Fuel problems.

[glen.mack]

I am having a headache. I can't figure out how to do this so all the fuel is used by all of the engines. Any ideas?

With no fuel lines, each of the side engines use the fuel in the standard fueselage, and the inline engines use the fuel going from front to back, I believe. (This is however not the case, see below)

This is not balance related, it works fine no matter the order the tanks is drained. I just can't get the oxidiser to be distributed when switching to it. The bottom engines flame out "no oxidiser"

Let me know if I need to upload the craft file.

Edited February 27, 2015 by glen.mack

[SkyRender]

Wow, that is one absurdly complex-looking craft... You might just want to get the TAC Fuel Balancer mod and not have to hassle with figuring out the logistics of the fuel lines. Because trust me, those logistics will be a nightmare with a configuration like that.

[r_rolo1]

The best solution for that would be all the engines drinking directly from just one tank and all the other tanks being connected to that one. But given the design of your vessel, that might just short of impossible ...

That said, you can find a detailed look on the fuel flow rules in the tutorials section ( I'm not sure if it is up to date, given that there were some changes in the fuel lines code in 0.90, but i belive that it is basically still correct ).

[zarakon]

Fuel lines from the outer parts to the middle parts

Fuel lines from the middle parts to the outer engines

I don't know why you have a fuel line going between the two halves. That seems unnecessary if they are equivalent

[glen.mack]

The best solution for that would be all the engines drinking directly from just one tank and all the other tanks being connected to that one. But given the design of your vessel, that might just short of impossible ...

That said, you can find a detailed look on the fuel flow rules in the tutorials section ( I'm not sure if it is up to date, given that there were some changes in the fuel lines code in 0.90, but i belive that it is basically still correct ).

This works, but kind of spoils the design, lol. It's just a mess of yellow at the back.

- - - Updated - - -

Fuel lines from the outer parts to the middle parts

Fuel lines from the middle parts to the outer engines

I don't know why you have a fuel line going between the two halves. That seems unnecessary if they are equivalent

They are not equivalent, I don't know how, but they aren't. My right click function works badly and I can't keep track of oxidser in flight.

[thadisjones]

What is that I don't even.

I mean it's definitely one of the weirdest things I've seen and if you can get it into orbit more credit to you.

But seriously I'm not surprised you've got problems with whatever that's supposed to be. From looking at your design the top and bottom look like they are equal in fuel/ox capacity. Perhaps the problem is that your upper RAPIERS and intakes are a dozen meters higher altitude than the bottom ones, thus they run at different ISP's and maybe even auto-switch to closed mode earlier? I'm not sure if IntakeAir would be shared automatically between the upper and lower halves and honestly I can't decide if that would be better or worse.

[Landge]

That looks challenging. There are a few designs I've had where I had to add fuel lines in both directions for dual flow. Not sure that would work in your case though.

It's times like this where I wish fuel lines could be toggled for forward or bi-directional flow. Heck even have it work like RCS. I wonder if somebody already made a mod for that?

[glen.mack]

What is that I don't even.

I mean it's definitely one of the weirdest things I've seen and if you can get it into orbit more credit to you.

But seriously I'm not surprised you've got problems with whatever that's supposed to be. From looking at your design the top and bottom look like they are equal in fuel/ox capacity. Perhaps the problem is that your upper RAPIERS and intakes are a dozen meters higher altitude than the bottom ones, thus they run at different ISP's and maybe even auto-switch to closed mode earlier? I'm not sure if IntakeAir would be shared automatically between the upper and lower halves and honestly I can't decide if that would be better or worse.

Yeah, everything is pretty complicated. I can get into space then blast the payload into a stable orbit, but then I lose everything on the way down.

That looks challenging. There are a few designs I've had where I had to add fuel lines in both directions for dual flow. Not sure that would work in your case though.

It's times like this where I wish fuel lines could be toggled for forward or bi-directional flow. Heck even have it work like RCS. I wonder if somebody already made a mod for that?

I think I've sorted the fuel flow, just need to sort all the other problems out, lol/

[bonyetty]

Some parts do not transfer fuel like the structural plates. Parts such as these can be used to isolate tanks from other tanks, engines or any other part and widgets used to hide them. The cubic octag part can be used as a funnel(multiple fuel lines into one) or splitter (one fuel line into many). By placing a cubic on a plate and using the widget to put the cubic through the plate fuel can also flow through parts without cross feeding. Hopefully this may help.

Edited February 28, 2015 by bonyetty

[glen.mack]

Some parts do not transfer fuel like the structural plates. Parts such as these can be used to isolate tanks from other tanks, engines or any other and widgets used to hide them. The cubic octag part can be used as a funnel(multiple fuel lines into one) or splitter (one fuel line into many). By placing a cubic on a plate and using the widget to put the cubic through the plate fuel can also flow through parts without cross feeding. Hopefully this may help.

This is incredibly useful to know as I go into the 7th iteration of this craft! Thank you!

[bonyetty]

You are most welcome although I can't take credit for working this out. EJ_SA is an amazing KSP twitch streamer with very impressive KSP building skills. Definitely worth checking out for building tips.

[Redshift OTF]

I assume the top and bottom pieces can have their own independent fuel supplies so no need to connect them. To get the inline and side engines to use/have available all the fuel in their sections connect a fuel line from the outer fuselage, (I'm assuming there's liquid fuel in them), to the inline fuselage and then connect another fuel line from the inline fuselage directly to the side engines. Apologies if you already knew this.

[cantab]

Yeah, I suggest ensuring that the upper and lower fuselages have no fuel transfer between them. Various parts are marked as no fuel crossfeed.

Be aware that radial decouplers are not no crossfeed parts. Rather, special coding prevents fuel crossfeed if a fuel tank is attached to them. If some other part is attached to them fuel will flow. This test rig demonstrates the behaviour: https://flic.kr/p/qYvM8m (Structural fuselage, with no fuel capacity, on the right.)

[Vanamonde]

This question about how to play the game has been moved to Gameplay Questions.