Multistaging with nuclear engines

[Jarin]

So, I'm a huge fan of the LN-V engine. The efficency means that I have a ton of flexibility in my missions. That is... once I can get the nuclear-powered transit stage into orbit at all. And that's often the problem...

Pre-0.21, I would use the tri-splitter, attached to that flat adapter piece, then sorta fudge decouplers onto the bottom of all three engines (it often had clipping issues), attach another tri-splitter to bring things back together, then just strut the hell out of the entire assembly. This tended to work on about half of my launches, with the other half having engines randomly breaking off or exploding at separation. With .21 and the shiny new large-size quad separators, I thought my job would be easier. Indeed, there were no clipping issues with separators anymore... but now I can't get staging to succeed at all. Every dang time, I blow those separators and most or all of my nuclear engines go flying, often with their staging sheaths still attached.

Amusingly, my most successful design so far didn't even use separators on the engines... they just hung free above the main body, with the separation handled by a convoluted framework of cubic struts holding the top stage suspended above the lifter.

So... my fail-designs aside, how do folks here go about launching nuclear powered orbital vehicles?

[stupid_chris]

Are you using the stack separators or the decouplers? Those could cause issues.

Else, I don't put decouplers under nuclear engines if I attached them in symmetry. I either build launchers around the main body or find a way around without putting decouplers under.

[Xeldrak]

Hm, off course I have no good picture of my usual assembly. Here, look at the top vessel:

I will usually use a big, central fuel tank, then add 6 or 8 radial fueltanks and equip them with the nuclear engines. Then add fuellines, that pump the fuel from the core tank to the radial ones. Now the big decoupler goes to the bottom of the big fuel tank to connect the ship with its rocket. This way its very sturdy and the nuclear engines don't have to bear any load during ascend.

[Mr Shifty]

Yeah, you can't put tri-couplers both above and below your engines without doing something fancy with docking ports. The part tree requires that each part only have one parent (i.e. a single path back to the root part), so the tri-coupler below is only actually attached to one of your engines, which is what may be causing your problems.

[panarchist]

Jarin - I've been using this ship here: http://vanillaspaceagency.com/pathfinder-mk-8-nuclear/

(all stock parts)

Multiple decouplers will bounce off each other and cause the engines to go flying. I was able to successfully decouple them manually by right-clicking and doing it individually - the space bar does exactly as you describe.

[espm400]

Yeah, you can't put tri-couplers both above and below your engines without doing something fancy with docking ports. The part tree requires that each part only have one parent (i.e. a single path back to the root part), so the tri-coupler below is only actually attached to one of your engines, which is what may be causing your problems.

'Something fancy...'

Seriously though, I've posted this guy's video in these forums so many times. It's basically just a quick tutorial on how to use mulit-couplers and docking ports to be able to cheat the part tree.

[Jarin]

The part tree requires that each part only have one parent (i.e. a single path back to the root part), so the tri-coupler below is only actually attached to one of your engines, which is what may be causing your problems.

That explains so very much. I'll give that docking port idea a try.

Panarchist, I don't have KSP here, but I'll give that design a look this evening. Thanks!

[dlmarti]

This is my general purpose, in Kerbin influence vehicle.

https://www.dropbox.com/s/uovsk0a8jazgcqt/Fueler%20Mk6.craft

Its easy to launch and trivial to dock.

It is designed to refuel/rescue ships within Kerbin's influence.

Basically I launch a half dozen of these ships at lunch, then use them to refuel/push around other vehicles.

So at night I launch whatever mission, then switch over to a Fueler, and dock with the mission vehicle. The Fueler then pushes the mission vehicle to where it needs to go, and refuels it also.

[Captain Sierra]

I've never had an issue multi-staging with any engines. I rarely do it on upper stages that then require decouplers but mine (I'm still back on 20.2 but have the large splitters (KSPX) so I do use them) never have any problems when staging. I've even done setups where I have asparagus first stages and then a pancake upper using quad couplers to expand to 4 engines and the back down to a single core for the asparagus.

[4page]

Probably, the reason your engines are blowing up when you release the decouplers is because the ballast from the engines, the smooth round thing covering the engines, gets stuck in the middle of the engine clusters. Thus it detects the collisions and tries to move out way of them and breaks apart the engines. You need to rotate all the engines so that the lines are diagonal from the center of the 4 cluster.

[sojourner]

I think the forum averages a new thread on this every two days. Either we need a stickied thread with the solution in it or an improvement to the search function.

[Temstar]

Basically three ways that I know of:

1. Build the launch vehicle around the payload with LV-N engines

2. Build some kind of inter-stage structure on the centre node and put the payload onto of a regular booster rocket

3. Leave the top node of the payload clear and load it onto the booster rocket upside down