Is there a way to 'kick' stages off my rocket?

[Tassyr]

The title. Basically, I'll have four or so liquid fuel engines arranged around a central rocket, complete with fuel tanks. If I don't deploy them juuuuuuust right, the entire thing crashes into itself. I've used struts, I've used couplers, I've even tried using a retrorocket mod. But all careen into my ship somehow. Is there some trick to side-stage separation I'm just not seeing here?

[Clouds]

Well, I can make some suggestions. Dunno if they'll be any different than what you're doing already:

Decouplers apply a small separation force when triggered, so where they are relative to the center of mass of the jettisoned parts will matter. Generally, having it forward of the center of mass works better, so they spin more open at the front, letting the remaining ship pass through. If the decoupler is more rearward, the jettisoned parts will spin more closed at the front.

Don't eject engines that are still burning unless you've planned it carefully. If there's fuel left, turn throttle to 0 for a moment. Even better is if the jettisoned parts are not thrusting and the center ship is, so it will clear the debris rapidly.

If all else fails, maneuver into a rather speedy roll before triggering the decouplers, so radial debris will be flung away like water drops off a fan.

[SciMan]

i've had problems decoupling radial stages before as well, my personal solution is to edit the .cfg of the radial decoupler. and its hardly what one would call a "hack" type edit, there's only one line of code to change, and it actually makes it work like (i think) the dev's intended it to.

so, the line you want to change looks like this

 
// --- Stage Separator parameters ---

ejectionForce = (number here)

and for the tt-38k radial decoupler i think i used a value of about 250 for a reliable "shove" away from your rocket, you can try using a smaller or larger number (bigger number = bigger push), but try to keep it under 1000, else you might find the spent stage isn't the only thing that gets flung off your rocket!

Edited August 30, 2012 by SciMan
clarification

[trbinsc]

In the new update, 0.17, there will be separation motors (the tiny SRBs) to push away discarded stages.

[Markus Reese]

There is another way you can do it that use. First off note that this is really mostly for more in space just due to trying to control the rocket. If it is in atmosphere, you can try the following ideas as well, but less effective.

First is to position your radial decouplers around the more towards the top. Have them hang a bit below the inner stage they are connected to. Usually this will "Kick" the top out. The lower portions will swing in a bit, but provided they are hanging past, and you are providing thrust when they disengage, it should kick them clear.

Second task, and my prefered one since hopefully you can get out of atmosphere with your main boosters is to cut your engines. Be sure no SAS is going, and just spin your rocket. The gyroscopic effect will fling your stages smoothly clear, and then just re-apply thrust and coast clear. It is doable in atmosphere too, but is easier to lose rocket control. That being said, I have in other rocket building days, used the radial mount engines on an angle or SRBs to start my rocket spinning just before I would need to jettison the stage. The angled thrust if placed in the right spot will spin the rocket regardless of there being an ASAS. Engage, get spin started, jettison when fuel is out and ASAS hopefully can keep you going the right direction.

[Vanamonde]

I was having that problem for a while. I don't know what your ship looks like, but for me the solution was to arrange the ejected stage so that the center of mass of each piece is slightly outboard. That way, when you eject it the pieces start rotating around that COG, opening like a banana-peel, and leaving a gap for the rest of the ship to pass through.

[zapy97]

what i do since most of my staging is in the atmosphere is just to put winglets on them which makes them go outward or i just make them explode while outside the atmosphere so i dont have to worry about them cuasing lag, the small parachute is good when placed near the top on the outside of the "stage" so it gets pulled away when at max thrust.

[Nibb31]

There are small retrorockets in some mod packs. You can put them at a 90° angle so that your radial stages are pushed away.

You can also increase dramatically the EjectionForce variable in the CFG files of the decouplers. I tend to set the value to something like 2500.

[RyanGt04]

I use a radial fuel tank design on most of my rockets also. Like others have said, position the decouplers near the top of the so that is pushed out enough for your center stage to clear. If you are mostly clear of the atmosphere make sure you are either at 0 throttle or out of fuel with the radial engines before you stage. Make sure you rocket is moving as straight as possible and decouple your radial tanks. Start your center stage burn a couple seconds after this to allow for the radials to clear some and make sure you do this at very low throttle and your center stage will slowly pull out from the middle of the opening radial tanks. The only time I have ever had any problems doing this is when I use to much throttle initially with the center stage....once your clear then you can throttle up as much as needed

[Festivefire]

if you want to use mods, then you can use tiny srbs from the kw pack, otherwise, make sure the decoupler is above the center of mass of the radial engines, and make sure that the radials are burned out and the center engine is going.