Liquid fuel

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Liquid fuel
Density 5 kg/l
Transferable Yes
Tweakable Yes
Drainable Yes
Flow mode Adjacent
Cost 0.8 Funds/l
0.16 Funds/kg
Since version 0.18

Liquid fuel, sometimes called jet fuel, is a resource used to power an engine, used either in conjunction with oxidizer, or intake air, depending on the engine type. It is stored in liquid fuel tanks or fuselages. Because jet engines use this fuel too, it is sometimes called jet fuel, but there is no difference between both fuels.

Associated container and engine types

Rocket fuel tanks contain both liquid fuel and oxidizer, while fuselages contain only liquid fuel. Rocket engines using liquid fuel and oxidizer, use a volumetric mixture of 9 units of liquid fuel per 11 units of oxidizer. All rocket fuel tanks store liquid fuel and oxidizer in this ratio. Jet engines use intake air in a volumetric mixture of 1 unit of liquid fuel per 15 units of intake air. Because all three resources have the same density, the volumetric ratio is also the mass ratio.

Flow and transfer

Liquid fuel's flow mode is adjacent. With the use of an FTX-2 External Fuel Duct non-adjacent tanks can be linked. Even without a fuel duct it is still possible to transfer fuel between them manually.

Since 1.9, liquid fuel can also be drained from tanks using the FTE-1 Drain Valve.

Real world equivalent

Although the official equivalent is unknown, some compare liquid fuel to RP-1, a kerosene usually used in the first stages of a rocket. Both RP-1 and liquid fuel can be stored at room temperature without boiling off. But the mass mixture ratio of RP-1 and liquid oxygen, the common oxidizer for RP-1, is usually above 2 units of oxidizer per unit of RP-1 higher than the 1.22 for liquid fuel and oxidizer.[1][2]

See also


  • Resource is now drainable
  • Added display name
  • Added abbreviation (used in KerbNet)
  • Added volume
  • Added hsp value (heat capacity)
  • Added cost
  • Resource is now tweakable in the VAB/SPH
  • Initial release


  1. Russian/Ukrainian space-rocket and missile liquid-propellant engines
  2. U.S. space-rocket liquid propellant engines