Possible to make a part nothing can attach to?

[Galane]

What I want to do is cfg mod a stock part as a "throwaway" decoupler to which nothing can be attached, and also be physics-less in flight, and not actually separate anything from the craft so it creates no debris.

The purpose of it will be to have a 'control module' that can be stuck anywhere on a rocket then put its icon into a stage with engines. That will satisfy MechJeb's requirement to have a decoupler or separator in any stage with engines so that its auto staging will not fire engines prematurely.

One use for it would be to block MJ from firing sepratrons intended to be used for deorbiting. Mount some of those pointing upwards along with a small probe body and one of these little gizmos, then put the icons for the sepratrons and non-decoupler way up high in the stack.

MechJeb's auto staging will then "skip over" their physical location. After the payload is in orbit the player can switch to the spent stage, orient it for deorbit and smack the spacebar to fire the sepratrons.

Integrating decoupler technology into the Sepratrons would serve the purpose, but a standalone device would work for any craft design.

Sticking on an extra TT-38K works but it has mass, drag and pops off a piece of debris.

[CaptainKipard]

I don't know about mechjeb or anything else but to disallow attaching you do this:

// attachment rules: stack, srfAttach, allowStack, allowSrfAttach, allowCollision
attachRules = 1,1,0,0,1

[Galane]

Here's what I have edited. Started with a copy of the TT-38K, switched model to the OKTO2. Need to test and see what setting the force to 0 does. Would be nice if that makes it stay attached.

PART
{
name = notaDecoupler
module = Part
author = NovaSilisko, Galane

MODEL
{
   model = Squad/Parts/Command/probeCoreOcto2/model
   position = 0.0, 0.0, 0.0
   scale = .5, 1.0, .5
   rotation = 0.0, 0, 0
}
scale = 1
rescaleFactor = 1

node_attach = 0.01, 0.0, 0.0, 1.0, 0.0, 0.0

//fx_gasBurst_white = -1.16832, 0.0, -0.0826454, -1.0, 0.0, 0.0, decouple
sound_vent_large = decouple

TechRequired = stability
entryCost = 1200
cost = 25
category = Structural
subcategory = 0
title = NOTA Decoupler
manufacturer = Alan Aerospace Recycling & Packaging
description = The NOTA is not a decoupler. Nothing can be connected to it. Its sole reason for existing is to ensure that 

autopilots do not prematurely activate engines. AARP's engineers are attempting to make it stay attached to the rocket after 

activation so it doesn't become more debris in space.

attachRules = 1,1,0,0,1

mass = 0.005
dragModelType = default
maximum_drag = 0.2
minimum_drag = 0.2
angularDrag = 1
crashTolerance = 8
maxTemp = 3200
stagingIcon = DECOUPLER_HOR

PhysicsSignificance = 1

stageOffset = 1
childStageOffset = 1


MODULE
{
    name = ModuleAnchoredDecoupler
    anchorName = anchor
    ejectionForce = 0
	explosiveNodeID = srf
}
MODULE
{
	name = ModuleTestSubject

	// nowhere: 0, srf: 1, ocean: 2, atmo: 4, space: 8
	environments = 15

	useStaging = True
	useEvent = False
}