The Kraken is aggrivating me a little bit

[Firemetal]

Alright docking ports. In real life, when something big is docked to the ISS, it aligns itself, pushes forwards and docks. It isn't always aligned correctly but when it gets there, it just docks. I watched a video of a camera on the Cygnus and it went so smoothly.

When I dock small things, I never get it aligned correctly but it always seems to swing around and dock it and that's it. But when I try to dock, lets say, a large 3.75m dry tank, it docks and then the whole station explodes.

Here is what I mean:

Spoiler

After this, parts that had been docked previously had blown up and split apart from the station. Lets see now... Is this normal? Is this realistic? No.

I don't know. Maybe I'll make this station for kerbals only and have a refueller at the Mun or something. But for now, anyone else experiencing this or know how to fix it? Thanks.

Fire

[Dafni]

Might be an autostrut issue. Just a thought, but check for autostruts that re-strut themself after docking.

[Firemetal]

7 hours ago, Dafni said:

Might be an autostrut issue. Just a thought, but check for autostruts that re-strut themself after docking.

Nope. I double checked. Every single part was autostrutted.

Fire

Edited November 16, 2016 by Firemetal

[Dafni]

6 hours ago, Firemetal said:

Nope. I double checked. Every single part was autostrutted.

Fire

There might be your problem. One of the first things I painfully learned about the new autostrut feature: use them sparingly on stations! They are prone to introduce all kinds of madness, especially when you dock stuff together. Use them wisely, maybe one or two on key parts. Too many of them might definitely lead to problems.

[Firemetal]

5 hours ago, Dafni said:

There might be your problem. One of the first things I painfully learned about the new autostrut feature: use them sparingly on stations! They are prone to introduce all kinds of madness, especially when you dock stuff together. Use them wisely, maybe one or two on key parts. Too many of them might definitely lead to problems.

Hmmm... Ok. I will try again. Maybe...

Thanks

Fire

[Rich T]

I'm having the same problem as well. The Kracken is krack-a-lackin the fun right out of building the station. If I catch it fast enough and warp, I only end up loosing a few parts. If I don't catch it in time the station is complete loss. Is this violent sudden shaking a concern irl? Are there any definitive words on how to properly use the autostrut feature posted anywhere so we can try to prevent this from happening?

[sal_vager]

@Firemetal, @Rich T, could you please share your saves just before docking, the rest of us could take a look and see if we can come up with something.

[Rich T]

Will do this evening Sal. How would I go about sharing the saves.

 

Also, I don't know if it matters but I'm using MechJeb. However, I had a few visits from the Kracken prior to loading MJ. 

[sal_vager]

Well, dropbox is okay for files, though I really need to find an alternative as dropbox's "Don't forget to login/sign up!" messages are really annoying.

Mechjeb is not likely to be causing the issue, but I hear it's not yet updated for 1.2.1

[OrbitalBuzzsaw]

19 hours ago, sal_vager said:

Well, dropbox is okay for files, though I really need to find an alternative as dropbox's "Don't forget to login/sign up!" messages are really annoying.

Mechjeb is not likely to be causing the issue, but I hear it's not yet updated for 1.2.1

Who says either Firemetal or Rich T are using Mechjeb?

 

To @Firemetal and @Rich T, why not try the old "triple docking" trick. Works for me.

[sal_vager]

20 minutes ago, OrbitalBuzzsaw said:

Who says either Firemetal or Rich T are using Mechjeb?

 

Well, Rich T does say he's using mechjeb immediately above my post, soooo....

19 hours ago, Rich T said:

Also, I don't know if it matters but I'm using MechJeb. However, I had a few visits from the Kracken prior to loading MJ. 

Emphasis is mine but I doubt it's the issue here.

 

[OrbitalBuzzsaw]

19 minutes ago, sal_vager said:

 

Well, Rich T does say he's using mechjeb immediately above my post, soooo....

Emphasis is mine but I doubt it's the issue here.

