking, and since this often includes having a new or different heaviest/root part then the autostruts let go of what they were holding and jump to a different part that could be across a particularly flexible joint. This can cause weird forces across the station and sometimes ends up being a buggy mess.

The best advice so far is to use autostruts sparingly and to try strutting to grandparent part if you really need them.

HMmm...I was under the impression that once you set the "Root" part in the VAB, it stays set? But, then again, when I bring the four station arms up to orbit, to attach them to the central hub, those crafts will also, by necessity, have a root part as they are separately constructed in the VAB. I never use "heaviest" part for a refueling station (or much else, for that matter) as that will change as I transfer fuel. Is there some way to stop this transfer of "Root" part?

 

23 hours ago, 5thHorseman said:

docking ports are huge offenders when it comes to part count. An open docking port is constantly checking if there are any nearby ports to connect to. If your station has a lot of docking ports then that could be causing the yellow timer.

I'm guessing there is no way to turn off this docking port behavior, temporarily, until I'm ready to actually dock something? In truth, even if I could, if you can't turn it back on for only the one port you currently want to dock with, the results would be the same.

Here's a screenshot of the "problem child" right after some parts come off, about a second after "welding" the last arm (this attempt made it past the docking stage but came apart during the weld), and also a screenshot of a previous version which did not have so many issues during docking and welding (obviously). The octo-girder, that the 4 arms attach to, was set as root in the VAB. As I said though, each of the individual arms launch as a separate craft, with it's own root. As mentioned, lots of empty docking ports (more and more as each arm is attached!). These are Konstruction weldable ports but I don't think it matters according to 5thHoreseman's statement (I did start this search for answers at the "Konstruction!" mod forum, but the more replies I got, the more it seems to be more than just a single cause). Each arm's "inner" octo-girder section (the one with the port on it) is set to auto-strut to root part, the other parts, including the other (outer) octo-girder, are all set to grandparent as is everything else on the central stack other than the previously mentioned "root" part. You'll also notice a smaller amount of lights on the previous version...the increased lighting on the new version is, I'm guessing another additive to the slow down? You'll notice how many tanks I had managed to attach on the previous version, possibly covering up "empty" ports and reducing the slowdown with each additional tank. I started over as the portable strutting on the old version was getting out of control and trying to attach a portable strut during EVA also resulted in parts coming off, at time, but not always. And besides...it was getting ugly as sin 

 

 

So, friends...any suggestions going forward? I've been using struts, of one type or the other to 1. keep these parts together during launch, which is a primary concern. Without struts, the various parts wobble like an earthworm during launch and orbit insertion...and sometimes with spectacularly disastrous result...very "kerbal like". 2. To try and fend off the Kraken once the station is built and very large ships dock for refueling. I'm open to trying anything, at this point. I've been trying to get my station "commissioned" for over a month and exasperation is setting in.

And while I'm asking, would the "slow down" be helped with a higher performance computer, or is it a product of the game, no matter what? I ask because MS is getting back into the flight simulator game in 2020 and I would hazard a guess that my 6 year old box won't run it.

Edited January 11, 2020 by strider3

[AHHans]

6 hours ago, strider3 said:

HMmm...I was under the impression that once you set the "Root" part in the VAB, it stays set?

Not really. As you already remarked, when you dock (or attach something with a claw) you are combining two vessels into one. And this will be indeed one combined vessel, with only one root. This new root will be the original root part of one of the two docked vessels, but I don't know how exactly this is chosen. It could be the root part of the older (launched earlier) vessel, or of the one that you were (not?) controlling when the docking happened, or something else.

6 hours ago, strider3 said:

Is there some way to stop this transfer of "Root" part?

No. (Well, "not dock"...) I believe that the "one root part per one vessel" and "docked vessels become one vessel" mechanic is seriously deep in the guts of the KSP code.

6 hours ago, strider3 said:

I'm guessing there is no way to turn off this docking port behavior, temporarily, until I'm ready to actually dock something?

Not in the game as is. That would require either a mod or a change in the game. And while I guess that this would be easier to implement than the "don't change root" issue, I wouldn't hold my breath for this to be implemented in the stock game. (Feel free to open an issue on the bug tracker though.)

6 hours ago, strider3 said:

So, friends...any suggestions going forward?

No really good ones, sorry. I'm not sure if suggestions like "launch fewer but bigger parts" or "have fewer docking ports" will actually help you.

I do have some mistrust of the modded parts, here the weldable docking ports. But this isn't based on any real knowledge and more on my ignorance of these parts.(*) So it might help to re-build the station with only stock parts, and no autostruts to root or heaviest. But a) I think you probably already tried that and b) I don't really know if it will be better or not.

7 hours ago, strider3 said:

And while I'm asking, would the "slow down" be helped with a higher performance computer

Yes, I think so. If you are low on memory, then more RAM would help, but for this it is mostly single-thread performance of the CPU. But it will only mitigate the problem not completely remove it. I.e. if the station is big enough then you'll always have slowdowns at some point. (And, no, a modern supercomputer also wouldn't help: they get their performance from having many threads, not so much from single thread performance.)

P.S. Sorry, that my comment isn't more helpful. I did think about it for a while, but I just don't have a good idea how to solve your problem(s).

P.P.S. (*) In German we have a saying "Was der Bauer nicht kennt, dass isst er nicht." The literal translation is "What the farmer doesn't know, he won't eat." but I don't know any good English equivalent of this - which is interesting on it's own now that I think about it, but I digress.

[strider3]

Plan "C". Start with a modified central stack, leaving the cupola as the Root and using only auto-strut Grandparent. Use only 2 arms with the docking ports as I didn't seem to start having issues until trying to attach the 4th (and final) arm. I want to keep the lights so I can see what I'm doing during construction on "night side". This begs a question, is there a way to turn certain banks of lights on and off while not affecting others? The other 2 arms will still be attached but will not have docking ports...I can use them as a place for portable struts if the tanks start to get "wobblies". As always keep the torque setting low on the stations reaction wheels, turn off RCS and SAS on the docking vessel just before docking.

We'll see if that helps.

[strider3]

Here's "plan C"...ongoing...so far, so good. I've reduced the amount of "open" docking ports by only putting them on 2 of the 4 arms. In hindsight my original design was overly complicated and the new design results in the same amount of fuel/LOx available. The other 2 arms are now used to store fuel (in the octo-girders they are made from) and as an attachment points for portable struts from the tanks mounted on the other 2 arms. The struts may not be necessary...but most times I've said that in the past, a Kraken visits...sooooo. I've also reduced the amount of "open" docking ports by only attaching one arm with them and then covering 4 of the ports with tanks, and welding them. In the screenshot below I've got 2 tank sets attached and will bring up 2 more before launching the other arm that has ports. The reduction of "open" docking ports seems to have been the single biggest help with the previous issues with the induced physics warp in previous station building attempts. (thanks to 5thHorseman for pointing this out, as I had NO idea).

Thanks to all and I'll post an updated screenshot once (and "if" ) she's completed.

 

[strider3]

Well, Ladies and Gentlemen...I give up. Now the station comes apart when setting one of it's docking ports as "Target" for the incoming tank hauler. Somebody will need to explain why that happens...no docking is occurring, I am simply selecting the port that I want to target. I don't understand why this "physics warp" issue has started. I have built large stations, with the weldable Konstruction ports...without any of these issues in previous versions of KSP. Is it a 1.7 thing? I have no idea.

I'm going to fire up the Xbox and go shoot something.