How to apply a Velocity Curve on an engine not requiring Air.

[Xurkitree]

As a test, I tried applying a velocity curve to a rocket engine, but apparently adding a velocity curve makes it require air for some reason, eventhough IntakeAir isnt declared anywhere in the CFG.

Any help? AS for why, I won't tell now.

[Mecripp]

1 hour ago, Xurkitree said:

As a test, I tried applying a velocity curve to a rocket engine, but apparently adding a velocity curve makes it require air for some reason, eventhough IntakeAir isnt declared anywhere in the CFG.

Any help? AS for why, I won't tell now.

More then likely you just edited the cfg wrong and just copied a jet engine over a rocket engine and there was this plugin

 

[JadeOfMaar]

 @Xurkitree What you are trying to arrange is an air-augmented rocket engine. Some exist in Mk2 and Mk3 Stockalike Expansion. Mods aside..... In addition to needing a float curve editor (linked above) for advanced curve tweaking, you will need to setup the following situation:

MODULE
{
	name = ModuleEngines(FX)
	// stuff
	
	atmChangeFlow = True // you might need this. you might not
	useVelCurve = True
	velCurve
	{
		key = 0 1 0 0
		key = 4 2 0 0
		key = 7 1 0 0
	}
}

The four numbers in each key are: speed (Mach number); thrust multiplier; tangent in; tangent out. The zeroes for tangents ensure that (in most cases) the curve does not bend too freely and potentially cause large spikes or drops in thrust.

Be advised that you will eventually experience the weird phenomenon where if you leave the atmosphere while your thrust is buffed by the velocity curve (depends on how steeply you ascend and your mach speed at that point) it will flatten out in a snap. The higher the buff, the more obvious it is.

 

 

[Xurkitree]

8 hours ago, JadeOfMaar said:

[snip]

No, I'm not trying to make an Air-Augumented Rocket Engine, I'm trying to make a vacuum optimized engine that gains better thrust the faster its going in space. The problem is that on adding the velocity curve, it seems to behave a like a jet engine, in the sense that it only works in atmosphere, upto a certain altitude, but since its a rocket engine, it only consumes liquid fuel and oxidizer. Is there any solution for that? Is is a lazy quirk of the way Squad coded in the jet engines, linking jet engine behaviour with velocity curve, even though it shouldn't be this way??

[Yes I know its weird and impossible, but hey! its something]

Edited December 16, 2018 by Xurkitree

[Mecripp]

1 hour ago, Xurkitree said:

No, I'm not trying to make an Air-Augumented Rocket Engine, I'm trying to make a vacuum optimized engine that gains better thrust the faster its going in space. The problem is that on adding the velocity curve, it seems to behave a like a jet engine, in the sense that it only works in atmosphere, upto a certain altitude, but since its a rocket engine, it only consumes liquid fuel and oxidizer. Is there any solution for that? Is is a lazy quirk of the way Squad coded in the jet engines, linking jet engine behaviour with velocity curve, even though it shouldn't be this way??

[Yes I know its weird and impossible, but hey! its something]

You just wanting a rocket engine to use liquid fuel ?

[JadeOfMaar]

@Xurkitree I assumed air-augmented is what you wanted as the velocity curve is only relevant in atmosphere and with engines that rely on airspeed and pressure to rise in performance. (For turbine engines, fast air helps to push the turbine blades, making them spin faster and more easily, adding to thrust and efficiency within their operating ranges. For ram engines, air that comes in fast enough is compressed and superheated, then the engine just has to squirt fuel into it, or leverage the air pressure to produce thrust.)

This is not how it works at all with rockets. Pumps and plumbing aside, what matters are these three details at the end of things: The propellant (which has the most significance in the Isp you get); The shape of the exhaust nozzle for that propellant and the desired situation; The ambient pressure where the engine is being used.

TL;DR
Concerning KSP physics and your request, there's nothing wrong and nothing missing, but your understanding of how engines work has only just begun. What you're asking for does not make sense.

[Mecripp]

Maybe you should look here https://en.wikipedia.org/wiki/Rocket_engine

and https://en.wikipedia.org/wiki/Jet_engine

[Xurkitree]

I know it doesn't make sense, which is why I'm doing it. I'm trying making things which completely break the programmed laws of physics within the game - utterly bizzare, practical joke like, stupidly op at time parts.

I know rocket engines don't increase in efficiency with velocity, while high speed jet engines like ram/scram jets do due to the increased air supply.

Anyways, apparently after some further testing I have found that velCurves only apply when the body is flying and therefore doesn't apply in space.

Edited December 16, 2018 by Xurkitree

[JadeOfMaar]

2 minutes ago, Xurkitree said:

I know it doesn't make sense, which is why I'm doing it.

Umm... okay. I wish you well with that.