Attempting to make a multi-engine interstage adapter.

[Galane]

Here's what I have so far for an interstage adapter to fit between two ThunderMax tanks. I plan on an upsized Kerbodyne decoupler to go with it. Why? Because I want to use those giant tanks in second stages instead of bundling Rockomax or Kerbodyne tanks together. One tank, no struts, several fewer parts.

Things to do yet and questions

1. Put 6 mounting nodes for LV size engines around it instead of 4. Doesn't look like room for 8, but probably will be on the ThunderMaximus version. Bolt circle calc with coordinates output. http://theoreticalmachinist.com/BoltCircleCalc

node_stack_bottom11 = 1.7, .78, 0, 0, 1, 0, 2
node_stack_bottom12 = .85, .78, -1.472, 0, 1, 0, 2
node_stack_bottom13 = -.85, .78, 1.472, 0, 1, 0, 2
node_stack_bottom14 = -1.7, .78, 0, 0, 1, 0, 2
node_stack_bottom15 = -.85, .78, -1.472, 0, 1, 0, 2
node_stack_bottom16 = .85, .78, -1.472, 0, 1, 0, 2

2. How do I get the decoupler to make a fairing when attached to the center bottom node? Anything special about the bottom node on engines? Make this a kind of dummy engine?

3. Strength? Will this bend and break at the bottom node? I could push the engines out a bit farther and increase the "peg" diameter.

4. I'd thought I'd have to figure out how to block fuel flow on just the center bottom node but then I realized that decouplers don't have fuel crossfeed. Whew! Tricky problem averted - and some crazy people might stick another engine on the "peg" and use this as a first stage engine mount with asparagus boosters.

PART
{
name = thunderInterstage
module = Part
author = Squad, Galane

MODEL
{
   model = Squad/Parts/FuelTank/MK1FuselageStructural/model
   position = 0, 1.15, 0
   scale = 5, .5, 5
   rotation = 0, 0, 0
// parent = anotherModelTransform	<---------Not necessary unless Second or subsequent part.
// texture = model000 , Squad/Parts/Command/probeCoreOcto/model000
// texture = model001 , Squad/Parts/FuelTank/fuelTank2-2/model001
}

MODEL
{
   model = Squad/Parts/FuelTank/MK1FuselageStructural/model
   position = 0, 0, 0
   scale = 2, 2, 2
   rotation = 0, 0, 0
// parent = anotherModelTransform	<---------Not necessary unless Second or subsequent part.
// texture = model000 , Squad/Parts/Command/probeCoreOcto/model000
// texture = model001 , Squad/Parts/FuelTank/fuelTank2-2/model001
}

rescaleFactor = 1.0

// --- node definitions ---
// definition format is Position X, Position Y, Position Z, Up X, Up Y, Up Z
node_stack_top = 0.0, 1.5, 0.0, 0.0, 1.0, 0.0, 3
node_stack_bottom1 = 0.0, -1.5, 0.0, 0.0, 1.0, 0.0, 3
node_stack_bottom11 = 0, .78, 1.7, 0.0, 1.0, 0, 2
node_stack_bottom12 = 0, .78, -1.7, 0.0, 1.0, 0, 2
node_stack_bottom13 = 1.7, .78, 0, 0.0, 1.0, 0, 2
node_stack_bottom14 = -1.7, .78, 0, 0.0, 1.0, 0, 2
node_attach = 1.25, 0.0, 0.0, 1.0, 0.0, 0.0, 1

TechRequired = veryHeavyRocketry
entryCost = 8800
cost = 3600
category = Structural
subcategory = 0
title = ThunderMax Interstage Adapter
manufacturer = AeroKerbin Thunder Division
description = AeroKerbin wants you to go to space today, with a ThunderMax second stage.

attachRules = 1,1,1,1,0
stackSymmetry = 3

mass = 4
dragModelType = default
maximum_drag = 0.2
minimum_drag = 0.3
angularDrag = 2
crashTolerance = 12
maxTemp = 2900
breakingForce = 1e37
breakingTorque = 1e37

}
}

[Galane]

Had a bit of a misplaced - sign. 6 LV engines proved to be too wimpy so I kicked the nodes out a little and fit 8 in the ThunderMax diameter. Now I'm thinking 10 could fit on the Maximus version.

