Ship starts wobbeling without any reason

[Malior]

Hello,

actually, I hope that this is the right place in forum for it.

I am having trouble with my space ships all the time. Some ships suddnely starts wobbeling more and more and then break.

I have made a video and uploaded here (private link): https://youtu.be/GsvHPFlOyoY

I often have constructions, which have stages, looking like that, and often it ends up wobbeling  and makes further flying impossible without "skipping" this stage at all.

Currently I am not sure about conditions that may cause that, but as you maybe saw, there is no wobbeling right at the beginning. My guess is, that the amout of remaining fuel is respondible... anyhow.

It's the version : 1.3.0.1804

 

Malior

[Chel]

I have three questions for this, and by answering them, I can give you help.. Are you using mods? If so, then it could be an issue with the mod (for example Firespitter used to glitch out, tearing off plane wings and sending my craft at extremely high speeds). Does this problem occur with all your ships? If it does, then try launching a stock craft. And finally, have you edited the game files in any way? That could cause issues.

[Malior]

- No mods, that are (shouldn't) effecting game physics. Just for information or something like that. Anyway, I've deactivated them and can observe the same issue. (I also checked game files, there were 1980 files replaced)

- No, not all ships. I think it's related having a ship with just two symetric side elements. Maybe position of struts also important. I've uploaded the ship which is visible in demo:

Wobbeling.craft

When you try this, Just set the orbit of sun, and accelerate a little. maybe its just because of the amount of fuel. then activate SAS and RCS. Then often it starts. From then on, it cannot be stopped. even switching SAS or RCS off.

 

 

 

Edited October 2, 2017 by Malior

[Chel]

So you're using the KSP demo version? Then it's pretty simple: You're getting attacked by the Kraken. The Kraken was fixed in version 0.17, but the demo version is before 0.17, which means that Kraken attacks still happen. There isn't really much that we can do about that, as there isn't really a way to stop the Kraken from glitching out your ships. It was only fixed in 0.17, and SQUAD doesn't do updates to the demo version anymore.

[Jas0n]

I would try making the side boosters out of a single tank and attaching it directly to the decoupler instead of having a modular strut in between. Also try having struts at both ends of the booster so the oscillation can be countered. 

1 hour ago, The_Cat_In_Space said:

So you're using the KSP demo version?

He says it's 1.3.0.1804. And there was definitely a 0.18.3 demo, and probably a newer one.

[Malior]

Kraken? Demo? No ;D

Have you tried the ship I posted on your own?

@ Jas0n, when adding some more struts it looks like not wobbeling any more... at least not with increasing. (I dont have the large single tank yet)

 

 

Edited October 3, 2017 by Malior

[Val]

Moved from Technical Support.

[steve_v]

If this is what I think it is, and mods are not involved, then there are a bunch of bug reports for it already- going way back to the earliest KSP releases.
The physics engine is janky as hell, and goes berserk with certain combinations of heavy parts attached to light parts.
Like all the other game engine related glitches, it's squarely in the "too hard" basket and nobody is interested in fixing it.
The only workarounds I am aware of are to either change the craft geometry or add more struts.

Alternatively, try KJR. It may help, it may not.

Edited October 3, 2017 by steve_v

[bewing]

Looks more like an autostrutting issue to me. Are you using autostruts?

 

 

[Malior]

What are autostruts?

@Steve_v: Yes, I've adde more struts, and then it looks like not happening any more.

Actually, I am not blocked any how with this. I had the issue for some flights, and had to revert them.. no big deal. I mostly wanted to point on the problem. I thought it could be just a sing error when damping the vibrations

[Spricigo]

4 hours ago, bewing said:

Looks more like an autostrutting issue to me. Are you using autostruts?

That was also my first impression.  But seems the more rare case when it happens without autostrus.

@Malior autostrut are like normal struts but have no mass, no drag and no cost. You need [allow advanced tweakables] enabled ob settings to be able to use autostruts. Then, in the right-click window you can chose for each part how to set autostrut (disabled/heaviest/root/grandparents) and an autostrut will link the part in question to the relevant part. Whell are an exception, always autostruted to heaviest part*.

As you craft is affected by forces, including the ones caused by the interation between the parts it may flex. As it flex the forces are recalculated and reapplyed. Depending on how those forces varies it can enter in resonance, the reault is an oscillation that becomes bigger and bigger until the ship break appart. 

That is not exclusive to when autostrus are used but is oftaten associated with autosstruts because it increase the chance of that happening because autoatruts 1) add more links with associated varying forces and 2) autostruts force can suffer wider variation because of the larger distance between the parts.

Other than using rigid attachment (what can make the craft brittle) you can deal with the problem increasing or reducing the connections between parts, or just changing the connection. (Whatever  takes to avoid the problematic frequency the forces vary)

*I know why we don't have the option yo disable it (autostruts was originaly to deal witg wheels issues) . My question is why we can't autostrut wheels to grandparent/root? Glad if someone can provide that info.

 

[Palaceviking]

All hail the mighty kraken!! 

[agrasyuk]

it looked like your ship was simply jiving to the music you put . and i must say it was looking awesome doing it

i hope this gets resolved for you