Complex fuel line setup. This is just strange.

[Motokid600]

So this is my interplanetary tug which will take a lander, rover and return ( Cm Module ) craft to Laythe Orbit. All is well except the fact that im scratching my head on what to do with my fuel lines. What I have here should work. It doesn't.

What you see here is asparagus staging. Each tank drains into the next. All engines burn exepct for the center return craft. These ten nuclear engines drain the outter, smaller radial tank. That decouples then the inner, smaller tanks which then drain into the large workhorse tanks. ( The small tanks are more or less nuclear boosters ). Then the four large tanks ( still asparagusly staged ) fall off two at a time. At this point im well into Laythe's orbit. Problem? ..none of this works. At all.

Heres the staging/fuel line setup.

Heres the problem.

The highlighted adapter tanks you see here are draining...WHY?! its just these two and nothing else. For some reason its almost as if the nova punch reaction wheels in between are acting as if they are NOT crossfeed capable. They are... the other two work perfectly. All engines fire and the fuel from those non-highlighted tanks does not drain. It does exactly what asparagus staging does best. But for some reason the other two engines will drain those highlighted tanks and flame out..they wont even start taking the fuel from tank above the reaction wheel. They just cut off after those are done. So because of this it sends the whole setup out of wack. The radial engines that are supposed to dump into this engine do not and flame out not long after the highlighted ones do. The other set...again is fine. W..T...F is going on here? Ive tried jumping the two tanks with a fuel line.. no change. Something is wrong. I just don't know what. Idk if somehow the other tanks from the return craft are messing it up somehow? That craft is designed asparagusly aswell, but no fuel lines connect the tug and the return craft.

Ive been working on this craft for weeks. So this little, stupid annoyance is really eating at me. Does anyone have any idea of how this could be happening?

Edited August 6, 2013 by Motokid600

[BostLabs]

I'm no rocket scientist (hehe snort) but I think, if I'm reading this correctly, the reaction wheels are not cross fuel capable. I don't have the game with me right now so if I'm wrong I'm sure someone will correct me.

Can you put the reaction wheels on top of the tanks instead of between the tank and the engine?

[Motokid600]

well according to the description they are. That could be wrong of course, but then why do the other tanks perform flawlessly? Its as if the reaction wheels above the highlighted tanks are not CFC yet the other two...are? And no I cant put them on top because they need to be as far from the center of mass as possible to help maneuver this beast without the use of mass amounts of RCS.

[Lebowsky]

Tank 3 gives fuel to tank 4 so the fuel burns uneven. Either remove the fuelline between tank 3 and 4, or link tank 3 + 4 to the one in the middle (if returncraft fires engines from the start).

[Captain Sierra]

For starters, what mod packs are being used here? I can clearly identify B9 and KW rocketry. Perhaps you could publish a list of mods and the craft file so we could download and work on it, perhaps solve this.

Also, the problem I am seeing is that the fuel lines are at the top of the stack. Fuel lines need to be placed on the bottom tank of a stack because of the way fuel drains. Try that, then publish if that doesn't work.

[sojourner]

Also, the problem I am seeing is that the fuel lines are at the top of the stack. Fuel lines need to be placed on the bottom tank of a stack because of the way fuel drains. Try that, then publish if that doesn't work.

I have never had a problem putting fuel lines towards the top of stacks on my asparagus launcher.

[Motokid600]

Well to be honest I JUST added the lines between 3 and 4. Havent had the chance to test it yet. And no the return craft engines do not fire from the get go. So even before the large 4 tanks were linked for asparagus this was still the problem.

Nova Punch

KW

B9

HOME

and..others. Ill see once I can and upload a craft file.

[Motokid600]

Ok here we go

http://www./?p55891rva9xkaeb

Theres the craft file.

You'll need

Nova Punch

KW

B9

HOME

Eng Redux.

sorry I forgot to add launch clamps and delete the redux chips

Thanks so much for this fellas.

..After some more testing I forgot that I had a similar issue with the return craft. The very center engine wouldn't take the fuel from the tank. I have a reaction wheel in between. So I jumped it and it works. So...the wheel musnt be CFC yet...how is it the other two main engines work? They have the same wheels as the other two in the same spots...

Its not as easy as removing these wheels. I need them there. ( sadly four of them for symmetry. Idk if there torque stacks, but that's not what I did that for ) Doesn't make sense...

Edited August 7, 2013 by Motokid600

[Ziff]

I believe this has to do with how engines draw fuel from tanks. Your two highlighted tanks are both tank #4. That tank has 2 tanks it pulls from on one side, and 3 on the other. This unequal tank balance tends to cause problems. If you were to reverse the fuel flow from tank 3->4 and instead go from 4->3 you would see the exact opposite tanks draw fuel instead. The only fix I know of is to make it so there is an equal number of tanks an engine can draw from on both sides.

[Ziff]

I believe this has to do with how engines draw fuel from tanks. Your two highlighted tanks are both tank #4. That tank has 2 tanks it pulls from on one side, and 3 on the other. This unequal tank balance tends to cause problems. If you were to reverse the fuel flow from tank 3->4 and instead go from 4->3 you would see the exact opposite tanks draw fuel instead. The only fix I know of is to make it so there is an equal number of tanks an engine can draw from on both sides.

[Edit] Wait, you just added that fuel line from 3->4? Weird. Wonder if it has something to do with symmetry placement? Try removing and adding those tanks again.

[Motokid600]

Wait, you just added that fuel line from 3->4? Weird. Wonder if it has something to do with symmetry placement? Try removing and adding those tanks again.

The highlighted tanks? I tried that.. no avail.

Edited August 7, 2013 by Motokid600

[Specialist290]

Have you double-checked to make sure all your fuel lines are set up properly? One set might not be linked up, or you might have placed them using the wrong fuel tank as the source tank.

[Motokid600]

Yea ive gone over it with a fine tooth comb. And...turns out. Ziff you were right. I had tried the just replacing the tanks and that hadn't worked, but I never did try replacing the reaction wheels. THAT worked >.< New problem and I think its as you said earlier.

The circled engines are draining faster then the others. I tried linking the #4 tanks to the center return tank and adding those engines to the firing stage. Nothing. Tried linking them to the out stages of the return craft. ..Nothing. So is there anything I can do to keep tanks 3 and 4 linked? It gives me a nice chunk of extra Dv I could use. I plan on adding probes to a few other moons in the Jool system

Edited August 7, 2013 by Motokid600

[Ziff]

Well now that you have the first part sorted out, remove the fuel line from 3->4 and the #1 tank that is attached to #4 should drain correctly again.

[Motokid600]

Ultimately that's what I did. It works real nice. But I fear im loosing Dv if I dont asparagus stage tanks 3 and 4. Would you say its impossible with this design? I damn near could lol...

[sojourner]

Ultimately that's what I did. It works real nice. But I fear im loosing Dv if I dont asparagus stage tanks 3 and 4. Would you say its impossible with this design? I damn near could lol...

No, now instead of going from 3 to 4 have the 3's and 4's go to the two inner booster tanks which then lead into your central tank. Then you can run all engines on launch for max d/v and still have full tanks when you get down to just the return craft.