Fuel flow problem - help requested

[Minimalist]

Hi Kerbonauts,

I need some help with funky fuel flow. I designed a craft with ridiculously long small diameter boosters. So I thought, "Why not asparagus them and save the length?".

So I split each booster into eighths (they were very long ) and set up the fuel pipes and staging. After several failed launch attempts (<plug>using TriggerAu's excellent Alternate Resource Panel for debugging</plug>). The two fuel lines connecting the two engine stages are the only pipes installed without symmetry.

My debugging could be wrong. I could have a mis-placed fuel-line. I can't see why one works and one doesn't. Links to craft below.

This one behaves as expected.

This one doesn't.

I had to re-arrange the staging a bit between the two. One is four stage, the other eight. I did this purely by re-staging the decouplers, didn't touch the existing fuel-lines. The original had a payload, which I removed. I use a few mods (KER, RT2 - I removed the antenna, the above mentioned ARP, no others that I think will interfere).

Could any rocket boffins help stop me going crazy, please? I could just replace the whole shebang with 2 large-diameter boosters, but where's the Kerbal in that?

Edited August 8, 2015 by Minimalist
Problem solved

[Pecan]

You don't need fuel-lines between the upper/lower tanks in each stack.

More importantly the lines from each stack to the centre are wrong, only the last-jettisoned stage (2 stacks) should have those, the rest just feed via their neighbours.

Hmmm, looking at it a bit more; you've used symmetry-4 to position the decouplers. You can't do that, then try to treat them as symmetry-2 (or, if you can, it'll be a lot of hassle). Part of what makes asparagus fiddly is that you HAVE to place opposite stacks using symmetry-2.

Edited August 7, 2015 by Pecan

[MadChris48]

Part of what makes asparagus fiddly is that you HAVE to place opposite stacks using symmetry-2.

You can use 4x symmetry to build asparagus, you just have to be diligent in correcting the staging.

- - - Updated - - -

After DLing and checking them out, the one that works is just fine. Pecan is right that you don't need the small fuel lines between the tanks in each stack. Otherwise your working model does just that... it works!

The design that doesn't work needs the fuel lines removed from the boosters to the main tank, except for the last stack to be jettisoned (again, like Pecan said).

Good luck on your design!

[Pecan]

You can use 4x symmetry to build asparagus, you just have to be diligent in correcting the staging...

AND place things that don't use symmetry-4, like the fuel lines, singly instead of using the symmetry you started with, hence "if you can, it'll be a lot of hassle" in my post.

[Minimalist]

Thanks for the quick replies.

I removed the symmetry for the centre-feed lines and it now behaves sensibly. Not as I expected, but that's my understanding, not the craft .

Corrected craft.