Failures - Bug of Feature?

[SpaceHole]

Im not exactly sure if this is fot the bug-section or a general discussion? (may a mod move it if its a bug)

Lately since i do bigger spacecrafts i often run into odd problems:

- Rockets randomly disintegrate on the ramp (i start a game everything is normal, restart mission rocket desitegrates, restart mission normal again etc.)

- Parachutes randomly fail - i did about 8 flights with one of my rockets most of those flights ended up back on Kerbal yet from lets say 6 landings with parachute 2 suddenly failed and the parachute just stopped working a few feet above ground

So i started reading in the forums if there were built in random errors etc. but it seems there werent. So i started to wonder is this a bug or am i doing something wrong?

(the log always says something with "Structural failure")

I would be sure that its my fault when this would happen every time with the same ship yet it works most of the time and just doesnt work sometimes which is odd.

[boxman]

in 99% of the cases it is a strut/design problem but in rare cases such errors seems to happen with large crafts if you run out of memory.

And about parachutes... Did you use time warp? Using time warp when deploying parachutes makes this happen. Also make sure you deploy the parachutes when you are high up, as they slow you down even when they dont fully deploy and make sure you also have drogue chutes on larger crafts.

You would also want the speed to be lno more than max 200m/s or they can ripoff when they deploy fully at 500 meters above surface.

[Tex_NL]

"Failure is not an option! It's part of the design process."

[Sean Mirrsen]

Currently there is no random failure mechanics that we know of, so it's safe to say that any and all random failures are completely emergent. They occur due to design quirks, low margins of error, and unfavorable alignment of planets, pretty much like in real life. So... half and half. Half bug (in that it's unintended), half feature (in that it kind of simulates IRL behavior).

[SpaceHole]

Yeah i think i used the fast forward at times - so this could actually cause some of those things?

Hmm it would be nice to see problems in the design anyone of you knows the bridge-builder?

So for the time beeing i can only not use fast forward so often, open the parachute early and try to use more support structures?

[Geschosskopf]

- Rockets randomly disintegrate on the ramp (i start a game everything is normal, restart mission rocket desitegrates, restart mission normal again etc.)

I think what happens here is that when the rocket 1st spawns, it's slightly above the ground. It hangs there for a short while as the physics get going and the live feeds for the crew start to come on, and then it drops. The big grating on top of the Launchpad has both rigidity and clipping issues, so the "drop test" can cause the rocket to bounce, lean over, and/or wobble a bit, causing off-axis forces in unpredictable directions and amplitudes. And these forces, plus the rocket's own weight even if it doesn't bounce, are effectively impact loads applied all at once. So it's not surprising things break sometimes.

- Parachutes randomly fail - i did about 8 flights with one of my rockets most of those flights ended up back on Kerbal yet from lets say 6 landings with parachute 2 suddenly failed and the parachute just stopped working a few feet above ground

Were you using rockets to help slow you down? If so, you have to be careful never to totally stop your downward velocity or even start back upwards. When you do this, parachutes go away the instant your vertical velocity reaches zero because they think you're on the ground.

[Johnno]

So i started to wonder is this a bug or am i doing something wrong?

(the log always says something with "Structural failure")

I would be sure that its my fault when this would happen every time with the same ship yet it works most of the time and just doesnt work sometimes which is odd.

It's down to your designs, they're not bugs. Your crafts have weak points where they break because of physical stress, a simple test would be to mount something small on launch clamps and then a small fueltank on top of it, then stack a few large tanks above. You'll see the large tanks crush whatever's below them because of their mass (physics at work). So you simply have to reinforce your builds and/or not stack a lot of mass ontop of smaller components.

As for parachutes, don't use physical timewarp when they're about to deploy (500 meters) nor when about to touch down. Also put them on the heaviest piece or decouple your pod beforehand, the shock of deployment will rip stuff to shreds. They need to be well balanced and there has to be enough of them to slow crafts down for soft landings, that's also down to design (and testing thoroughly).

And this stuff happening 'randomly' is down to how on the edge of failure your rocket is, there's no onetime calculation to see if your rocket breaks or not when it's on the pad, there's constant physics calculations being done and even the most miniscule of changes to your ship can make it break. During flight it will be depending entirely on your throttle/direction as that'll introduce different physical stress on your craft.

[FITorion]

physics warp (time warp when in an atmosphere or near a planet) can do weird things.

here read this thread (it's short) http://forum.kerbalspaceprogram.com/showthread.php/46730-Just-one-question-for-SQUAD

[Guest]

An otherwise flight-worthy design can just randomly destroy itself when the physics starts up. Last night I launched the same craft several times and it made it to space thrice. Sometimes I would start a launch and as soon as the physics kicked in the craft would snap in half. Other times the craft would endure all manner of oscillations and bending on its way to space, and make it there safely. I tried all sorts of things; clicking different inputs at different times, changing the camera angle, adding struts (interestingly, this seemed to make the problem worse), etc... Nothing worked consistently. The craft either launched safely or killed itself.

In cases like that it is best to identify the root cause of the problem (those 2.5m SAS modules, for instance, are terrible stack pieces and were the failing point in all the launches I mentioned; avoid them at all costs) and redesign the craft.

[pa1983]

Ever sens 0.21 engines and some times fuel tanks seems to "float" around and wobble clipped or not. Bit odd never did that before.

Also random so going back to hangar and launch again solves it. Only mod I have rigth now is univers replacer but thats not at fault I just started trying it out so happened before that in a clean 0.21.