Parts breaking in 1.4.5

[Cavscout74]

After updating to 1.4.5, I'm having an issue with a large ship breaking between the upper stage fuel tank (Kerbodyne S4-128 from DLC) & fairing base (5m AE-FF5 also from DLC).  I've launched this ship multiple times in 1.4.4 & earlier without too many problems but now it breaks every launch, in the same place.  Also, hitting f3 after the break doesn't show any failure message, just the liftoff & whichever staging steps have occured.  The launcher is a 5m core with 2 pairs of radial 3.75m boosters, asparagus staged.  I can get through the first pair of radial boosters, then sometime during the second pair of radials or during the core only, the break occurs.  Altitudes have varied between 15km to around 30km

Has anyone encountered anything similar?

[Gargamel]

The ksp.log should show some details...

[JoE Smash]

Enable advanced tweakables in settings and then autostrut said faring weak spot so the ship no longer breaks.

Farings are often weak spots on my ships if I don't autostrut.....sometimes the thing inside the faring wobbles back and forth until it snaps off....

[Cavscout74]

8 hours ago, JoE Smash said:

Enable advanced tweakables in settings and then autostrut said faring weak spot so the ship no longer breaks.

Already done, just about everything is autostrutted to grandparent.  I use Full Auto Strut mod to (usually) keep things like this from happening.  I had even added regular struts from the radial boosters to the upper stage tank, since the radials were very wobbly - but they were added after the first explosion or two.

 

17 hours ago, Gargamel said:

The ksp.log should show some details

I wasn't able to post the log anywhere last night - a delivery truck that was too big for my little side street took out my cable & nearly took out the electric too.  I'm on my work computer now.  But I found a message in the log that the tank collided with the fairing, but I didn't see anything that pointed me to a reason.  And normally parts collisions are reported in the F3 window, and it's not - that was originally what prompted me to post the question.  I'm used to stuff breaking, especially on over-sized designs, but this is breaking weird & not reporting it.  I've generally been flying this as close to prograde as possible on ascent to minimize side loads, and using a slower gravity turn to get out of the thick air quicker.  I'll have to try it in sandbox the next time I'm on & get a fresh log.

[Gargamel]

4 hours ago, Cavscout74 said:

But I found a message in the log that the tank collided with the fairing,

Autostrut it to heaviest part.  Should hold it in place until that main stage drops away. 

[JoE Smash]

7 hours ago, Cavscout74 said:

Already done, just about everything is autostrutted to grandparent.  I use Full Auto Strut mod to (usually) keep things like this from happening.  I had even added regular struts from the radial boosters to the upper stage tank, since the radials were very wobbly - but they were added after the first explosion or two.

 

I wasn't able to post the log anywhere last night - a delivery truck that was too big for my little side street took out my cable & nearly took out the electric too.  I'm on my work computer now.  But I found a message in the log that the tank collided with the fairing, but I didn't see anything that pointed me to a reason.  And normally parts collisions are reported in the F3 window, and it's not - that was originally what prompted me to post the question.  I'm used to stuff breaking, especially on over-sized designs, but this is breaking weird & not reporting it.  I've generally been flying this as close to prograde as possible on ascent to minimize side loads, and using a slower gravity turn to get out of the thick air quicker.  I'll have to try it in sandbox the next time I'm on & get a fresh log.

Well....not to ask an insulting question, because it sounds like you have a relatively advanced understanding of ship design and launching technique....but

Are you also keeping your thrust to weight ratio under 2 during the lower atmosphere?

I usually try to limit the throttle on my SRBs in the VAB to like 1.5 for the TWR at least until they are beyond severe atmospheric resistance....so stuff doesn't shake violently or heat up excessively....

I figure you are doing that as well, but you never know until you ask....

[Cavscout74]

15 hours ago, JoE Smash said:

Are you also keeping your thrust to weight ratio under 2 during the lower atmosphere?

IIRC, the TWR is about 1.4 or so off the pad, and drops to around 1.4-1.6 each time I drop a pair of radial boosters.  There's a brief period I throttle down a little below 10k, but the first pair runs dry shortly after that

It is admittedly a huge design, and is difficult to launch at best, but it launched in 1.4.3 & 1.4.4 as long as I was careful..  I may try redesigning the fairing, see if I can get a cleaner shape on it - originally I was trying to keep it as small as possible, but that created an odd shape, so maybe trying for a more uniform shape would work better.

Also, I've been messing with a game copy with a few different mods, so I haven't tried my main game (with this design) since I asked the question.   I need to fire up my main copy & do some more testing.

 

***Edit:   I just realized, I made the payload heavier between 1.4.4 & 1.4.5.   Not a huge amount heavier, but enough so that I had to add some fuel to the launcher & change engines on one pair of radial boosters.   I need to see if I still have the original design saved somewhere

Edited August 24, 2018 by Cavscout74

[Cavscout74]

And I had a chance to pull up my old version & launch it in 1.4.5 and guess what:   I made it.  Almost.  It still broke - at the engine plate this time.  But it broke at around 45km, when I got a little too aggressive trying to pitch up a little to bump my Ap above 70km before my lower stage ran dry.   I also noticed some of my life support tanks had the wrong materials in them in the old version, and I don't know how the densities compare, so I could have had more mass there too.  So between different materials in the tanks, extra payload weight & a lumpier fairing, that combination is the probable cause of the break, not a change in 1.4.5

[JoE Smash]

2 minutes ago, Cavscout74 said:

And I had a chance to pull up my old version & launch it in 1.4.5 and guess what:   I made it.  Almost.  It still broke - at the engine plate this time.  But it broke at around 45km, when I got a little too aggressive trying to pitch up a little to bump my Ap above 70km before my lower stage ran dry.   I also noticed some of my life support tanks had the wrong materials in them in the old version, and I don't know how the densities compare, so I could have had more mass there too.  So between different materials in the tanks, extra payload weight & a lumpier fairing, that combination is the probable cause of the break, not a change in 1.4.5

Well I'm glad the mystery is solved....

I find it pretty amazing the things I have managed to get into space.....like my first space station....that thing was riduculous. I didn't feel like doing a bunch of docking assembly so I just threw a huge faring over it and launched it with a 6-way hub in the middle and four future construction trusses with tanks in the middle of the trusses. It had a science lab on one end with a ZZZ radio telescope attached to it and a fuel tank with a cupola on the far end. The faring was as big as the launcher....

It needed some struts to stabilize what I had inside the faring, but I got it up there....by my third or fourth design tweak....

Procedural farings FTW....

[Gargamel]

If the payload tank is still wobbling, you can try to old method of strutting, like by using struts.    Inside the fairing, attach 4-6 of them in symmetry, and bring them up to the bottom of the payload, or where ever is appropriate.    When the stage drops away, it will take the struts with it. 

[JoE Smash]

14 hours ago, Gargamel said:

If the payload tank is still wobbling, you can try to old method of strutting, like by using struts.    Inside the fairing, attach 4-6 of them in symmetry, and bring them up to the bottom of the payload, or where ever is appropriate.    When the stage drops away, it will take the struts with it. 

Yeah that's basically what I did, but I didn't explain it as clearly....

Can't gave giant things wobbling inside the faring...