Need help with tweaking a custom engine

[Lazarus78]

Sorry if this is in the wrong place. The forums don't seem to really have a section fitting for this type of question.

Anyhoo, I made a custom engine, and by custom, I mean I duplicated an existing part and started messing with the settings.

The engine in question is an "ion" engine which I am trying to make with greater thrust and lower resource usage, unfortunately its not a matter of changing the thrust, as it seems the higher the thrust, proportionately so does the resource usage go up. So my "ion" engine with a thrust of 256 will drain all my ships 12000 electrical charge in a matter of seconds. This is not idea. I don't might high energy usage, but i don't want it draining faster then is usable.

Also, I would much prefer the engine to use ONLY electrical charge, but setting or removing the Xenon resource makes the engine not work at all. Is there a way to remove the gas requirement?

Relevant information:

// --- standard part parameters ---
mass = 2
dragModelType = default
maximum_drag = 0.2
minimum_drag = 0.2
angularDrag = 2
crashTolerance = 7
maxTemp = 3600

MODULE
{
	name = ModuleEngines
	thrustVectorTransformName = thrustTransform
	exhaustDamage = False
	ignitionThreshold = 0.1
	minThrust = 0
	maxThrust = 256
	heatProduction = 0
	PROPELLANT
	{
		name = ElectricCharge
       		ratio = 1.0
		DrawGauge = True
	}
	PROPELLANT
	{
		name = XenonGas
		ratio = 0.05
	}
	atmosphereCurve
 	{
   	 key = 0 256
 	}

}

Edited April 20, 2013 by Lazarus78

[EndlessWaves]

Both your questions stem from the fact that the engine module specifies fuel economy in ISP. ISP works out as mass use per unit thrust.

So increasing the thrust increases mass use, and you can't solely have a zero mass fuel because dividing mass flow by fuel density to get fuel weight results in a divide by zero error.

The first one is easily fixed by increasing the ISP.

The second one isn't, ModuleEngines doesn't support using only massless fuels.

You could potentially use the old 0.15 LiquidEngine class (not LiquidFuelEngine) but I don't know if that's been updated to support more modern introductions like action groups. Other than that, custom plugin time.

[Lazarus78]

So lowing the isp will lower the fuel consumption?

[EndlessWaves]

Increasing the ISP lowers the fuel consumption.

[Lazarus78]

ok, i got it sorted out. thanks a lot!

[Mekan1k]

You could make the engine 'generate' xenon, or another fuel, and use that for thrust..

[Lazarus78]

I made a separate part that does the generation to negate the gas usage.

[Mekan1k]

Those can be the same part

[RychschaX]

or....we could go the other route and make a different electricity resource that acts like a fuel.....I imagine crews about to run out of power when they orbit around to the day side of the planet...they hastily deploy their solar panels and begin to refill their electricity tanks....its no wonder third-world countries on Kerbin tend to not have power in many places. think of all the pipes they would need to run to get the electricity everywhere...wow....I should totally do something with this....