Fuel draining from final stage first

[zcar.300]

Is there no way to attach the craft file?

Anyway, there are no fuel lines except for the ones going to the nuclear engines. But when I launch all 16 of the lifter engine pull from the top orange tank first. I haven't had this problem with other designs so I'm at a lose.

Edited September 12, 2013 by zcar.300

[capi3101]

Fuel does flow through girders and BZ-52s, believe it or not.

...except you've also got radial decouplers there, don't you?

Have you tried tying the decouplers to an action group to disable crossfeed? Crossfeed should be disabled by default, but maybe something odd is going on in this case.

Another possibility is that the game thinks your girders are directly attached to the orange tank and not the decoupler. Crack open your craft file, find the girders involved and see what they have as their root part. If they don't say anything about a decoupler, that's what's going on.

Edited September 12, 2013 by capi3101

[zcar.300]

I do have Radial decouplers. I have never set anything up in the action groups but I'll take a stab at it. I've used girders and BZ-52s before without a problem. So maybe it is the addition of the decouplers that throws it off.

I believe this is the part in the craft file. But I'm not real sure what I'm looking at here.

PART
{
	part = trussPiece1x_4294748808
	partName = Part
	pos = -1.691101,16.651,-1.691099
	rot = -0.270598,0.6532815,-0.6532815,-0.2705981
	attRot = 0,0,0,1
	mir = 1,1,1
	istg = 2
	dstg = 2
	sidx = -1
	sqor = -1
	attm = 1
	link = strutConnector_4294748728
	link = stackPoint1_4294747576
	link = strutConnector_4294747336
	sym = trussPiece1x_4294748788
	sym = trussPiece1x_4294748768
	sym = trussPiece1x_4294748748
	srfN = srfAttach,radialDecoupler2_4294748984
	EVENTS
	{
	}
	ACTIONS
	{
	} 

[Evrion]

Given the decouplers, as mentioned, it shouldn't happen. I know I have that problem when I attach a tug to a lander craft, then the tug draws fuel from the lander. But that's through a docking port.

Looking at your design, I think you could actually just attach the lower orange tanks to the radial decouplers directly. Unless there is something I'm missing. This might fix the problem.

[zcar.300]

I can't figure out how to make the action group turn off the fuel crossfeed. I can make them decouple with the action group.

The reason I don't have them directly connected to the decouplers is because then the tanks clip into the upper stage.

... I take that back. I did that because I couldn't get the tanks to mount near the top. they always want to attach near the center of the tank.

Edited September 12, 2013 by zcar.300

[stupid_chris]

The decouplers do allow fuel crossfeed. The way you build your craft makes fuel flow to the engines in the bottom. Basically, the current tree structure of the editor makes it so that all those boosters below are considered in the same stack as the orange tank above, reason why it drains the fuel from there. You can either rebuild your craft and attach the tanks directly to the decouplers, or disable the fuel flow in the big orange tank manually before lifting off. Both should solve your problem.

[zcar.300]

Chris -

So if I mount the tanks directly to the decouplers it doesn't consider them in the same stack? But if you have anything between the decouplers and the tank it does?

[stupid_chris]

No it's not a matter of having something between, it's how you mounted them. It's a matter of attachment nodes. Basically, by placing your trusses this way, you "extend" the stack. Then the radial connector also extends the stack down to the boosters below. If you would've attached the trusses radially (by that I mean the green attachment node pointing up, not towards the decoupler), this wouldn't be happening. For the game to consider something as a new stack, it needs to be attached radially. If you connect things by their heads where there is a node, you create a fuel flow weirdness like this. The easiest if you want to keep your design would be to cut fuel flow in the top orange tank as I said, but changing your design shouldn't be too hard.

[zcar.300]

Ahh OK. That makes sense in a round about way. Thank you.

I will mark the thread answered. If I can figure out how.

Edited September 12, 2013 by zcar.300

[stupid_chris]

Take a look at the Forum FAQ, you'll find the answer you're looking for there along with many other questions you might have