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I've been working on moving the RD-107/108 from KW into the RP-0 tech tree to simulate the R-7. Since the 107/108 series used HTP to spin the turbopumps, I've converted them to tripropellant engines. Using the Soyuz 11A511U-0 booster as a guide: Gross mass: 44,500 kg (includes 1190 kg of hydrogen peroxide) Dry mass: 4,064 kg (includes 280 kg LN2) LOX+Kero+H2O2 mass: ~40,400 kg LOX+Kero mass: ~39200 kg Ratio (LOX+Kero)/H2O2: 97/3 So the engines consumed approximately an additional 3% (3.1% really I think) of the total propellant mass in H2O2. Since Isp = thrust*time/propmass, the Isp including H2O2 should be approximately 3% lower (100/103.1). I've subtracted .015 from the mixture ratio for Kero and LOX and added in .03 HTP. This is by volume not by mass and HTP has a higher density than LOX or Kero, so if someone wants to calculate the exact ratio that would be good. I've also multiplied all the Isp values by .97 and rounded to account for the HTP being a propellant. Haven't touched the cost numbers, but I feel like all the engines should be more expensive than they currently are. If someone can check my math, that would be great since I'm a biologist and can't be trusted with numbers If the numbers check out, I can go through and add in further variants of the RD-107/108 to be unlocked through the tech tree. // KW Rocketry Griffon-G8D, now RD-107/108 @PART[KW2mengineGriffonG8D]:AFTER[RealismOverhaul] { %description = The RD-107 and RD-108 are first stage/sustainer engines burning semi-cryogenic propellant. Gas generator. Combustion instability in larger nozzles led to a design with four combustion chambers fed by single turbopump. The turbopump was powered by the decomposition of hydrogen peroxide, which contributed no thrust. Sputnik, the first artificial satellite, was launched on a modified R-7 missile using four RD-107 strap-on boosters and an RD-108 sustainer core. Later versions of these engines powered the Vostok, Voskhod, Molniya, and Soyuz launchers, which all trace their design to the R-7 missile. %mass = 1.2 %TechRequired = basicRocketry @MODULE[ModuleEngines*] { %minThrust = 971 %maxThrust = 971 @atmosphereCurve { @key,0 = 0 297 @key,1 = 1 243 } } !MODULE[ModuleEngineConfigs] {} MODULE { name = ModuleEngineConfigs type = ModuleEngines configuration = RD-107-8D74 modded = false origMass = 1.2 CONFIG { name = RD-107-8D74 minThrust = 971 maxThrust = 971 heatProduction = 100 PROPELLANT { name = Kerosene ratio = 0.345 DrawGauge = True } PROPELLANT { name = LqdOxygen ratio = 0.625 } PROPELLANT { name = HTP ratio = 0.03 } atmosphereCurve { key = 0 297 key = 1 243 } } CONFIG { name = RD-108-8D74 minThrust = 912 maxThrust = 912 heatProduction = 100 cost = 50 PROPELLANT { name = Kerosene ratio = 0.345 DrawGauge = True } PROPELLANT { name = LqdOxygen ratio = 0.625 } PROPELLANT { name = HTP ratio = 0.03 } atmosphereCurve { key = 0 299 key = 1 234 } massMult = 1.083 } CONFIG { name = RD-107-8D74K minThrust = 995.3 maxThrust = 995.3 heatProduction = 100 cost = 150 PROPELLANT { name = Kerosene ratio = 0.345 DrawGauge = True } PROPELLANT { name = LqdOxygen ratio = 0.625 } PROPELLANT { name = HTP ratio = 0.03 } atmosphereCurve { key = 0 305 key = 1 250 } massMult = 1.0 techRequired = advRocketry } CONFIG { name = RD-108-8D75K minThrust = 941 maxThrust = 941 heatProduction = 100 cost = 200 PROPELLANT { name = Kerosene ratio = 0.345 DrawGauge = True } PROPELLANT { name = LqdOxygen ratio = 0.625 } PROPELLANT { name = HTP ratio = 0.03 } atmosphereCurve { key = 0 306 key = 1 241 } massMult = 1.083 techRequired = advRocketry } } !MODULE[ModuleEngineIgnitor] {} MODULE { name = ModuleEngineIgnitor ignitionsAvailable = 1 autoIgnitionTemperature = 700 ignitorType = Electric useUllageSimulation = True isPressureFed = False IGNITOR_RESOURCE { name = ElectricCharge amount = 0.5 } } }