How to fix stability problems

[SamTheShark]

My rocket has a large problem with remaining rigid in flight and the main body "wiggles" as it gains speed. I would appreciate any tips on how to remedy this.

[Aegolius13]

The easiest way is with autostruts.  First, turn on "advanced tweakables" in the menu if it's not on already.  Then, in the VAB, right click parts and click the menu option to add autostruts.  For a long, narrow rocket like this, I like to do two sets:

-Pick something near the bottom of the rocket, and have it attach the strut to the root part. 

-Then, pick something at the top of the rocket, and have it attach to the heaviest part.

This method usually works well, but sometimes you have to experiment around to optimize.  And it's best not to go overboard with these things, as in excess they can summon the Kraken.   

[bewing]

Autostruts. That's exactly what the devs gave them to us for.

 

[Snark]

4 hours ago, SamTheShark said:

My rocket has a large problem with remaining rigid in flight and the main body "wiggles" as it gains speed. I would appreciate any tips on how to remedy this.

Other than using autostruts... are those Vectors?  Vectors have a huge gimbal range-- it can drive SAS to overcorrect and result in hilarity.  You should need hardly any gimbal on ascent, assuming you're doing a reasonable gravity turn-- have you tried tweaking the gimbal way down?  Say, to 20% or so?

[Geonovast]

Of course if you don't feel like clicking on every freaking part to cycle through an autostrut option that can actually rip your ship apart if there's a root or heavy part change, there's always KJR, which also doesn't need to be unlocked in the tech tree.

 

[strider3]

I pretty much use Autostrut on all my ships. So far, I've used only "Grandparent part" for all my autostrutting needs, with excellent results...and that keeps it simple. I'm not saying "GP" will work for every autostrut/vessel situation...but I have yet to run across a situation where GP type autostruts did not work.

Cheers!

[Tyko]

19 hours ago, Victor3 said:

I pretty much use Autostrut on all my ships. So far, I've used only "Grandparent part" for all my autostrutting needs, with excellent results...and that keeps it simple. I'm not saying "GP" will work for every autostrut/vessel situation...but I have yet to run across a situation where GP type autostruts did not work.

Cheers!

@Aegolius13's approach is similar to what I do.  I autostrut the engines from each lower stage to "root". This ties the ship together really well without too many autostruts.

I avoid using "heaviest" on any craft that will be docking with another craft because that can get wonky and break ships.

 

[strider3]

4 minutes ago, Tyko said:

@Aegolius13's approach is similar to what I do.  I autostrut the engines from each lower stage to "root". This ties the ship together really well without too many autostruts.

I avoid using "heaviest" on any craft that will be docking with another craft because that can get wonky and break ships.

 

Is there an issue with using a lot of autostruts?

[Tyko]

4 minutes ago, Victor3 said:

Is there an issue with using a lot of autostruts?

I know of at least one issue - if you autostrut to "heaviest" and the heaviest part switches because a heavy fuel tank empties or you dock with a heavier craft, the struts have to recalculate their connection points and this can break things.

In general I just don't trust them entirely because of that need to recalculate occasionally. So I just reduce my risk by using as few as possible. 

[GoatRider]

Especially don't autostrut to heaviest when you're grabbing a big asteroid. I've had that go really nasty on me and rip apart my ship. Especially going in and out of time-warp, sometimes my ship was bent from the force of an autostrut that got calculated too short. The more of these struts you have, the more likely something will go wrong.

[strider3]

Thanks for the info, gang.

[Cavscout74]

I simply started using Full Auto Strut mod by @Xyphos, set to grandparent for all.  I'll occasionally switch the lower stage engines to root for larger craft, since those parts will be staged away long before any docking might take place.  So far, it's served me well.

https://spacedock.info/mod/1479/FullAutoStrut

 

[SamTheShark]

Thanks for all the information!