Make fuel flow both ways through couplers

[iMAniaC]

I'm sorry if this has been mentioned before (actually, I'd be surprised if it hasn't), but I did a quick search and couldn't find it, so here goes:

Basically, I think it would be nice if both of these designs were working:

This currently works:

This currently doesn't work:

(In case it's hard to see from the screenshots: The design that works has a tank on top with a Tri-Coupler the right way (i.e. the default orientation in the VAB) underneath and three engines connected to the Tri-Coupler. The design that doesn't work has three tanks on top with a Tri-coupler upside down (i.e. flipped and rotated compared the default orientation in the VAB) underneath and one engine connected to the Tri-coupler).

I figure that there's a problem with the fuel only flowing in one direction through the Tri-Coupler. In essence, it would be nice for the fuel to flow both ways Although I haven't tested, I guess this goes for all Couplers and possibly also the Adapters.

[sal_vager]

Sorry but this would require a total rewrite of the craft code and break pretty much everything that's been built before, his is why we have fuel lines as well, and struts as only one of those tanks is attached to that tricoupler.

This has come up before in various guises, it just isn't going to happen.

[vexx32]

This isn't so much making sure fuel flows, as making parts actually link up that way. For now, they don't, and as Sal said, they'd have to redesign the editing spaces and the craft files in order to be able to make it work.

[iMAniaC]

Oh, okay. I was holding off on this suggestion prior to the new version of Unity, but I thought it was worth giving it a shot after the mention of the new Unity version in the ARM patch. I guess I'll have to continue using fuel lines, then

[vexx32]

If you run a search for part attachment or something like that through the forums, you might find one of the older threads that had a huge discussion on it. There were some quality ideas that got tossed around, but for now it seems like recoding the editor isn't too high on Squad's to-do list.

[cantab]

I vaguely recall reading the fuel flow through the tri-couplers was made one way on purpose, to stop issues with uneven fuel drainage. In your second example, if fuel did flow all ways through the tri-couplers and no other changes were made you might find two of the tanks drained fully before the third started emptying, which would really send your rocket off course, and be somewhat counter-intuitive to diagnose.

Of course, it does mean arrangements like this, despite not having the apparent loop issue, won't work either.

(And before anyone asks, no it's not the lander can blocking the flow. Fuel flows through that just fine.)

[Kasuha]

Drawing fuel from the multiside of a coupler was very likely removed on purpose.

In any case, if you need to drain fuel this way, this works:

Edited April 7, 2014 by Kasuha

[KASASpace]

Well, if I recall, the couplers are some sort of an exception to the part hierarchy.

This means it would be tough to code this up.

Although, as Kasuha mentioned, a setup using fuel lines is possible, but it does add more parts, which may be undesirable.