diff --git a/GameData/RealismOverhaul/Engine_Configs/AJ10_Adv_Config.cfg b/GameData/RealismOverhaul/Engine_Configs/AJ10_Adv_Config.cfg
index 7b123ab1f0..28dbf7dd39 100644
--- a/GameData/RealismOverhaul/Engine_Configs/AJ10_Adv_Config.cfg
+++ b/GameData/RealismOverhaul/Engine_Configs/AJ10_Adv_Config.cfg
@@ -49,8 +49,24 @@
 //	Nozzle Ratio: 65
 //	Ignitions: Infinite
 //	=================================================================================
+//	AJ10-133-Hylas
+//	Hylas
+//
+//	Dry Mass: 81 kg		larger nozzle, thinner ablative liner?
+//	Thrust (SL): ??? kN
+//	Thrust (Vac): 26.7 kN
+//	ISP: 1 @0.355 atm / 433 Vac		SL calculated with RPA
+//	Burn Time: 450		"ablation essentially zero (...) for durations up to 300 sec". 1.5x?
+//	Chamber Pressure: 0.28 MPa
+//	Propellant: LOX / LH2
+//	Prop Ratio: 5.0
+//	Throttle: N/A
+//	Nozzle Ratio: 40
+//	Ignitions: 9?	GE Apollo SPS had thicker ablative liner to support more restarts
+//	=================================================================================
 //	AJ10-133
 //	GE Apollo
+//	GE Apollo propulsion system used thrust chamber developed for Hylas, with shorter nozzle to fit on D-2
 //
 //	Dry Mass: 81 Kg
 //	Thrust (SL): ??? kN
@@ -68,11 +84,17 @@
 //	Sources:
 
 //	Purdue Engineering - AJ10-118K:				https://engineering.purdue.edu/~propulsi/propulsion/rockets/liquids/aj10-118k.html
-//	Aerojet General Space Engines:				http://www.alternatewars.com/BBOW/Space_Engines/Aerojet_Engines.htm
+//	Aerojet General Space Engines:				https://web.archive.org/web/20200229064124/http://www.alternatewars.com/BBOW/Space_Engines/Aerojet_Engines.htm
 //	Encyclopedia Astronautica - AJ10-118K:		http://www.astronautix.com/engines/aj10118k.htm
 //	Aerojet Rocketdyne - AJ10-118K:				https://www.rocket.com/delta-ii-stage-2-engine
 //	Norbert Brügge - US Space Rocket Engines:	http://www.b14643.de/Spacerockets/Diverse/U.S._Rocket_engines/engines.htm
 //	Spaceflight 101 - Delta II 7920:			http://spaceflight101.com/spacerockets/delta-ii-7920/
+//	https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=16154.0;attach=116872
+//	http://www.astronautix.com/t/thorhydra.html
+//	https://www.google.com/books/edition/Technical_Abstract_Bulletin/4SPJ4687C_AC?hl=en&gbpv=1&dq=AF+Contract+04(611)-5170&pg=RA2-PA189&printsec=frontcover
+//	https://www.holderaerospace.com/downloads/Technical_Papers/VaPak%20Systems%20Overview.pdf
+//	https://ntrs.nasa.gov/api/citations/19650010102/downloads/19650010102.pdf
+//	https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30092.0;attach=467003
 //	A Historical Look at US Launch Vehicles.PDF
 
 //	Used by:
@@ -313,6 +335,57 @@
 			}
 		}
 		
+		CONFIG
+		{
+			name = AJ10-133-Hylas
+			description = AJ10 variant burning liquid hydrogen and oxygen, proposed for use on the Hylas upper stage. Extremely low chamber pressure and autogeneous pressurization system allows conventional tanks to be used.
+			specLevel = prototype
+			minThrust = 26.67
+			maxThrust = 26.67
+			heatProduction = 100
+			
+			PROPELLANT
+			{
+				name = LqdHydrogen
+				ratio = 0.7631
+				DrawGauge = True
+			}
+			
+			PROPELLANT
+			{
+				name = LqdOxygen
+				ratio = 0.2369
+			}
+			//No pressurant, used "VaPak" autogeneous pressurization system
+			
+			ullage = True
+			pressureFed = False		//At 40 psi chamber pressure, this could use mostly normal tanks
+			ignitions = 9
+
+			IGNITOR_RESOURCE
+			{
+				name = ElectricCharge
+				amount = 0.2
+			}
+			
+			atmosphereCurve
+			{
+				key = 0 433
+				key = 0.355 1
+			}
+			
+			massMult = 0.81
+
+			TESTFLIGHT:NEEDS[TestLite|TestFlight]
+			{
+				ratedBurnTime = 450
+				ignitionReliabilityStart = 0.96
+				ignitionReliabilityEnd = 0.9965
+				cycleReliabilityStart = 0.94
+				cycleReliabilityEnd = 0.998		//Reliable but not incredibly so 4 were used for a reason
+			}
+		}
+		
 		CONFIG
 		{
 			name = AJ10-133-LH
@@ -367,6 +440,7 @@
 				ignitionReliabilityEnd = 0.9965
 				cycleReliabilityStart = 0.94
 				cycleReliabilityEnd = 0.998		//Reliable but not incredibly so 4 were used for a reason
+				techTransfer = AJ10-133-Hylas:50
 			}
 		}
 	}