Bug with asparagus not draining single central tank

[magnemoe]

I made an Eve lander with an pretty unusual configuration however the basis is asparagus with 7 48-7 engines.

Stage 5 is the tank on top mostly for deorbiting, the leftover fuel is used during launch, stage 4 has 90 liter fuel, stage 3 45, stage 2 is put on top as I had stability problems using the traditional 1+6 engines design because of drag, stage 1 is the standard center stage and stage 0 is an ant and oscar for finishing circulate and meet the mothership.

Karbal stands on ladder during launch to save the weight of seat.

Now my problem was that the two stage 4 tanks was drained unevenly, or more precisely, one side used fuel from both the center deorbit tank and its own tank destabilizing the lander.

After redoing the piping without any luck I did some static tests and fond that stage 2 and 1 was drawing fuel from one stage 4 tank. not the central and shared deorbit tank.

Solved it by adding an decopler between the two 45 liter tanks on top so each stage 4 had their own. No lander did not work.

The problem was that while I needed some trust high up deep in the atmosphere the trust above center of mass caused the lander to roll then I reached 16 km, the 75 kg seperatron was also an killer.

[Johnno]

Well known issue, you're going back into the central stack after going out from it, big no no.

[MiniMatt]

Looks like the same issue I encountered a few weeks ago. Thread at http://forum.kerbalspaceprogram.com/showthread.php/46747-Uneven-fuel-ducting-when-feeding-from-one-tank has some info and potential workarounds.

[Tiron]

Well known issue, you're going back into the central stack after going out from it, big no no.

I dunno, some of my old designs did that, and it handled it fine...if and only if the symmetry coming out was exactly the same as the symmetry going in. 2->1->2? No problem. 2->1->4? Problem. 2->1->3->1->2? Problem.

I think they did mess with the logic since then though so I'd have to check.

[capi3101]

You've got a fuel loop going on; if it worked for you before, that was luck. Check out MiniMatt's link for workarounds.

[magnemoe]

Looks like the same issue I encountered a few weeks ago. Thread at http://forum.kerbalspaceprogram.com/showthread.php/46747-Uneven-fuel-ducting-when-feeding-from-one-tank has some info and potential workarounds.

Yes, look like you had the exact same problem as I had, and the solution was to divide the top into two tanks with an decouple.

However I have an many-one-one-many design who work fine, however this is an far simpler design, top tank with four droptanks where I only enable flow from two and two. two docked modules, then pipe two two side tanks, decoplers or docking port and three tank stacks with engine at bottom and that worked nice.