ISRU + Aluminum Hybrid Rockets Require Incorrectly Facing Fuel Lines

[fandingo]

The arrows on fuel lines are supposed to indicate which direction resources flow from. At least with the ISRU refinery and AlO3 rockets, the fuel lines must be placed backwards.

Perhaps there is some limitation in KSP that requires this counterintuitive behavior, but it's not documented on the wiki. Counterintuitive behavior absolutely needs to be documented.

[Rebelgamer]

It's listed in the FAQ on the wiki:

I have a refinery on the Mun and I'm trying to refuel my Aluminium Hybrid Rocket but I'm not getting any Oxidiser, why is this?

Oxidiser requires fuel crossfeed capable components or fuel lines in order to be transferred between parts. Fuel lines from refineries need to go in the opposite direction to what you expect - i.e. from the hybrid rocket to the refinery.

It probably wouldn't hurt to add this note to the page for the Aluminium Hybrid Rocket though.

[fandingo]

It needs to be on the primary documentation for both the ISRU refinery and Aluminium Hybrid pages. When I built my ship, I reread the microwave rx, alumiuminum hybrid, and ISRU pages through several times to make sure I understood all components completely. I get to the mun, and oops, ship ain't gonna work. The FAQ simply isn't the place for this sort of information.

Additionally, why on earth are the fuel lines used like this? It makes absolutely zero sense given the logic in the rest of the game.

The way the fuel lines are used is a bug, and also the way that it's documented is a bug.

[Rebelgamer]

I just use Cross-feed Enabler and TAC Fuel Balancer, as long as their on the same craft, you can move it around. I agree though that the fuel lines need some work, if fuel can move one direction, why not in both, or allow direction to be set during the design phase.

If you KAS installed you can add a fuel line but that would require sending a second flight to meet up with the first, or edit your savefile to change the direction of flow on the fuel line.