Radial decoupler, my greatest nemesis.

[FreedomFighterEx]

It's seem to be the best part to sabotage your rocket if your rocket not stabilize still enough when it staging off, part that attach to it mostly crash right into main rocket or engine, i don't know if it's just because my bad design but most of time my rocket fail because of this, maybe it's because the force way too weak for larger part even with the one that offer large distant still not enough if the force is too low, part still fall and ram right into it and then spin off and ram into main rocket.

[Scotius]

Don't decouple while your rocket is changing the course (during gravity turn, or while chasing the apoapsis). Check if your staging is set correctly - you should decouple from outside towards the center, and from the bottom upwards. If it still doesnt work - use sepratrons to push spent parts away from your core rocket.

[CalculusWarrior]

Also you can try using the Sepatron solid rocket boosters. Simply rotate them with WASD, Q, & E (you can hold shift to rotate them with more precision), and orient them so that their exhaust is pointed towards your rocket, then set them up so that they fire when the radial decoupler separates. This makes sure that they get a bit more of a kick than the decoupler alone can give them.

However, make sure that you place the Sepatrons so that they are approximately aligned with the centre of mass of your debris (ie: near the middle). Off-axis placement will just cause your debris to spin out of control and hit your main rocket.

Happy decoupling!

[rosenkranz]

a note on that CoM comment. Putting it at the center of the tank is not the CoM because the tank is now empty and weighs near to nothing. Even a big orange tanks doesn't weigh much empty while that mainsail still weighs 5 tons. I usually place the sepatrons a lot lower to comensate.

[Xaryn Mar]

If I remember correctly then the decoupler with "legs" is not the strongest of them. That would be the wide flat one.

Xaryn Mar.

[Brotoro]

There currently is (what I believe is) a bug that keeps the separation force from decouplers from working if you have struts connecting the parts. In lieu of the decoupler force working, you will need to use Sepatron motors to push the jettisoned parts away. Be sure to position the motors so their exhaust flames don't cause damage to the remaining parts of your rocket. I place mine a little ahead of the dropped booster's center of gravity so I get mostly push with a little peel-away rotation.

[BFalcon]

I always place my sepatrons so they angle towards the other tanks I'll be ejecting and mount them in pairs, one each side. This prevents damage to the rocket itself. I also mount mine slightly above the CoM so that they peel off, this then works reasonably ok if you need to eject while under power (NOT recommended, but if the alternative is complete control loss due to damage elsewhere, better to be safe than sorry). You CAN, if you double up on them, eject SRBs like that, if you get it just right, but I really do NOT recommend trying that. I found out this last one by mistake since I swapped stage a fraction early one time and it survived...

Get the positioning right, though, and you'll get a nice star-shaped pattern behind your rocket when you eject them.

One thing - don't worry too much about damaging other tanks which will be ejected if you're doing staggered ejections (ie one pair, then the next, then the next, etc) - they should survive at least 2 ejections next door each before complaining, by which time you'll be ready to eject the last pair.

[FreedomFighterEx]

for real, i kinda disappointed how small fuel tank peel off when eject it off, it look great but when fuel tank get bigger it just slide down.

ofc i try to keep my rocket still when eject it but anything that can go wrong will go wrong, to make the matter worse, sometime it has split second lag when eject it and sometime it end up with explosive.

i wish the decoupler have stronger force so it will push the object that attach with it away.

[foamyesque]

for real, i kinda disappointed how small fuel tank peel off when eject it off, it look great but when fuel tank get bigger it just slide down.

ofc i try to keep my rocket still when eject it but anything that can go wrong will go wrong, to make the matter worse, sometime it has split second lag when eject it and sometime it end up with explosive.

i wish the decoupler have stronger force so it will push the object that attach with it away.

That's what sepratrons are for. Like so:

See those little lights on the jettisoned tanks? That's the sepratrons burning. They're really handy little things.

[loppnessmonsta]

I've tried using sepratrons, but getting them near center-mass is frustrating, and if you're off by even a little bit it usually just makes the problem worse. So, until we have a vertical snap and "find center mass of this chunk" tool, I've opted for a different solution: I space my stuff out further. I typically only have 4 2m stacks around my center 2m stack, separated by the tall radial decoupler, which is attached to the 8 1m tanks around the base of the main stack. This gives them enough room to twist and turn while falling away that, even with more 1m tanks in between, they don't smack into anything.

[Awaras]

I've tried using sepratrons, but getting them near center-mass is frustrating, and if you're off by even a little bit it usually just makes the problem worse. So, until we have a vertical snap and "find center mass of this chunk" tool, I've opted for a different solution: I space my stuff out further. I typically only have 4 2m stacks around my center 2m stack, separated by the tall radial decoupler, which is attached to the 8 1m tanks around the base of the main stack. This gives them enough room to twist and turn while falling away that, even with more 1m tanks in between, they don't smack into anything.

You do not need to put them at the center of mass. Just put a pair on top of your stack and a pair on the bottom, near the engine. Because the engine has a greater mass than empty fuel tanks, the top of the jettisoned stage will move away from the center of your rocket faster than the bottom, keeping the jettisoned stage away from your rocket's center and giving you a nice 'flowering' effect.

