Parts Disconnecting Unexpectedly on Launch

[Brigadier]

I've built and lifter and lander for Mun exploration. The lander was created as a sub-assembly and inserted. When I launch, the first stage fires correctly but the lander's engines also detach causing catastrophic launchpad failure.

I've rechecked the staging and it appears correct (i.e. the lander engine decouplers are nowhere near the first stage), and I've rebuilt the lander descent stage. Neither effort changed the behaviour. Prior to this, I've successfully launched crewed missions to Mun and Minmus using a similar rocket. I've taken screen shots, I hope you can access them and the .craft files below.

KSP Version: 1.0.4 Installed Modules:

- ActsEW 1.5

- AGExt 1.33a

- AlternateResourcePanel 2.7.3.0

- AstronomersPack-Clouds-High Interstellar.V2

- AstronomersPack-DistantObjectEnhancement Interstellar.V2

- AstronomersPack-PlanetShine Interstellar.V2

- AstronomersPack-SurfaceGlow Interstellar.V2

- CapCom 1.2

- Chatterer 0.9.6

- CommunityResourcePack 0.4.4

- CommunityTechTree 2.1

- ContractConfigurator 1.7.6

- ContractConfigurator-ContractPack-SCANsat v0.5.2.1

- ContractsWindowPlus 5.3

- DistantObject v1.6.2

- DMagicOrbitalScience 1.0.8

- DockingPortAlignmentIndicator 6.2.0

- EditorExtensions 2.12

- EngineLighting 1.4.0

- EnvironmentalVisualEnhancements 7-4

- ExtraPlanetaryLaunchpads 5.2.2

- FirespitterCore v7.1.4

- KAS 0.5.4

- KerbalAlarmClock v3.4.0.0

- KerbalEngineerRedux 1.0.18.0

- KerbalStats 2.0.0

- KIS 1.2.2

- ModuleManager 2.6.8

- NavballDockingIndicator 7

- Olympic1ARPIcons 0.6.0a

- PlanetShine 0.2.3.1

- PortraitStats 6.0

- ProceduralFairings v3.15

- QuickGoTo v1.20

- QuickSearch v1.13

- RasterPropMonitor v0.23.1

- RasterPropMonitor-Core v0.23.1

- RealPlume 1:v10.4.9

- RealPlume-StockConfigs v0.8.1

- SCANsat v14.2

- ScienceAlert 1.8.9

- SmokeScreen 2.6.9

- TacFuelBalancer v2.5.1

- Toolbar 1.7.9

- TransferWindowPlanner v1.3.1.0

- UKS 0.31.10

- USI-LS 0.1.5

- USITools 0.5.1

- xScience 4.10

https://www.dropbox.com/s/gcxrfduac4r6u52/Mun%20Lander%20II.craft?dl=0

https://www.dropbox.com/s/y3otejmubne32pg/Lander%20Mk%20IIb.craft?dl=0

https://www.dropbox.com/s/n7lxb7r6vqbs3pi/screenshot25.png?dl=0

https://www.dropbox.com/s/jhmxi9u9axg4982/screenshot26.png?dl=0

Edited October 13, 2015 by Brigadier

[MennoLente]

Okay, I might have helped by recreating the circumstances and using the craft file, but I rather play KSP than wasting a few hours installing mods, so many that things are doomed to fail. So spare me the trouble and go figure it out yourself. Sure you don't want to break your save file, so try this until the problem doesn't occur anymore:

- reduce your rocket by making your part count as low as possible, with as little number of mods necessary. Does the problem still occur?

- install a second ksp (for testing purposes) in a different directory. Drop your craft file there. Install necessary mods for the craft file. Does the problem still occur?

- reduce your rocket to a completely vanilla state, and uninstall all mods. If the problem still occurs, than we can surely help you with your craft file.

So I guess we'll see you back in a few hours?

[Brigadier]

- reduce your rocket by making your part count as low as possible, with as little number of mods necessary. Does the problem still occur?

- install a second ksp (for testing purposes) in a different directory. Drop your craft file there. Install necessary mods for the craft file. Does the problem still occur?

- reduce your rocket to a completely vanilla state, and uninstall all mods. If the problem still occurs, than we can surely help you with your craft file.

So I guess we'll see you back in a few hours?

I've installed KSP via Steam. Rhetorical question: How do create a 2nd install? Hmmm, more experimentation! The rest makes sense and it'll be more than a few hours.

[MennoLente]

Unrhetorical answer;): Hmmm... Steam... That's unfortunate. Uhm... Go to the game directory, copy the entire folder, paste it somewhere else should do it, and launch by doubleclicking ksp.exe, that should do the trick. But does the problem still occur when using only vanilla parts? When something stinky hits the fan, and the cause is unknown, reduce the problem to the core, so we can fix it.

Something you should take a look at is to make sure that parts aren't clipping into each other. Even if it isn't visible, the (invisible) collision boxes might overlap, causing annoying problems like decouplers not detaching correctly, or parts exploding randomly. So when you attach parts keep clearance from other parts, and pay extra attention when attachment nodes are close to each other, like with decouplers, beams, panels, radial elements, etc.

The first thing I would look at in your case, would be a decoupler clipping into the engines. Let us know when you've found something. I look forward to hearing how it went.

Edited October 12, 2015 by MennoLente

[Brigadier]

Unrhetorical answer;):

Thanks! I didn't know if it was that simple. It also occurred to me that I don't run the game through Steam, just purchased through them.

Hmmm... Steam... That's unfortunate. Uhm... Go to the game directory, copy the entire folder, paste it somewhere else should do it, and launch by doubleclicking ksp.exe, that should do the trick. But does the problem still occur when using only vanilla parts? When something stinky hits the fan, and the cause is unknown, reduce the problem to the core, so we can fix it.

Ok, trying this. Copying was easy, configuring CKAN to point to another instance was straightforward and, removing unwanted/unnecessary mods trivial. Now to run the game...

Something you should take a look at is to make sure that parts aren't clipping into each other. Even if it isn't visible, the (invisible) collision boxes might overlap, causing annoying problems like decouplers not detaching correctly, or parts exploding randomly. So when you attach parts keep clearance from other parts, and pay extra attention when attachment nodes are close to each other, like with decouplers, beams, panels, radial elements, etc.

The first thing I would look at in your case, would be a decoupler clipping into the engines. Let us know when you've found something. I look forward to hearing how it went.

I will investigate this as well. I've already removed the procedural fairing and that didn't help. If I strip the sub-assembly out, it'll probably work and I'll proceed from there but I haven't yet figured out how to add only portions of the lander sub-assembly back in. I did have problems with getting the lander engines to attach in the first place, so perhaps you're right.

My first thought was that for some reason the lifter and the lander first stages were being triggered by the same staging command. Just a WAG, though.

EDIT: I duplicated the problem on the launchpad with just the lander and believe that completely removing and replacing the decouplers has solved the problem. I discovered this in my test KSP installation and replicated the fix in the "live" installation.

With many thanks, you've provided me with another tool to fix my own problems.

Edited October 13, 2015 by Brigadier
Update

[MennoLente]

(...) another tool to fix my own problems.

Yay! Succes! This just might save you a lot of frustration, bottles of booze and a broken keyboard. And even the problem was solved as well!

I'm happy I was able to help a bit, it was my pleasure.