ModuleEngine

[Toonu]

Hello there,

I''ve been creating MM patch to edit one engine whole day today, because it had bad velocityCurve, but when I get deeper into it I found out I'm confused what curve do what. So here's my question...we're talking about jet and propeller engines

What's the difference between VelocityCurve VelCurve and VelCurveISP and between AtmosphereCurve, AtmCurve and AtmCurveISP ?

The velocity curves are in m/s or Mach number because I found both describen on forum and wiki.

AtmopshereCurves are all in key = atmopsheredensity - ISP or atmo density - ISP change (aka 0.8 from original ISP)

Why are in some engines all four curves and in some three or two?

Thanks for any replies!

 

Example of engine I found with 4 curves, two of same type

 

MODULE
{
    name = ModuleEngines
    thrustVectorTransformName = thrustTransform
    exhaustDamage = False
    ignitionThreshold = 0.1
    minThrust = 0
    maxThrust = 24
    heatProduction = 20
    useEngineResponseTime = True
    engineAccelerationSpeed = .1
    engineDecelerationSpeed = .3
    useVelocityCurve = True
    PROPELLANT
    {
        name = LiquidFuel
        ratio = 1
        DrawGauge = True
    }
    PROPELLANT
    {
        name = IntakeAir
        ignoreForIsp = True    
        ratio = 15
    }
    atmosphereCurve
    {
        key = 0 5940.09 0 0
    }
    
        atmChangeFlow = True
        useVelCurveIsp = False
        useVelCurve = True
        useAtmCurveIsp = False
        useAtmCurve = True
    
    velCurve
    {
        key = 0 1 4.000001 11.01643
        
        key = 0.05 1.3 0.05313873 -0.616887

        key = 0.1 0.8 -25.57013 -15.01741
        
        key = 0.15 0.4 -11.80952 -3.917985

        key = 0.17 0.05 -23.77079 -4.752584
        
        key = 0.2 0.025 -0.557031 0

        key = 0.3 0 0 0

    }
    atmCurve
    {
        key = 0 0 4.571429 2.067626

        key = 0.175 1 14.70059 40.1285

        key = 0.2 2.25 9.892332 7.831375

        key = 0.45 1
        
        key = 0.525 1.025

        key = 0.9 0.9

        key = 1 0.8

    }
    atmCurveIsp
    {
        key = 1 1
        key = 0.525 0.9
        key = 0.45 0.8
        key = 0.2 1
        key = 0.175 0.6
        key = 0 0
    }    
    velCurveIsp
    {
        key = 0 2
        key = 0.2 1.2
        key = 0.4 0.7
        key = 0.6 0.3
        key = 0.9 0.1
        key = 1.2 0.2
    }
    }
[/spoiler]

Toonu

EDIT1: Is the wiki of KSP up to date? Because the curves aren't there at all except vel and atmCurves

Edited December 16, 2017 by Toonu

[Toonu]

Okay, sorry for doublepost, but from one more source I read I understand it like this:

AtmCurve is hrust changing with pressure

AtmCurveISP is ISP changing with pressure

AtmosphereCurve is ISP changing with Pressure

VelCurve is in Mach speed changing thrust (decreasing with speed)

VelCurveISP is decreasing ISP with Mach number (or increasing...scramjets?)

VelocityCurve is in mps and is also changing thrust with speed, but instead of Mach the m/s?

Is it correct or I'm wrong (again  ) ?

Thanks for replies!

[blowfish]

Okay, as far as I can see here's what's what:

• atmosphereCurve - I_sp vs static pressure (atmospheres).  Always used.
• atmCurve - flow multiplier vs atmosphere density (normalized, i.e. 0-1).  Used if atmChangeFlow = true and useAtmCurve = true
• atmCurveISP - I_sp multiplier vs atmosphere density (normalized, i.e. 0-1).  Used if useAtmCurveIsp = true
• velCurve - flow multiplier vs mach number.  Used if useVelCurve = true
• velCurveIsp - I_sp multiplier vs mach number.  Used if useVelCurveIsp = true
• thrustCurve - flow multiplier vs amount of propellant left (normalized, i.e. 0-1).  Used if useThrustCurve = true.  Ignores any propellants with ignoreForThrustCurve = true
• throttleIspCurve - I_sp multiplier vs throttle (normalized, i.e. 0-1).  Used if useThrottleIspCurve = true
• throttleIspCurveAtmStrength - Modifier for how much throttleIspCurve actually affects I_sp vs static pressure (atmospheres).  0 means that throttleIspCurve doesn't affect I_sp at all, 1 means that throttleIspCurve has the full effect.  Used if useThrottleIspCurve = true

[Toonu]

Thanks a lot for this clear and up to date explanation. Actually I have one more question, how do you edit how much fuel per second engine consume? I heard its done via ISP of atmosphereCurve, is it true? Except the ration of fuel set inside the propellants.

EDIT: And the flow multiplier is flow of fuel I guess so its answer to my question, right?

EDIT2: Actually I found that atmCurve is for thrust vs pressure instead of flowMultiplier vs pressure, is it right?

SOurce: http://kspapi.forwoods.org/#/classes/ModuleEngines?scrollTo=atmCurve

Edited December 17, 2017 by Toonu

[blowfish]

Fuel flow is calculated from initial thrust and I_sp, then modified by all the flow modifying curves I mentioned.

atmCurve modifies flow at constant I_sp, so thrust and flow will both change proportionally.  This is the case for all the flow-modifying curves I mentioned above.  For the I_sp-modifying curves, it will modify the I_sp at constant fuel flow, so the thrust will also change.