Edited April 25, 2013 by Awaras

[magnemoe]

You do not need to put them at the center of mass. Just put a pair on top of your stack and a pair on the bottom, near the engine. Because the engine has a greater mass than empty fuel tanks, the top of the jettisoned stage will move away from the center of your rocket faster than the bottom, keeping the jettisoned stage away from your rocket's center and giving you a nice 'flowering' effect.

I always put them on top facing inward. As you are under trust the bottom part is below your rocket a fraction of an second after decoupling, the top part might hit the center stage or usualy the other boosters and the top placement let you only use one and and the seperatron rotate it outward.

You might get warning messages about damage on center booster but has never gotten any problems with it even with two orange tanks length boosters.

Only time I had problems was then dropping boosters without trust, rocket underway to Eve and Gilly, kept the last two boosters as drop tanks for the nuclear engine. During the adjustments for aerobraking they run dry so I press space while not under trust, the boosters rotated around center of mass and their tops hit and destroyed the nuclear engine, I should have separated them manually and done a short burn to get away.

First pass aerobraked nicely, the second pass was an crash, I managed to land the Eve lander, but the mapper and Gilly probe was lost.

[FreedomFighterEx]

so, any pic to explain the placement? sometime i get it right on some rocket but sometime it's not

[magnemoe]

so, any pic to explain the placement? sometime i get it right on some rocket but sometime it's not

Here is one simple one.

another view

seperatron trigger on decouple, I always put the fins on top as the off center drag help separate them, with only four boosters I would not use seperatrons here.

Another tips I did not use here is to make the booster larger than the main stage to get better TWR

Shows this well, this use three way symmetry because of the design of the base.

six long boosters three shorter ones, an nuclear transfer stage I start at 5000m.

Idea here is that the outer boosters don't lift the cargo, only the fuel. the three inner ones is responsible for lifting the base so you give them less fuel.

Base at Gilly keept the skycrane on top so I can move it. Yes the skycrane is overkill as I can also land it on Mun.

[royying]

press Q/E let the ship spinning then decouple

simple rule of circular motion:)

[ComradeGoat]

A sepatron on the inner edge of each tank at the bottom will tip the top away from the rocket, so that it angles outwards. This works regardless of where your COM is. All it needs to do is make the inside fall slightly slower than the outside.

[Saberus]

Personally I use a mix of sepratrons and control surfaces to peel off the empties. A pair of R8 winglets angled to deflect the top away from the main mass works wonders, and adds a touch of stability to the craft, and I found that trick watching Pebble Garden's videos. A little nudge near the top from a sepratron really helps, as well as something that causes either drag or lift away from the ship.

In space, the spinning technique is perfect, as the conservation of momentum flings the discarded stage from the main mass, then quickly ceasing the roll to make maneuvering easier. If you need sepratrons to remove parts in space, you might be doing it wrong.

[Dex Luther]

Playing through Career type mode, I've been having most of my issues attaching things like Solid fuel tanks to the radial decouplers. Either I get it so it looks like the tank is attached to the radial decoupler but when I go to the launch pad, the tank just falls over and explodes. Or I get it so it looks like it's attached to the radial decoupler, but when activate it, the tank doesn't decouple. Since I'm in career mode, I don't have access to much yet and it makes it pretty hard to advance further.

[jtaylor996]

I've had the best luck by just using 3 hydraulic decouplers along the really big boosters (Thor). I think that part is technically only attached to one, but 450 decouple force for each of the extras had to go somewhere. This setup ejects the boosters plenty far from the main body that I've had zero failures since.

[Starwhip]

The sepatron motors are great for heavier tanks, the large orange size. I put them at the top of the tank, pointing vertical, tilted about 5-10 degrees to the center. When you decouple, the stage gets a retrograde thrust as well as peeling away from your main engine. Works like a charm every time.

[profesorfrink42]

You don't have to put your sepratrons in the CoM of the empty tank if you use two of them at near-balanced places.

What I highly suggest is putting your radial boosters just a bit below your "main" rocket, and using a sepraton placed highly over the CoM of the empty rocket.

That way, it will naturally spin towards the center (where your main engine will be) but it won't touch the main engine.

Still, I suggest using two pairs of sepratrons: a pair over the CoM and another below.

Using pairs is obviously done to prevent spinning (which can lead to unexpected consequences)

[Sof]

Putting the decouplers high up, and then a couple of seperatrons pointing inwards just beneath the decoupler works for me.

Its also worth noting the decoupler force in the parts menu. If I remember correctly, the manifold has a higher explosive force so they should push you out further.

[Deadpangod3]

I put some trusses on the radial decouplers and then put an srb on those, then I strut them together, they end up falling away doing flips because the decoupler touches a winglet underneath but doesn't break it, the SRB pulls it down throwing it into a spin, it decouples quite nicely, never had a single accident beside forgetting struts.

[MalfunctionM1Ke]

Hey Fighter, do it like this but will full thrust. I was just showing something so I cut the throttle at staging.

Also note, that an outer Stage struttet to the inner stage will delete all decouple force, so you Need Sepatrons to implemet a force pushing the stage away.

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Edited October 22, 2013 by MalfunctionM1Ke

[allmhuran]

For what it's worth, there is currently a bug with decouplers where they apply no ejection force if the part is also strutted. Hence the need for sepratrons where you might not normally think they would be needed.