Fuel Line bug? Or am I just doing it rong?!

[Tiron]

Been trying to build a Returnable Eve expedition for most of a week, and it's not been going well... and now I've run into what I *think* is a bug in the fuel logic, but I'm not sure.

Basically, I'm trying to do inter-stage asparagus-ing (it's awesome when it works), but I'm having some problems getting fuel routed from my lower stages to an upper one(With radial engines) through the lander stage. Basically, the Lander stage is a 3-3-1 asparagus setup (So it can land stably even with one of them gone), and the stages both above and below it are 2-2-2-1 based. The fuel routing just won't seem to work right, no matter what I try.

Instead of burning all the radials on the upper stage off the two active asparagus stages on the bottom, it burns off the two bottom tanks AND off two of the tanks on the lander stage simultaneously(Since the lander's 3-based, this would end up unbalancing it.) Two of the three fuel lines leading from below up to the lander stage show as inactive. Disabling flow on one tank on the lander stage fixes it, but then runs into this bug when you try to re-enable it later.

I made a stripped down mockup (bare minimum of everything, to make it easier to follow and to mess with different configurations: Instead of 2-2-2-1-3-3-1-2-2-2, it's set up as just 2-1-3-1-2 with all the engines but the radials removed for clarity), and it also exhibits the problem. Experimentation has shown that the fuel flow logic can track through either of the transitions by themselves just fine (Meaning the 2-1-2 or the 3-1-2), but can't seem to figure out how to get through both in one go.

I evidentally haven't made enough posts to do attachments, or something, so I can't attach the .craft file. Here's a screenshot of the mockup as a consolation prize: http://steamcommunity.com/sharedfiles/filedetails/?id=101012978

[sal_vager]

Hi Tiron, you can post the link to a mediafire or filedropper page with your craft, or just pastebin it.

I think adding fuel lines makes parts capable of transferring fuel still, maybe that's what is messing up your design?

[Tiron]

Hi Tiron, you can post the link to a mediafire or filedropper page with your craft, or just pastebin it.

I think adding fuel lines makes parts capable of transferring fuel still, maybe that's what is messing up your design?

http://pastebin.com/uYqUwSbk then. Named Fuel Flow Tester.craft

Edit: Sorry, ADHD Got me. I actually thought about that, except that all my lines are purely tank-to-tank, with all of them separated by decouplers... and the problem isn't the fuel flowing where it shouldn't, it's the fuel not flowing. There's actually two fuel lines that are showing up inactive(Grey), even though they're part of a set of three, and the third one is fully functional.

Edit2: Oh, and the tester is set up so that the staging shows the way the fuel should flow, at least in theory, with each fuel line on its own stage so you can see the active and inactive ones easier.

Edited October 5, 2012 by Tiron

[sal_vager]

I tried fuel lines every which way and can't get it to work like you want, I even tried different tank configurations like 4 into 2 into 2.

This has to be a bug, I'd post a bug report here with as much info as you can including this affected craft, then the test team and developers can check it out, and hopefully fix it for 0.17.1, or 0.18 maybe.

[Tiron]

I tried fuel lines every which way and can't get it to work like you want, I even tried different tank configurations like 4 into 2 into 2.

This has to be a bug, I'd post a bug report here with as much info as you can including this affected craft, then the test team and developers can check it out, and hopefully fix it for 0.17.1, or 0.18 maybe.

Yeah, I thought as much but I thought I'd better check first. The thing that gets me is that both of the individual transitions works fine, it's just sequentially that it has a problem with. Thanks, though!

[SpeedDaemon]

What symmetry did you use to add the radial stages? I had a problem with a similar configuration when I added the radials with 6x symmetry on a rocket with 6 2x stages in the outer ring, 3 2x in the inner ring, a central stage. I had to add the fuel lines without symmetry, and the "path" on one side of the rocket worked fine, but the other side did all sorts of weird stuff until I tore it apart and rebuilt with 2x symmetry.

[sjwt]

Two different issues are being encountered here,

The first is for some reason, you have used 2x and 3x symmetry, this confuses the fuel flow algorithm..

The second is that have you noticed stage 10 and 11 the fuel lines are breaking after you start the craft?

I shall assume you have chosen to use the 3x and 2x to get a specific number of fuel tanks in use.. so I have redone the craft in a fashion quickly for you as per this link, I hope it helps..

[Tiron]

Two different issues are being encountered here,

The first is for some reason, you have used 2x and 3x symmetry, this confuses the fuel flow algorithm..

The second is that have you noticed stage 10 and 11 the fuel lines are breaking after you start the craft?

I shall assume you have chosen to use the 3x and 2x to get a specific number of fuel tanks in use.. so I have redone the craft in a fashion quickly for you as per this link, I hope it helps..

The actual rocket that was having the problem had 6-symmetry on all stages, asparagus wired. The upper and lower stages were wired in pairs, the lander stage was wired in triads so that it could land stably. The tester is chopped down, without the 'extra' asparagus stages, to demonstrate the way the fuel flow gets confused. The lines don't break, they just don't get activated. If you move the radial engines down to the tri-stage, all three lines function properly.

I've run the lines both with symmetry enabled and one at a time, and redone the fuel line setup entirely three or four times. And used different wiring schemes to accomplish the task at hand. None of these worked.

The actual rocket is 2m, planned to use 12 tanks (two groups of six in hex symmetry), wrapped around a hex symmetry stage around a single centeral core, all of it asparagus staged. There's multiple stages thrown in, as it's intended for an eve land-and-return trip.

The design I was going for would've have a huge 19-section for on the bottom for kerbin orbit, a small 19 section for transit (outer ring), and landing (middle ring and core) above that, then a large 7-section (inner ring and core only) for Eve ascent, with a 1m 7-section with rad-rockets for final orbital boost and possibly transit, and a small core-only stage on top with a rad-rocket as a contingency. I wire the asparagus setup to cross sections though, so the upper stage engines can fire immediately after the section under them drops, burning fuel from the lower section to do it.

I just can't seem to get it wired through the landing stage.

[sjwt]

If you could post that file, it would help a lot!

[Tiron]

If you could post that file, it would help a lot!

Well it's been modified an aweful lot since I posted, as I try to figure out how to work around the fuel routing problem... I have an idea now that I think will work though... but it's half torn apart atm as I need to do some rebuilding.

It's the exact same problem manifested in the exact same way as on the mockup, though. Complete with the two dead fuel lines and pulling fuel from four tanks instead of two, and two of them on the 3-based landing stage. The mockup's just umpty thousand times easier to follow because it doesn't have 250+ parts. It also doesn't require any mods...unlike the actual rocket.