Glitches in VAB and problems with balancing air-breathing engines

[g00bd0g]

So I am trying to build a re-useable launch vehicle using Rapiers. I have built several successful ones, but as of late, I have been having big problems.

1. After messing around with a design in the VAB for a while I invariably end up with a "glitched" build. This usually results in a corrupted vehicle file and frequently crahses KSP.

See "VTOL 5" for an example.

https://drive.google.com/file/d/0B4zLBUio4kInYk9HTTZKZnRZTG8/view?usp=sharing

2. Even after an apparently successful build. I have yet to build a craft that "balances" the air to the engines properly. i.e. I would like each sucessive "ring" of engine to flame out together. Instead I usually end up with one "arm" going 1st, but I have had crazy distributions with seemingly random flame outs across all engines.

See "VTOL 7" for example.

https://drive.google.com/file/d/0B4zLBUio4kInZlJ2Vy1CbWdVRXc/view?usp=sharing

Of course this results in an uncontrollable vehicle and subsequent death.

Is there a "proper" way to built a craft like this? i.e. build out one "arm" completely and then apply symmetry? Or apply symmetry to each part as I am building?

Are there "rules" to generating proper air distribution?

Thanks!

PS. I know this is for "unmodded" support but I only have mechjeb/chatterer/KAC installed.

Edited November 28, 2014 by g00bd0g

[Padishar]

Kasuha has posted a very detailed explanation of the resource flow rules, including details on how "intake air" is distributed between engines (basically, it is heavily dependent on the order the intakes and engines are added to the craft). See the last part of the first post and the various other experiment posts it links to.

[g00bd0g]

Thanks! That helps with my 2nd issue.

[Padishar]

Your first issue is, unfortunately, due to bugs in the stock game editor code which is usually attributed to the symmetry handling. There is usually little that can be done other than restarting your build (though saving your craft regularly with a different name during construction can help to reduce the amount you have to rebuild). Hopefully the editor improvements coming in 0.90 will fix some of these bugs...

[Claw]

Symmetry is a bit wacky sometimes. There are a few common ways that can cause the overlapping part explosion that you're describing.

Symmetry-in-symmetry (I call it recursive symmetry) is touchy but manageable. I build like this a lot, but you have to be mindful when making symmetry of part trees that have symmetry in them. Especially if you had to do anything unusual to get the symmetry to happen in the first place.

The really bad one is having ALT+F12 part clipping on while dealing with symmetry. You can run into situations where the editor will overly multiple copies of a part on a single node (because you told the game to let you do that). If you attempt to do more symmetry, things really go haywire. If you're going to do clipping with symmetry: turn on the clipping, do your attachment, turn clipping back off.

These are even worse if you use the "undo" feature. In general, I advise against using undo at all.

Cheers,

~Claw