Problem with my lifter.

[Dortmunder]

I've made a bunch of lifters before, usually no problems with them after some tweaking.

The current one I made I can't seem to fix. I have 12 engines attached to fuel tanks around the outside, which tank in to each other(asparagus). But one side seems to be not working properly. They are all mirrors of each other. So the first set of tanks fuel into the second, then the second into the third, the third into a larger set of tanks with a bigger engine.

Problem is, when I decouple the first set of engines, 2 are always still burning fuel. I've looked over it multiple times and redone the fuel lines, but it just keeps doing the same thing.

Is this a bug or what? Anyone else had this problem?

I'll probably post some pictures tomorrow if no one knows what's up. It's getting really annoying

[felixar90]

Better than a picture, post your craft file.

[HoY]

Double post!

[HoY]

Are you dropping 4 at a time or 2?

90% chance it's just a staging setup problem, with 8% chance of fuel line. Just a tiny 2% chance of a bug since its not brought up that often

[Finnerty]

Problem is, when I decouple the first set of engines, 2 are always still burning fuel. I've looked over it multiple times and redone the fuel lines, but it just keeps doing the same thing.

Maybe direction of fuel flow on a couple fuel lines.

[Sorcie]

Sure tease us with something to fix and then don't give pics or file!

[Dortmunder]

Sorry, I posted just before I was going to work

Here's the file, I have the lifter in my payload pack and couldn't find that, so attached it to something and saved that:

http://www./?9r3aehwc4cz126g

Some of the struts and usually 1 or 2 fuel lines come un-attached when loading it, so those may need to be re-done. It's usually the fuel line(s) along the bottom of the outside tanks, and the X struts I have set up.

I looked over it again and tried launching again before posting it. Still couldn't find the problem ><

Edited May 20, 2013 by Dortmunder

[Eleven]

You need to post the mods you're using as well, can't load the craft because I'm missing 9 components.

[Dortmunder]

Oh.

I have a bunch installed. I'll remove the file and add something else to the lifter that doesn't have mods on it. I think all the lifter stuff is stock.

Should work now. It's just attached to an ASAS and stock capsule. http://www./?9r3aehwc4cz126g

Edited May 20, 2013 by Dortmunder

[Eleven]

Oh.

I have a bunch installed. I'll remove the file and add something else to the lifter that doesn't have mods on it. I think all the lifter stuff is stock.

Should work now. It's just attached to an ASAS and stock capsule. http://www./?9r3aehwc4cz126g

Still missing cl.large.nuclearEngine

[EndlessWaves]

the third into a larger set of tanks with a bigger engine.

Are those set of tanks in pairs as well?

In particular if you're feeding several tanks into one and then back out into several KSP will have problems, you just have to redesign in that case.

[superm18]

If you have more than óne fuel line comming from óne fueltank, that's your problem ONLY one fuel line pr. fueltank

[RoboRay]

I think it's the fuel lines.

If you want anything more specific, you're going to have to post some pictures of your ship. We're literally just throwing darts without pictures.

[Dortmunder]

These 3 tanks(mirrored all the way around) feed from right to left. The last one feeds into the large tank they are all attached to. 2 of those large tanks feed into the other 2 large tanks, which in turn feed into the main central tank.

The identical tanks above the outside row feed into the ones below, as I didn't directly attach them to each other, since I attached them to the large tank using a decoupler.

http://imageshack.us/a/img856/8283/screenshot7qd.png

The decouplers are all set up properly, so they are dumping the tanks in proper order. The only problem is, 2 are burning out of fuel faster, which gets repeated each stage. So 4 sets of tanks fall off, 2 of them fall, 2 remain thrusting and fly off, sometimes hitting the main rocket assembly.

http://imageshack.us/a/img842/1516/screenshot8wd.png

Edit: I'm guessing it has something to do with the tanks above that feed directly straight down into the tanks below. Maybe I'll try attaching them directly rather than adding fuel lines to feed downward.

Edited May 21, 2013 by Dortmunder

[RoboRay]

So, the upper tanks in each booster "stack" are actually on their own radial decouplers, which is why you needed the fuel lines going down the "stacks"? You jettison these when they are empty, while the lower tanks are still feeding the engines?

If your lower tanks are not draining at the same rates, you definitely have a problem with the fuel-flow. Probably a loop, somewhere, but it's such a complicated design it's hard to say where.

Simplifying the design with true stacks instead of multiple levels of radial decouplers will make it easier to figure out, if just doing that doesn't fix it for you.

Basically, each engine needs to see a branching tree of fuel tanks it can draw from, with no points in the branches where they reconnect together. If the engine sees two ways to reach the same tank, or if you create a loop where fuel can flow out of a tank then back into the same tank, you confuse the flow-logic and get unpredictable results. It can actually work fine, if you get lucky, but you're much more likely to get tanks draining in the wrong order or at different rates.

Edited May 21, 2013 by RoboRay

[Dortmunder]

I think I got it sorted.

Because I was also using asparagus staging on the 4 large tanks with only 2 feeding into the central tank, the central engine was unbalancing the burn around the outside engines.

So now I just have the central engine disabled until I have staged off the small outside engines and it seems to be working alright.

Now I just have to make sure it doesn't fall apart, which seems to be happening with the payload on top, it gets wobbly once in the higher stages.

Thanks for the help all.

[Nurph]

Managed to fly this to a 100km orbit quite easily.

https://www.dropbox.com/s/y9y2dj18jdurxeo/Med%20Lifter%202.craft?v=0rw--

I added some winglets, set action group 1 to disable the outer mainsails, more launch stabilizers, moar struts where it was needed (connection between center stage and payload was failing, outer mainsails not very well supported), and set up the staging to follow the order that the fuel drains.

Enjoy!

[stupid_chris]

Same here. Your craft had a a lot of unnecessary decouplers, some unnecessary fuel lines and was overstrutted. I removed the excess and fixed your fuel flow. The problem is that all your outer asparagus should've been going into only two of the center mainsail stages, not all the four of them, that is what was creating your fuel excess in some of the external boosters because one of the mainsail was being double fed, reducing the flow, leaving it with more fuel. Also, I added a Rockomax X200-8 to your main engine to prevent it from overheating. Hope I could help ^^

download: http://www./download/cxqj1kn24gt3qk7/MedLifterV2.zip