Sepratron Frustrations

[Valiant Corvus]

So I needed a heavy-ish lander for Minmus to do some jump hopping from landing sight to landing sight for some contracts, and I had a problem with parts colliding with each other when trying to get into orbit. So my line of thinking was then "Okay, so how about sepratrons to push the parts away from each other?". I added them in, put the staging in the right order, and did about 4-5 missions successfully before calling it a day.

The next day I load up the rocket and try to do some missions, but now the sepratrons on the 2nd stage just fly off without doing anything and the rocket collides with itself.

The first stage fires fine and separates fine.

However, the 2nd stage ones just fly right off and the rocket collides with itself.

What baffles me is that it wasn't doing this the other day. Help?

Edited January 22, 2015 by Claw

[wibou]

I had the same problem before. I found that the _SPEED_ at which you stage makes enormous difference on the success or failure (in the sense of if it hits the rocket or not) of decoupler / separatrons. I think there is even a bug open about it ("decoupler behave different depending the speed").

What I would recommend you would be to CUT the engine prior to activating your stage. I have very good and reliable rocket that just can't decouple unless I manually stage it using the "hit X / hit space / (wait 1 second) / hit Z" trick. Sure, you lose some delta-V but your kerbals live to see space that day

[Rosco P. Coltrane]

Nevermind. I got it all wrong.

[biohazard15]

Looks like a radial decoupler bug. Download bugfix modules from Claw here and see if it helps.

[Valiant Corvus]

Looks like a radial decoupler bug. Download bugfix modules from Claw here and see if it helps.

Worked like a charm, the rockets now separate properly.

Thanks a bunch.

[NASAHireMe]

Looks like a radial decoupler bug. Download bugfix modules from Claw here and see if it helps.

I wonder how many times people have to post in these "Gameplay Questions" forums before the moderators realize they should sticky Claw's radial decoupler bug thread. Because questions like these seem to come up every day on the forum.

[tsotha]

You really only need one seppy per tank. Put it on the top outside edge pointing directly outward and set the fuel to the minimum amount. All you're trying to do is keep the top of the tank from drifting in after it's ejected, and a 0.3 second burst from the sepratron will do that. The reason you want to cut the fuel down is otherwise it will damage your main stack.

As to why it worked before and doesn't work now, I have no idea. I would try moving them in the VAB and seeing if that makes a difference.

[Foxster]

You can often get away with zero sepratrons if you mount the decouplers low on the tank of the next stage and put the current stage tanks low on the the decouplers. Does make the craft taller but saves some parts and bother.

[eddiew]

You can often get away with zero sepratrons if you mount the decouplers low on the tank of the next stage and put the current stage tanks low on the the decouplers. Does make the craft taller but saves some parts and bother.

Using Claw's bugfix (as above) I've actually forgotten about sepratrons Nothing at 2.5m or below seems to need them, even with the most basic radial decoupler.

That said I'm also mounting radials lower than the central tank where the OP has them a little higher. By having the outermost engines the furthest back, you give them less time to whack into your ship as they detach

[Mighty1]

You could also spin the craft before the fuel runs out. The centrifugal force will push the empty stages away. No seperatron needed.