Fuel Flow Rules (0.24.2)

[Rakaydos]

The Mk 2 Bicoupler allows fuel crossfeed from one "leg" to the other, much to my consternation.

[Padishar]

It certainly shouldn't. Do you have any mods installed that might be messing with this part? Can you check the .cfg file for the part in question and see what the NoCrossFeedNodeKey value is set to? Can you test in a clean 0.25 install? Can you post a (stock) craft file that behaves in this way?

Edited November 26, 2014 by Padishar

[Rakaydos]

Hmm... A simplified test rig gives the expected results... but I'm getting an odd crossfeed on the craft that provoked my post. When the engines of one half are lit, the fuel drains from the expected tanks, AND the tank on the opposite side of the bicoupler.

https://www.dropbox.com/s/9fj28exlv3r3xea/Griffon%20v1.craft?dl=0

It'll be a mess to untangle, I know, but it's better than locking the tank.

[Padishar]

Hmm... A simplified test rig gives the expected results... but I'm getting an odd crossfeed on the craft that provoked my post. When the engines of one half are lit, the fuel drains from the expected tanks, AND the tank on the opposite side of the bicoupler.

https://www.dropbox.com/s/9fj28exlv3r3xea/Griffon%20v1.craft?dl=0

It'll be a mess to untangle, I know, but it's better than locking the tank.

Well, I'm not sure which bit you are actually having trouble with (either the Mk2 bicouplers or the bicoupler at the front that the upper and lower halves are attached to, but you have a serious tangle of fuel lines running between the parts. These are almost certainly providing a path for the fuel to flow from one side of the bicoupler to the other. One thing I notice is that you have a fuel line running from the top of the docking port to the bottom of the size adapter of the top half of the plane and also have fuel lines from the T-800 tanks in the top half back to the docking port in the bottom half.

[Rakaydos]

Fuel drain is supposed to go- Bottom flank tanks (symmetric), Top flank tanks (Symmetric), bottom core tank (symmetric, draining inward toward the dockig port) and finally the top core tanks, draining front to back.

With the Mk2 Bicoupler eliminted, my next guess is that the radial attachment of the top flank tank is draining fuel from the top core- specificallly, whichever side hasnt already been "checked" by that engine, which is why I confused the problem with the Mk 2 Bi coupler.

[basic.syntax]

Just wanted to relate my space plane experience with .90 before reading these last two pages, that, you can have beautiful symmetric flameouts... far to early... if engines are placed in symmetry, but intakes are [alt]-copied. (Full agreement with AlexanderB. And thanks to Kasuha for a great thread and pix making things clear.)

I had much better results with the annoying, tedious process of alternate careful placing of intake/engine, intake/engine - all 'new' parts, for 14 engines. (140 ton fuel lifter.) Several times I was thinking "rockets are far easier to work with, why am I still messing with this..." then I arrived here and started to make progress

I hope that Squad may come up with a fix that changes how these types of parts are evaluated and sequenced, behind the scenes.

[zekes]

strange physics is at work here....

[John FX]

I'm not sure these will get updated for 0.90.0 or 1.0, if there are any changes to fuel flow, Kasuha has not posted since oct 2014

They may have moved on to other pastures...

Edited March 20, 2015 by John FX

[AlexanderB]

I'm going to assume not much has changed, but we can run some of the experiments to find out.

using alt-click to copy intakes does something weird to them, yes.

[Red Iron Crown]

Intake Build Aid is useful for determining where intakes and engines fall in the part order if someone wants to run some experiments with the alt-click placement.