PART
{
name = thunderInterstage
module = Part
author = Squad, Galane

MODEL
{
   model = Squad/Parts/FuelTank/MK1FuselageStructural/model
   position = 0, 1.15, 0
   scale = 5, .5, 5
   rotation = 0, 0, 0
// parent = anotherModelTransform	<---------Not necessary unless Second or subsequent part.
// texture = model000 , Squad/Parts/Command/probeCoreOcto/model000
// texture = model001 , Squad/Parts/FuelTank/fuelTank2-2/model001
}

MODEL
{
   model = Squad/Parts/FuelTank/MK1FuselageStructural/model
   position = 0, 0, 0
   scale = 2, 2, 2
   rotation = 0, 0, 0
// parent = anotherModelTransform	<---------Not necessary unless Second or subsequent part.
// texture = model000 , Squad/Parts/Command/probeCoreOcto/model000
// texture = model001 , Squad/Parts/FuelTank/fuelTank2-2/model001
}

rescaleFactor = 1.0

// --- node definitions ---
// definition format is Position X, Position Y, Position Z, Up X, Up Y, Up Z
node_stack_top = 0.0, 1.5, 0.0, 0.0, 1.0, 0.0, 3
node_stack_bottom1 = 0, -1.5, 0, 0, 1, 0, 3
node_stack_bottom11 =    1.8, .78,      0, 0, 1, 0, 2
node_stack_bottom12 =  1.273, .78,  1.273, 0, 1, 0, 2
node_stack_bottom13 =      0, .78,    1.8, 0, 1, 0, 2
node_stack_bottom14 = -1.273, .78,  1.273, 0, 1, 0, 2
node_stack_bottom15 =   -1.8, .78,      0, 0, 1, 0, 2
node_stack_bottom16 = -1.273, .78, -1.273, 0, 1, 0, 2
node_stack_bottom17 =      0, .78,   -1.8, 0, 1, 0, 2
node_stack_bottom18 =  1.273, .78, -1.273, 0, 1, 0, 2
node_attach = 1.25, 0.0, 0.0, 1.0, 0, 0, 1

TechRequired = veryHeavyRocketry
entryCost = 8800
cost = 3600
category = Structural
subcategory = 0
title = ThunderMax Interstage Adapter
manufacturer = AeroKerbin Thunder Division
description = AeroKerbin wants you to go to space today, with a ThunderMax second stage.

attachRules = 1,1,1,1,0
stackSymmetry = 7

mass = 4
dragModelType = default
maximum_drag = 0.2
minimum_drag = 0.3
angularDrag = 2
crashTolerance = 12
maxTemp = 2900
breakingForce = 1e37
breakingTorque = 1e37

}
}

That will lift a ThunderMax 64 tank with a small payload off the pad and nearly to orbit without a booster stage so given a kick up from a ThunderMax 128 with four mainsails and five LV it should carry on to orbit.

Still the issue of having a fairing around it all. A possibility that came to mind is removing the center peg and requiring a Mainsail in the middle to attach the large decoupler, then requiring a bunch of struts zigzagged across the gap. Not an elegant solution and somewhat defeats the concept of reducing parts count via really large fuel tanks.

As it is, it works with the stock Kerbodyne decoupler and is very solid in flight, but looks fugly.

4:48 AM so I should go to bed so I can get up in time for my 43rd birthday dinner today. ;-)

[RidingTheFlow]

Procedural Fairings already has interstage adapter, which supports huge diameters, and could easily accommodate massive engine clusters, I use it all the time. You may want to save some work (happy birthday BTW )

http://forum.kerbalspaceprogram.com/threads/39512-0-23-5-Procedural-Fairings-3-01-resize-able-bases-multi-adapter-(May-14)

Edited May 25, 2014 by RidingTheFlow

[Galane]

I'm trying to do it in a way that doesn't need any plugins, to go with my ReStock updates.

[frizzank]

Take a look at the multi engine plates and decoupler for Saturn V in FASA, I put an extra attach node at the bottom node for just the decouple.