Why rocket not listen to fuel lines...

[fireblade274]

Ive been up for 4 hours getting this tug into space. It's 5 am now and im going to bed

For some reason when im at my final stages (atomic rockets are all thats left) the ship is drawing fuel from all 4 bottom mk2 containers, when I have fuel lines set to have it draw from only 2 that are diagonal from each other.

Fuel drawing from all 4 bottom tanks (i could only show proof of 2 in pic but it draws from all 4): https://www.dropbox.com/s/41365b7qi100c97/2015-09-12_00005.jpg?dl=0

detailed lit up view of connections in VAB: https://www.dropbox.com/s/oofsztejnauu85j/2015-09-12_00006.jpg?dl=0

WHY

Here is the craft if you want: https://www.dropbox.com/s/kob0wvulslhsm2n/t%20LR.craft?dl=0

If you can get it into stable orbit before engaging atomic engines, in the most economical way money wise, you get brownie points. But I really just want the fuel to work.

Edited September 12, 2015 by fireblade274

[Padishar]

You are almost certainly misunderstanding how the fuel flow works because it is quite complex and not particularly intuitive. I'll try to take a look at your craft later today if no one else has but, in the meantime, this thread describes the mechanism in detail (though note that jet engines and the rapier in LF+O mode all drain fuel using the MonoProp/Xenon flow mode rather than the normal rocket one).

[tbarcello]

That's not "top" tank from the games perspective. There is no "top" tank, actually, only closest to engine and farest. Farest is the bottom one. Top one is full, so no fuel will go there.

- - - Updated - - -

This is schematic view of your fuel flow by me.

Black is ur engines.

Black B is bottom tanks.

Pink tanks are the ones you wanna ditch first.

Green are last.

Yellow are your fuel lines

Blue is ur central tank.

Light blue are my ammendments.

The waves are tanks, that draining. The crossed wave shows, that this tank is not drained, because replentished.

[The_Rocketeer]

That's a really baffling diagram... it's not wrong, it's just a bit confusing!

Like tbarcello says, fuel drains towards the engine from the furthest tank. In other words, the tank that has the most steps between it and the engine will drain first. A step could be an ordinary node connection between two tanks, or it could be a hose. It's also helpful to count the first step as the join between the engine and the first tank. If two tanks are an equal number of steps away, they'll drain at the same rate.

Relating to the diagram, we'll ignore the blue arrows for now, so assume the yellow arrows are hoses. The top right box on the pink stack is 8 steps from the engine - the furthest. Once it drains, the one below it drains - 7 steps. Next the one below that, 6 steps, and now the pink stack is empty. Next, both ends of the green row drain into the middle, because they're both 5 steps from the tank. Once they're empty, the middle tank is 4 steps, BUT so is the blue tank at the top, so they drain together. Then both the blue and green sections are empty, so next the red stack drains from top to bottom.

Using the blue arrows as hoses, the bottom tank of the pink would drain first (7 steps), then the one above it would drain at the same time as the left-most of the green row (6 steps) the top pink and middle green (5 steps), then right hand green (4 steps) then the red stack again from top to bottom, leaving the blue tank full (because it's not connected).

I hope that's helpful.

[Red Iron Crown]

"Furthest tank" is not a good way to put it. Imagine you have a stack of five tanks over an engine, and then attach to a radial tank to the lowest tank and connect it to the core with a fuel line. Which tank will drain first? How many steps to that tank?

[fireblade274]

I fixed it, I just had to place the fuel lines from the bottom tanks, not the top. Thanks guys!

[The_Rocketeer]

"Furthest tank" is not a good way to put it. Imagine you have a stack of five tanks over an engine, and then attach to a radial tank to the lowest tank and connect it to the core with a fuel line. Which tank will drain first? How many steps to that tank?

It depends which tank the hose from the radial tank was connected to in the core stack.

Both 'furthest' and 'top' are problematic words, but thinking of the number of steps between tanks it makes more sense to speak of it as a distance than a height (especially when dealing with a rocket in orbit/lying flat/a space plane).

[Red Iron Crown]

It does not depend on which tank it's connected to, the radial tank connected by a fuel line will *always* drain first. I was considering "furthest" as in steps, not physical distance.

[The_Rocketeer]

It does not depend on which tank it's connected to, the radial tank connected by a fuel line will *always* drain first. I was considering "furthest" as in steps, not physical distance.

If that's so I've been labouring under false pretenses! I shall have to experiment...

If so, the fuel hoses add a secondary hierarchy then, dividing the stacks of steps into separate 'flights'.

Nonetheless, my description of the yellow system in the diagram was accurate, since the issue you've highlighted doesn't arise until the blue system is used.

[Padishar]

Basically fuel lines ending at a part are scanned first and only if none of them provide any fuel does the scan go on to axially attached parts, a surface attached parent or the part itself. The full mechanism is described in detail in the thread I linked in post #2 above...

[tbarcello]

That's a really baffling diagram... it's not wrong, it's just a bit confusing!

Sorry 'bout that.

I'm surprised anyone could understand that. I wouldn't. That's just the best I could do under circumstances, but really wanted to help, even in my situation.