 

Well I'm blind

[Rich T]

@sal_vager not sure exactly what you needed so I zipped and boxed the entire save folder and posted it here:

https://www.dropbox.com/s/mm8m9n0y8jgy5jh/GTF Outerspace.zip?dl=0

One of the saves is "Kracken Attack". I re-docked my mining rig and after about 5 to 10 seconds, the attack began at which point I made the save.

I hope this information helps resolve the issue as its really starting to detract from my game play experience. If it's a natural phenomenon that can be expected irl then "so be it" but some words to that effect and how to deal with it would be greatly appreciated.  If it's a bug then I suggest doubling down on the efforts to eliminate it because, as I previously mentioned, it's a huge detraction from what I believe the game play experience is intended to be.

Also, some detailed text on the intent and use of the "autostrut" and "ridged attachment" features would be greatly appreciated. While it may seem obvious to the seasoned users, it is not to this user and probably other newer users as well. Unless I missed it, searching on this forum and google doesn't really reveal much info on the features.

Thank you for your help and efforts.

[sal_vager]

Autostrut and rigid attachment are still fairly new, there's not a lot of information available, though I'm sure in time someone will post everything they've learned about them.

Autostruts were added only to wheels to begin with, and were an attempt to make them behave, several players discovered them when they saw that their stations became much more rigid after docking a spaceplane, or any craft with wheels.

They have since been expanded to be an option on nearly any part (it must have an action menu), the autostruts attach to the heaviest part in the case of wheels, but can optionally use the root and grandparent part when used by the player.

Autostruts provide a strong support from the part to the root/heaviest part, but don't provide the flexibility in placement as regular struts.

 

Rigid attachment was added as an alternative to autostruts, rather than magic invisible struts solidly securing a part to the root etc, rigid attachment increases the strength of attachments between parts, and allow for some 'give' or flexibility in the joints, several rigidly attached parts can still bend or sag, but to a much lesser degree than regular part attachment.

One use for these is with the T38 decoupler, which used to be physicsless so it wouldn't wobble, however this caused the game to crash on OSX when this decoupler was staged, now it is a physics part and rigid attachment makes it usable.

 

Of the two, rigid attachment is simpler, strong enough for most uses and is designed with large heavy vessels in mind, autostruts were a workaround which has been dressed up with a UI, and unless you cannot make your craft work using rigid attachment or regular struts I recommend that autostruts are avoided.

 

I personally prefer the good old fashioned strut, as its properties and the control they give me are fine for all my designs, whatever the size.

[sal_vager]

Okay @Rich T, I can fix your ship, though it's only by using the very same autostruts I recommend against...

To answer the questions above though, this is not a normal real world phenomenon, it's a bug, but there's a problem.

This particular bug appears to be in the Unity joints themselves, which use PhysX for their physics, and while they behave most of the time under some conditions they can start feeding motion back into each other.

Here's my demonstrator in 0.19.1

 

And another in 1.2.1

 

This seems most likely to occur with several relatively light long parts, it can also manifest when solar panels are extended, and when a long vessel is low on fuel (it's lighter).

Stations seem to be prime targets too.

Unfortunately, stiffening the joints has no effect, whether using KJR or the new joint reinforcement, modifying the joint values in the Unity editor also doesn't prevent this.

The only things that work are to strut vessels that show this behaviour, the feedback still occurs but parts are prevented from moving further than the struts will allow, and to increase the mass enough so that these vibrations dampen out.

Now that we have autostruts we can abuse them to save our stations from the PhysX Kraken, and I saved your space station by finding all instances of autostrutMode = Off and changing them to autostrutMode = Root

You can find the autostrutted save file here.

This may have left some of your other craft somewhat rigid, but they are likely going to still work unless they relied on being flexible.

Most of the time the above just doesn't happen, and PhysX in Unity is a bit of a black box, you can get the current position and velocity of the parts as they are flailing around but not why this force is being applied to them.

Any explanation would be a guess and the damper values should be preventing this, I do know though that PhysX is 32bit, so integer overflow might be occurring here, but without debugging PhysX itself I can't know.

 

[Rich T]

Wow @sal_vager that's a lot for a newbie to wrap his head around. But I'm sure playing long enough eventually the light bulb will light and I will understand. I appreciate your efforts.