How do i... Reverse fuel flow?

[Braun]

I managed to come up with a way to get rid of emptied tanks, but since I need to clear them from the bottom up that way, I don\'t know what to do. I tried connecting them with fuel tubes, but anything short of horizontaly daisy chaining the tanks fails.

[Kosmo-not]

I managed to come up with a way to get rid of emptied tanks, but since I need to clear them from the bottom up that way, I don\'t know what to do. I tried connecting them with fuel tubes, but anything short of horizontaly daisy chaining the tanks fails.

The problem lies in that the stack decouplers have fuel crossflow enabled. You need to put something in the way to disrupt that fuel flow.

[zack2014]

| | | |

|fuel| <- | |

| __| | __ |

^

| | |

| |

| |

Arrows are fuel lines

[Zephram Kerman]

The problem lies in that the stack decouplers have fuel crossflow enabled. You need to put something in the way to disrupt that fuel flow.

Make a copy of the stack decoupler part folder, and then edit the .cfg file to disable fuel crossflow.

[Braun]

Yes,

|   |   |   |
|fuel| <- |   |
| __|   | __ |
         ^
       |  |  |
       |    |
       |    |

Arrows are fuel lines

I did that, but since I also have done

Make a copy of the stack decoupler part folder, and then edit the .cfg file to disable fuel crossflow.

before posting this thread, I can say: Fuel lines attach to the decoupler instead to the above tank.

Additionaly, instead of draining the first tank in the daisy chain, the system empties the first attached and takes from the tanks below them only after those first ones are empty.

[Zephram Kerman]

Fuel lines attach to the decoupler instead to the above tank.

I\'ve noticed when attaching fuel lines, the connector will jump to any part that gets in the way. Since the decouplers are a bit wider than the fuel tanks, this might be the problem. Can you connect the tanks diagonally, to get the hoses clear of the decouplers?

[hubbazoot]

I\'ve tried doing what you\'re trying to do by adding an intermediary tank. Even using a fuel line to route the fuel back up, the bottom tank still drained first.

If you attach the tanks directly side to side, no fuel will flow between them. This is probably the simplest way to allow for precise fuel control.

[Braun]

Can you connect the tanks diagonally, to get the hoses clear of the decouplers?

that\'s what I did.

If you attach the tanks directly side to side, no fuel will flow between them. This is probably the simplest way to allow for precise fuel contro

Then I can\'t dispose them and the whole operation is lead ad absurdum.

My problem here is...

 --------
 | Tank1 |
 |    ----------->Engine
 |  ^  |
 |  |  |
 ----|---
(  |  )
 ----|---
 |  |  |
 |    |
 |    |
 | Tank2 |
 --------
(     )
 --------

...the top tanks drain before the lower ones.

Of course that\'s physical correct, but with all the irregularitys here...

I\'d wish we would have fuel lines that only open when activated!

[Temstar]

Don\'t fight the fuel flow, use it to work for you:

See here I have the two lower side tanks connected to upper center tank. At liftoff I fire all three engines and fuel starts to drain from each stack. However the upper center tank is constantly being topped off by fuel feed from the two lower side tanks which in effect means the three engines are draining the 4 side tanks in between them. When the two side stacks run out of fuel I stage stage 4 which blows off the side stacks leaving me with a center engine still firing and two full tanks of fuel still.

Unfortunately if you are planning to drop only empty fuel tanks and do so one at a time the only way to do it is horizontally. The point is though it\'s kind of a waste since as your rocket lighten you should be dropping engines along with tanks. If your rocket isn\'t doing that then it means either you will have too many engines later into the flight or not enough at lift off.

[Zephram Kerman]

...When the two side stacks run out of fuel I stage stage 4 which blows off the side stacks leaving me with a center engine still firing and two full tanks of fuel still.

This is my favorite configuration! Having all engines running at launch really helps with efficiency. Basically, they are liquid boosters attached radially.

Unfortunately if you are planning to drop only empty fuel tanks and do so one at a time the only way to do it is horizontally. The point is though it\'s kind of a waste since as your rocket lighten you should be dropping engines along with tanks. If your rocket isn\'t doing that then it means either you will have too many engines later into the flight or not enough at lift off.

I think it may be ok to have extra engines for a little while. Above 12km, most KSP rockets can\'t keep up with terminal velocity anyway. But if all the original engines are still running with only 1/3 the fuel, that\'s quite a powerful craft. Certain maneuvers are most efficient if done in a short burst.

Because of this, I\'ve been trying to work out a way to keep the engines but stage the empty tanks.

[hubbazoot]

This is my favorite configuration! Having all engines running at launch really helps with efficiency. Basically, they are liquid boosters attached radially.

I think it may be ok to have extra engines for a little while. Above 12km, most KSP rockets can\'t keep up with terminal velocity anyway. But if all the original engines are still running with only 1/3 the fuel, that\'s quite a powerful craft. Certain maneuvers are most efficient if done in a short burst.

Because of this, I\'ve been trying to work out a way to keep the engines but stage the empty tanks.

As of 14.4, You can route fuel lines directly to engines.

And I made you a present. It\'ll make it into a low kerbin orbit.

It\'s far from...elegant, but it works.

[Zephram Kerman]

Heyyyy, thanks Hubbazoot! That was very nice.

I took your example, and made something similar. (Call it a reciprocal gift.) It gets to Mun and back with just 19 tanks. It\'s very quick off the launch pad and in the ascent, so it helps to keep the speed below terminal velocity. If all goes well, the drop tanks go in Booster Bay, the first three engines dissolve in the atmosphere during circularization, and the second three engines hit the Mun during descent. The final engine is the only gimballed one, and has a single fuel tank for landing and return. We returned to Kerbin with almost half a tank in reserve, which is nice if you want to control the landing site. Or if you want to add weird things like lander legs.