What the heck happened to fuel routing rules?

[ajburges]

Can anyone explain what is going on with the fuel routing rules? The initial liquid stage is somehow getting fuel from the final stage when the fuel ducts are added. Do radial separators allow cross-feed now?

Edited June 3, 2015 by ajburges

[Starwhip]

They do, yes.

I thought you were going to ask why the SRB wasn't feeding into the center stack or something.

[Tex]

Apparently they do, but I've never had a situation like that occur. Those fuel lines are pointless, SRBs and liquid-fuel engines, by definition, use different fuels. Take them off and problem solved

[Leszek]

Apparently they do, but I've never had a situation like that occur. Those fuel lines are pointless, SRBs and liquid-fuel engines, by definition, use different fuels. Take them off and problem solved

Except that he ins't using the SRB's fuel, the SRB's are acting as a fuel line for FLO from above.

[Starwhip]

Except that he ins't using the SRB's fuel, the SRB's are acting as a fuel line for FLO from above.

Yep. Don't know why ajburges did so, but this is definitely the case.

[Laie]

It has been thus at least since 0.23.5: radial decouplers allow crossfeed if the part that is attached to them does not provide the resource in question. There's very few useful applications and only rarely does one stumble across it by accident like you did, so it's not exactly a well-known fact.

[Padishar]

Can anyone explain what is going on with the fuel routing rules? The initial liquid stage is somehow getting fuel from the final stage when the fuel ducts are added. Do radial separators allow cross-feed now?

This thread explains the details of the fuel flow rules. It hasn't been updated in quite a while but the only thing I am aware of that is different in 1.0 is that engines can override the flow mode for each of the resources they use (jet engines do this in 1.0 to make the fuel draw like monopropellant rather than liquid fuel).

As Laie said, radial decouplers have allowed crossfeed since at least 0.23.5 and almost certainly earlier.

[ajburges]

It's not apparent in the picture, but the SRBs are topped with small LFO cans. Zoomed in too much to make the connections more apparent.

[cybersol]

So why not attached the SRBs to the lower stage? It should not only fix your problems, but also save the decoupler weight on your top stage.

[Wanderfound]

It's not apparent in the picture, but the SRBs are topped with small LFO cans. Zoomed in too much to make the connections more apparent.

Which is a very useful trick, BTW. Almost any time that I'm using radial SRBs, they'll each have a small fuel can on the nose to feed the core. If you're taking the extra drag of the radial boosters, you may as well make the most of it.

[Tex]

Which is a very useful trick, BTW.

Hmm.... I might just try and use that trick from now on. Thanks a million, y'all!

[tg626]

Meanwhile tweak able everything adds a button to the right click menu to shutoff the crossfeed.

[ajburges]

Apologizes for the necro but figured I should update status to answered.

Off topic. I wound up ditching the design. Finding out that an FL-T800 and a LV-T30 gives better dV and comparable trust to a Kickback for less funds has killed the viability of large SRBs for me. Now I just stack Fleas for a launch TWR of 6+ to get to high subsonic (250 m/s) faster, then linger there until terminal velocity is over 500 m/s before breaking the mach barrier. Current design is focused on a higher dV last stage on a 909. However, I've unlocked nukes and turbojets. Now I'm transitioning to nuclear tugs, space planes, and ultra-efficient vacuum rescue pods.