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The Frontier Engine is a high-efficiency but still high-thrust engine that is mainly used for second stages and heavy payloads. It is the second stage counterpart of the Titan Engine and the larger version of the Valiant Engine. This engine is excellent for using it for long interplanetary transfers, since the engine has low fuel consumption.

Since it can be mounted on a 4 unit wide fuel tank, it is sometimes used as a high-efficiency replacement for the Hawk Engine, and can be used in a high stage and fed fuel by lower stages, reducing weight by only requiring a single engine. It has the second highest efficiency after the Ion Engine. It burns through 5t of fuel in 12 seconds.


  • This engine most likely represents the RS-25 SSME, Rocketdyne J-2, or the Rocketdyne J-2X.
  • This engine is more efficient than the Hawk Engine but it has lesser thrust.
  • Prior to 1.35, the Frontier Engine had a rather unique texture.
  • This engine likely burns hydrolox (liquid hydrogen and liquid oxygen), because hydrolox powered engines give off a transparent flame.
  • In real life, the Frontier Engine would probably only be efficient in a vacuum, because rocket engines with a long nozzle and high nozzle ratio are more powerful and efficient in a vacuum, but provide less thrust and efficiency in denser atmospheres.
  • Two clipped frontier engines can be used in a first stage of a rocket in place of Hawk and Titan engines, but they have half the thrust of one Titan Engine. It can also be used for interplanetary transfers that need a lot of fuel to work on.
  • As said in the description, it is a low thrust engine, but it has actually still high thrust.


Basics ParachuteCapsuleHawk EngineValiant EngineKolibri EngineFuel TanksSeparatorSide SeparatorAerodynamic Nose ConeLanding Leg
6 Wide 6 Wide Aerodynamic Nose ConeFuel TanksTitan EngineSeparator
8 Wide 8 Wide Aerodynamic Nose ConeFuel TanksSeparator
10 Wide Fuel TanksSeparator
12 Wide Fuel TanksSeparator
Engines Hawk EngineValiant EngineKolibri EngineTitan EngineFrontier EngineRCS ThrustersIon Engine
Aerodynamic Parts ParachuteSide ParachuteAerodynamic Nose ConeAerodynamic Fuselage
Fairings Fairing
Structural Structural Part
Other Docking PortLanding LegsIon EngineProbeRCS ThrustersRover WheelsSolar Panel
Currently discontinued in Version 1.5
BatteryRadioisotope Thermoelectric Generator