Engine Part, With No Propellants.

[Beale]

Hi, I've recently been trying to create a cheaty "dark matter" engine which doesn't use any fuel.

The model part works great and can be placed on the ship as expected ( The model is just a re-sized ION engine ).

Problem is that the engine can't produce any thrust no matter what I do. The engine has a "fuel-flow" counter in game, always at 0, despite it not needing any fuel.

The part.cfg is below.

PART
{
name = darkMatterEngine
module = Part
author = Beale

mesh = model.mu
scale = 1
rescaleFactor = 2

node_stack_top = 0.0, 0.2135562, 0.0, 0.0, 1.0, 0.0, 1
node_stack_bottom = 0.0, -0.1872844, 0.0, 0.0, 1.0, 0.0, 1

fx_exhaustFlame_blue_small = 0.0, -1.6, 0.0, 0.0, 1.0, 0.0, running
fx_exhaustLight_blue = 0.0, -1.6, 0.0, 0.0, 0.0, 1.0, running

cost = 5700
category = Propulsion
subcategory = 0
title = Dark Matter Engine 
manufacturer = Kerbal Experimental Propulsion Ltd.
description = By mixing dark matter with regular matter, this engine manages to produce a large amount of thrust, seemingly without any fuel.
attachRules = 1,0,1,1,0

sound_vent_medium = engage
sound_rocket_hard = running
sound_vent_soft = disengage
sound_explosion_low = flameout

// --- standard part parameters ---
mass = 0.5
dragModelType = default
maximum_drag = 0.4
minimum_drag = 0.4
angularDrag = 2
crashTolerance = 9
maxTemp = 3600

MODULE
{
	name = ModuleEngines
	thrustVectorTransformName = thrustTransform
	exhaustDamage = False
	ignitionThreshold = 0.1
	minThrust = 0
	maxThrust = 100
	fxOffset = 0, 0, 1.6

	atmosphereCurve
 	{
   	 key = 0 440
  	 key = 1 220
 	}
}

MODULE
{
      name = FXModuleAnimateThrottle
      animationName = colorAnimation
      dependOnEngineState = True
      responseSpeed = 0.5
}
}

[FireStormOOO]

Think about it this way: the engine class models reactive engines. Period. It takes an specific impulse value, and a thrust value, and asks "how much mass do I need to move to produce this thrust". Yours is not a reactive engine in the sense that it doesn't need reaction mass. It is an easy fix/workaround though. Just add a resource called dark matter that has a non-zero density, make your engine run purely on that, and add an alternator or generator that produces it. That provides your reaction mass, still without requiring fuel tanks.

Edited June 13, 2013 by FireStormOOO

[FireStormOOO]

I think if you wanted an engine with "no propellants" though, you'd have to write your own non-reactive engine class.

[Beale]

Alright, makes sense.

So would something like this in the parts.cfg,

MODULE
{
	name = ModuleGenerator
	isAlwaysActive = true
	OUTPUT_RESOURCE
	{
	   name = DarkMatter
	   rate = 1.0
	}	
}

something like this in the propellant bit

MODULE
{
	name = ModuleEngines
	thrustVectorTransformName = thrustTransform
	exhaustDamage = False
	ignitionThreshold = 0.1
	minThrust = 0
	maxThrust = 100
	fxOffset = 0, 0, 1.6

	PROPELLANT
	{
		name = DarkMatter
		ratio = 0.5
	}

	atmosphereCurve
 	{
   	 key = 0 440
  	 key = 1 220
 	}
}

and this in Kerbal Space Program\GameData\Squad\Resources\ResourcesDarkMatter.cfg

RESOURCE_DEFINITION
{
  name = DarkMatter
  density = 0
  flowMode = ALL_VESSEL
  transfer = PUMP
}

do the trick? Thanks for the help.

[Beale]

Right, I've added a new "DarkMatter" resource to the default resources file. The engine has a new

MODULE

{

name = ModuleAlternator

isAlwaysActive = true

RESOURCE

{

name = DarkMatter

rate = 1.0

}

}

that generates the energy, as well as a

RESOURCE

{

name = DarkMatter

amount = 500

maxAmount = 500

}

that should work as storage? (Not sure about this).

Trouble is, the engine always has a flame-out now on launch, with the message "DarkMatter deprived".

[FireStormOOO]

You have to make the DM resource have non-zero density, otherwise any amount of the resource still has no mass, and can't work in a reaction engine.