Question regarding staging and very high part counts

[Archgeek]

Is it common for decouplers on very high part-count ships in the same stage to not fire at once but instead only fire one of them, repopulating the stage with the remaining decouplers?

There exists a chance that this issue has come up before, but keyword searches are ineffective at phrases like "high part count staging glitch", and I'm finding the nature of it quite odd so I must inquire if this takes place frequently.

I've got a 700+ part behemoth of a single-shot Eve vehicle with asparagus'd lander/return vehicle, 6x LV-N transfer drive and orbital xenon repository, and a loathesome dual-stack onion'd thrust plate lifting platform with 38 half-size kerbodyne tanks half with 12 KS-25x4s and 7 KR-2Ls lifting 6 mainsails and 13 more KR-2Ls in turn lifting the rest of the ship. It's staged so the lower outer stages drop and the upper outer stages light, dropping upper stages as they run out of fuel and with each tier separately feeding into its respective centre.

The physics rate is about 5 seconds per real second at liftoff, but it otherwise works, save for the glitch in question, which can oddly be worked around by pressing the stage button once for every decoupler in the stage. More strangely, this only seems to affect ditched stages taking fairings with them when under very high part count, as the upper stages detach all at once in a nice ring, as do the engines above, and the lander seen above stages just fine.

Also of note, I've got minimal mods -- just alarm clock, enhanced nav ball, engineer, and hot rockets. I am curious if this happens to others with any frequency, or one of my mods is acting up somehow.

Edited September 4, 2014 by Archgeek

[Kasuha]

No, decouplers should not do that, it seems to me it is some kind of bug. There were problems particularly with this decoupler in previous release, these seem to have been fixed but it seems like some other problems with it surfaced instead.

[Benaiah]

I run almost no mods and I have the same problem with the largest sized decoupler. Other sizes work fine.

[Archgeek]

Well that's just curious. I'll have to test it with rockomax decouplers and see if that both fixes the problem and makes the lifter look dumb. Good to know it doesn't have anything to do with insane 3-dimensional asparagusing in the lander above or some insanity.

[Archgeek]

Welp, after a lot of testing, I've found that switching to Rockomax decouplers solves the issue for the craft in question, but I also cannot reproduce the issue in anything else. The (all stock save for hot rockets) lifter on this crazy thing is nearly identical to the one in the above, and the glitch refuses to appear. It's apparent that the fairing coming with the decoupler doesn't matter (as I tried with several engine types), the part count amazingly doesn't matter, as putting very part-dense subassemblies on the test craft wouldn't cause the glitch, nor would tearing most of the craft off the lifter in the original ship make it cease.

More oddly, this may in fact be a good bad bug, as the weird decoupling behaviour lacks that inward pivot issue one sees these days.

[Clockwork_werewolf]

I often found it was Launch Stability Enhancers that were the big problem. On a very large with 32 of them or some number like that some would not detach at the same time. The engines would fire up and the ship would rip itself apart as one side is tied down and the other rockets upwards. The only Fix I found was the exact opposite of your problem. I would place decouplers under the engines and LSE's under those. The ship on the pad was held better as this didn't cause the ship to bend inwards which happens with outside attached LSE's so that I would only need a decoupler per large stack and maybe a few to hold the middle or top of the ship steady. This reduced the change of a LSE's not detaching and meant on the bottom ones it was reliable decouplers that detached (never had a problem).

[Jett_Quasar]

I have had trouble with multiple 3.25 diameter in-line decouplers not firing. It seems they are set up to only fire a single decoupler for that size. I don't think it's related to part count because I've seen it on several of my designs that weren't whackjob.

JR