Propeller engines without plugins

[passinglurker]

Just something that idly crossed my mind but is it possible to make a propeller style engine in ksp without firespitter or some other plugin dependency? What would the limits and compromises be if it is remotely possible?

[Streetwind]

From a mechanical standpoint, a propeller engine is nothing special. It's just an airbreathing engine with a sharp thrust falloff between mach 0.6 and 0.8. To simulate that it pushes against the surrounding air, you build an air intake into the engine itself (i.e. it fulfills its own IntakeAir needs).

IIRC the plugin component of Firespitter is animation only - in other words, it makes the propeller actually look like it's spinning. In stock KSP, you cannot make a part that starts spinning when you stage it. You would have to either model your propeller as a semitransparent disk, faking the look of spinning at full speed (even in the editor and while the engine is off), or fly around with a propeller that doesn't spin at all.

Edited July 7, 2016 by Streetwind

[passinglurker]

16 minutes ago, Streetwind said:

From a mechanical standpoint, a propeller engine is nothing special. It's just an airbreathing engine with a sharp thrust falloff between mach 0.6 and 0.8. To simulate that it pushes against the surrounding air, you build an air intake into the engine itself (i.e. it fulfills its own IntakeAir needs).

IIRC the plugin component of Firespitter is animation only - in other words, it makes the propeller actually look like it's spinning. In stock KSP, you cannot make a part that starts spinning when you stage it. You would have to either model your propeller as a semitransparent disk, faking the look of spinning at full speed (even in the editor and while the engine is off), or fly around with a propeller that doesn't spin at all.

hmm... so is it possible to just give a part a constant spin and then "animate" an animations playback speed using FXModuleAnimateThrottle? if not could it be used to at least swap between states of looking full throttle, and shut off by rapidly shrinking and hiding what mesh is used?

[Streetwind]

I can't help you with that - I know configfile stuff, but with making assets I'm useless

[SpannerMonkey(smce)]

Hi the answer is yes you can make propeller style engines without firespitter, they use

		MODULE
	{
		name = FXModuleAnimateThrottle
		animationName = LBPdrive1
		responseSpeed = 0.3
		layer = 0
		dependOnEngineState = True
		dependOnThrottle = True
		weightOnOperational = True
		affectTime = false
		baseAnimSpeed = 0.5		// base + (throttle setting * multiplier)
		baseAnimSpeedMult = 100
		playInEditor = False
		animWrapMode = 2  	//	Default = 0	Once = 1		Clamp = 1	Loop = 2		PingPong = 4	ClampForever = 8
	}

And with a bit of tweaking you can get very satisfactory results, the engine below uses purely stock modules

[passinglurker]

@SpannerMonkey(smce) wow that's really impressive did you simply reconfig a fire spitter prop with stock modules or did you have to make something like that from scratch?

[Van Disaster]

The stock large turbofan has a visibly rotating ... fan, so I'd start there. ( FXModuleAnimateThrottle is apparently the place to look at ).

[SpannerMonkey(smce)]

4 hours ago, passinglurker said:

@SpannerMonkey(smce) wow that's really impressive did you simply reconfig a fire spitter prop with stock modules or did you have to make something like that from scratch?

It's all pretty much the same , except in the case of FXModuleAnimateThrottle the blades are a child of the spinner,  But yes it's  fairly easy to set up and certainly many levels behind things like wheels in level of difficulty. As for how easy it is to swap from using FS to using the FX module it really all depends on how the original part/model is assembled, without doubt it's always easier to start with the asset (dae,blend.fbx,obj) than starting with a pre compiled asset(.mu) Though even that is no real hold up if you are familiar with unity et al.

If you do decide to have a go at making one , and get stuck feel free to drop me a line

[NathanKell]

I explicitly added support for prop engines in 1.0.5's ModuleEngines changes, actually, so you can tune performance quite closely. You can vary fuel flow based on altitude and speed (to simulate turbo/superchargers) and thrust based on altitude and speed (thrust should be linear with density and taper off with speed with a sharp drop as the tips go supersonic--which is about M=0.6 to M=0.8 as said above).

[Azimech]

And if that's not enough and you want real propeller blades doing the work: stock turboprop engines have been here for a while.

To build a modded one in a nutshell: create a model of a turbine shaft and housing in a modeling program, export it to unity and give it a material with friction set to minimum for the bearings, create something to provide a thrust vector on the turbine shaft blades using ModuleEnginesFX and create propeller blades to stick to the end of the shaft. To start the engine: just decouple the shaft from the housing.

There are some limitations though: joint flexibility and collider integrity depends on part mass instead of material type (which is totally unrealistic in every conceivable way) which means the propeller blades start to expand and seem to "float" at higher angular velocities; it also means bearings fail without any good reason if parts are light, they "phase" through like ghosts going through a wall.

Also PhysX seems to have an upper limit of 50 rad/s (477 RPM) which really limits what can be done, but at least it's the most pure way of creating an engine instead of just an animation.

If you'd like more info, take a look at my topic in my sig.

 

[Azimech]

12 hours ago, NathanKell said:

I explicitly added support for prop engines in 1.0.5's ModuleEngines changes, actually, so you can tune performance quite closely. You can vary fuel flow based on altitude and speed (to simulate turbo/superchargers) and thrust based on altitude and speed (thrust should be linear with density and taper off with speed with a sharp drop as the tips go supersonic--which is about M=0.6 to M=0.8 as said above).

I have to thank you for that. ModuleEnginesFX and ModuleResourceConverter are the most versatile of them all. With these two I was able to program my ignition system for my piston engines and a whole lot of other things!

[SpannerMonkey(smce)]

12 hours ago, Azimech said:

And if that's not enough and you want real propeller blades doing the work: stock turboprop engines have been here for a while.

Slightly topic (cant get a tshaft airborne without it self destructing)  Where did you get the force 4 sea state from, small whitecaps? or is it just a graphical anomaly ?

[Van Disaster]

6 hours ago, SpannerMonkey(smce) said:

Slightly topic (cant get a tshaft airborne without it self destructing)  Where did you get the force 4 sea state from, small whitecaps? or is it just a graphical anomaly ?

Scatterer will do that if you tell it to. Haven't worked out how to set it up so it's actual waves instead of "there's about 8 weather systems around" yet.

Edited July 9, 2016 by Van Disaster

[Van Disaster]

Back on topic: how do you jump from startup rotation anim to fullspeed blurred disk with that plugin? and is there some combo of modules to let you have a startup delay? I note most of the FS prop engines seem to give full thrust as soon as the engine is enabled... I think one of the other engine plugins has a delay ( b9 perhaps ) and it's not hard to write, but that is a bit over the top.