Weird Craft Explosion

[Voyager275]

I was launching this rocket

when everything except the first stage and the command pod exploded. The command pod was then destroyed because the first stage collided with it. It happened so fast I wasn't able to get a screenshot, but the report said all the parts that exploded first had collided. Any ideas on what happened?

Edited August 4, 2015 by Voyager275

[xtoro]

Sometimes not enough struts will cause collisions. Try removing them completely or adding more. This has only ever happened to me once, and switching from 2x to 4x symmetry fixed it.

[Sharpy]

If you have no clue what happened, press F3 and read what got destroyed first, and how.

It isn't always clear - ghost overheating or such, but sometimes it's just two clipped parts disassembling explosively.

[CalculusWarrior]

I agree, this sounds a lot like parts colliding and exploding. What levels of acceleration were you experiencing the moment the incident happened?

[cutlercollin99]

Try moving the rocket closer to the ground in the VAB. Maybe the code that brings it to the ground is messed up.

[Voyager275]

I agree, this sounds a lot like parts colliding and exploding. What levels of acceleration were you experiencing the moment the incident happened?

I was going at 150m/s and it didn't say anything about overheating after the explosion, also it hit 15g's. The rocket has never reached that high of g's, at least not that early

Edited August 4, 2015 by Voyager275

[Tatonf]

If you have no clue what happened, press F3 and read what got destroyed first, and how.

It isn't always clear - ghost overheating or such, but sometimes it's just two clipped parts disassembling explosively.

You should do that.

[Voyager275]

I read the F3 report, and apparently the skipper engine collided with the fuel tank and the decoupler, right at the moment my ship hit 15g's randomly. It also said all the other parts collided with each other, such as the monoprop tank with the launch escape system

[Tatonf]

Have you tried launching it again ? It always happen ? If so, post a pic of your spacecraft.

[Voyager275]

Have you tried launching it again ? It always happen ? If so, post a pic of your spacecraft.

I launched it again and it didn't happen. I remember it happened when I tried to launch a station core back in 1.0.2, but thought it was one of the numerous problems of that update.

- - - Updated - - -

It has happened twice for me. Once with a station core in 1.0.2 and with this craft in 1.0.4. During both flights I reached about 150m/s and then the ship hit 15g's randomly and parts not even touching each other collided and exploded. Also the first stage survived on both including the command module for both. I don't know what causes it.

[steve_v]

What's the launch TWR of that beastie? looks like you have rather a lot of thrust in the first stage, it might simply be crushing a decoupler further up the stack. 15Gs is a fair bit after all.

And yeah, that instability in the new thermal system really needs to be fixed ASAP. There are plenty of reports on the forums, but little progress on the bugtracker. Yet another new "feature" horribly buggy on launch day and subsequently ignored. Not impressed Squad.

[Voyager275]

What's the launch TWR of that beastie? looks like you have rather a lot of thrust in the first stage, it might simply be crushing a decoupler further up the stack.

And yeah, that instability in the new thermal system really needs to be fixed ASAP. There are plenty of reports on the forums, but little progress on the bugtracker. Yet another new "feature" horribly buggy on launch day and subsequently ignored. Not impressed Squad.

The way I launch is by throttling down after liftoff so the thrust shouldn't be the problem, also the rocket that launched the station core was smaller and slower than this rocket and it did the same thing.

[Snark]

I read the F3 report, and apparently the skipper engine collided with the fuel tank and the decoupler, right at the moment my ship hit 15g's randomly. It also said all the other parts collided with each other, such as the monoprop tank with the launch escape system

Right. So the issue is that your craft is accelerating way way too hard, so that it ends up "squishing" the middle stage and it goes kablooie. Therefore, the question is "what's making the craft slam on the gee-force so hard".

I can only think of a couple of potential candidates off the top of my head:

1. Something weird with clipping. I don't see anything obvious in the screenshot (you seem to have a fairly conventional vertical-stack rocket), but... is there anything "clever" about the ship construction, like parts clipping into each other in the editor, that sort of thing?

2. Are you running any mods that tinker with game physics, such as FAR, etc.? potentially some bug there?

[Voyager275]

Right. So the issue is that your craft is accelerating way way too hard, so that it ends up "squishing" the middle stage and it goes kablooie. Therefore, the question is "what's making the craft slam on the gee-force so hard".

I can only think of a couple of potential candidates off the top of my head:

1. Something weird with clipping. I don't see anything obvious in the screenshot (you seem to have a fairly conventional vertical-stack rocket), but... is there anything "clever" about the ship construction, like parts clipping into each other in the editor, that sort of thing?

2. Are you running any mods that tinker with game physics, such as FAR, etc.? potentially some bug there?

Theirs no parts that are clipped, and there are no mods that change anything that would affect the launch. It could be a new bug

- - - Updated - - -

This is a recreation launch, the screenshot taken when the stats(except the g-force) were similar to the incident.

[Voyager275]

I launched 3 of this same mission and not one of them reached that high of g's anytime during launch, so I think it might be a new bug that strikes sometimes

[Nich]

A mammoth seems like a lot of thrust for a craft that small could it have been a structural failure?

[Wolfox]

Weren´t you tilting the rocket too aggressively? In case of rocket this high with CoM in lower part, fast tilting might cause some of the decouplers to "slide" off the node. When this happens, big portion of weight would be suddenly taken off the hi-powered first stage, which would then accelerate (thus 15-G spike), ramming the separated upper half of the rocket. This happened to me several times with very high rockets with lots of vertically stacked sections. Angular forces atop rocket like this are much stronger than on the lower half due to CoM sitting in lower half. Try to use Kerbal Joint Reinforcement to prevent similar x´plosions.

[Voyager275]

Weren´t you tilting the rocket too aggressively? In case of rocket this high with CoM in lower part, fast tilting might cause some of the decouplers to "slide" off the node. When this happens, big portion of weight would be suddenly taken off the hi-powered first stage, which would then accelerate (thus 15-G spike), ramming the separated upper half of the rocket. This happened to me several times with very high rockets with lots of vertically stacked sections. Angular forces atop rocket like this are much stronger than on the lower half due to CoM sitting in lower half. Try to use Kerbal Joint Reinforcement to prevent similar x´plosions.

That's the same way I do all my PCL launches so I don't know what would've changed on this flight, especially since I did three launches today of this same rocket and they didn't explode