Problems with asparagus staging/parallel staging

[JStevenson]

Hi folks,

I'm currently having problems setting up asparagus staging for big boosters ( for heavy lifting off Kerbin). I'm running the most recent version of KSP in Career mode.

I've carefully setup to pairs of boosters around a large central core ( core is the huge four engine cluster with two large ranks above. Each booster is one if those twin engines with orange large tank an cone.   I'm  using a single large hydraulic decoupler roughly at the mass center of the boosters.

I set up the asparagus staging using those yellow ducts to plumb from Paul 1 to pair 2 then into the core tanks.   And setup the decoupler staging to shed the booster pairs in the same order. 

But test flights so far gave been less than successful. The problems I get are:

1) not getting sequential high burn rate on outer tanks first. All booster and the central core appear to be burning all if the lower stage fuel as a single burn. 

2) attempts to stage each pair of decoupler results in an explosion and no shedding of the boosters! It's almost like these hydraulic decoupled aren't releasing ( or booster stage is otherwise permanently glued together) 

I suspect problem 1 is a symptom or the decoupling problem 2?

Has anyone using the more recent KSP also had these problems (and/or have solved them)?

Again I've noticed most online KSP tutorials are quite old (2012-2013) and make,asparagus,staging look easy. Is this another case where something has changed in more recent versions that has rendered this method more difficult? 

Am I simply using the wrong decoupler?!

Thanks in advance, 

Jon

Sorry for the terrible grammar!   I typed my question on my cellphone with one thumb injured so auto complete made a mess of some sentences! If meanings are unclear I'll try to clarify tonight when I get back to my real PC! 

[Geonovast]

I've had a lot of problems with the fuel lines working correctly using the Twin Boar engines.  They always seem to ignore the lines and drain evenly.

Check to make sure you have crossfeed disabled on the decouplers, then maybe try using a different engine on the boosters.

As far as the kerploding, I'm not sure.  Can you share some screenshots, and possibly the craft file?

[Kryxal]

If the decouplers aren't working, you may have attached the tanks directly to the center stack.  That sort of thing is sort of hard to see with the lower-profile decouplers at times.  This might also lead to everything being considered connected instead of using the fuel ducts, regardless of crossfeed settings.  Try using the TT-70 for a test design, those are blatantly obvious when you miss mounting on them ... come to think of it, with the 2.5m tanks on the outside you probably want the spacing of those decouplers anyway.

Edited October 27, 2017 by Kryxal
typo

[ShootNoChutes]

Also separators may help with decoupling, and maybe check the flow priority of the tanks, I'm new at this but it might be worth checking out.

[JStevenson]

Thanks for the suggestions. I'll try these out tonight and back to you with the results. Is there a special trick to attaching things like the craft file ( or even screenshots) in this forum. I tried do this several weeks ago on another matter but never did get pictures to attach properly!

[Vanamonde]

1) Are the tanks actually running out of fuel in the wrong order? Because the bar-graph displays in-flight are misleading, and their relative fullnesses come out looking wrong. 

2) The most common reason for this is that you may have accidentally attached the boosters directly to the core stack rather than to the decouplers. Is there a visible gap between them? 

Pictures of your craft often help in diagnosing problems. Maybe post a few of those? 

[bewing]

1 hour ago, JStevenson said:

Thanks for the suggestions. I'll try these out tonight and back to you with the results. Is there a special trick to attaching things like the craft file ( or even screenshots) in this forum. I tried do this several weeks ago on another matter but never did get pictures to attach properly!

You can't attach directly to the forum. You need to use a file/image server. For craft files and savegames, places like dropbox, google drive, or pastebin work (with appropriate settings). For images, imgur is a good choice. You have to upload the image to the website, then it gives you a URL to share. Embedding images is even a bit more complicated than that.

 

[Spricigo]

1.In the editor, hovering the mouse over a part should highlight the part and any part attached to it. Use this to check if the boosters are correctly attached to decloupes (from the description of the issue seems it is not)

2.If the forces acting upon the booster at the separation is resulting in torque the booster will rotate and may collide with your craft. Try to place the decouple right at the CoM of the empty booster or a little higher (you probably will move ahead of the boosters before the bottom side reach the rocket) and consider using aerodynamic forces or separators to push the boostets away faster.

3.(the question you didn't asked) You may setup asparagus stagging using fuel priority and cross feed. Both options require [allow advanced tweakables] enabled pn settings. Notice that cross feed work both ways on decouplers, so you need to watch the fuel tanks to see  when they dry out.

9 hours ago, JStevenson said:

Again I've noticed most online KSP tutorials are quite old (2012-2013) and make,asparagus,staging look easy. Is this another case where something has changed in more recent versions that has rendered this method more difficult?

No. In fact there is now a new method with advamced tweakables. However, due to changes to the game, asparagus is not as much an advantage as it used to be in older versions.

[JStevenson]

Thanks for the very detailed help and ideas.   With all your help I was able to adjust my Jupiter 6 heavy booster to work properly.   The problem was the use of those radial hydraulic separators with the larger fuel tanks and the " boar" twin engines as the boosters. Seems the boosters were permanently attached even though I was careful to move them out radially to leave a gap. Visually it looked right but obviously the simulation still considered them attached. Switching to the TT-70s (2 for each) worked well and,also made for very clean separations in most cases.   A possible future tweak will be to add small retro jets to push the boosters away at separation to be more safe.  

Anyways, now that the boosters are indeed separate from the core I was able to set up asparagus staging properly.

Thanks to all that replied for your excellent suggestions.

Happy flying!

Jon

[Spricigo]

1 hour ago, JStevenson said:

Switching to the TT-70s (2 for each) worked well

Each part can have only one parent. That means that half of your decouplers are not attached to the boosters and are just adding mass, drag and something to your boosters to collide with after separation. Fortunately it's not causing serious issues, but is still hindering you.