RP-1 (alternatively, Rocket Propellant-1 or Refined Petroleum-1) is a highly refined form of kerosene outwardly similar to jet fuel, used as rocket fuel. RP-1 provides a lower specific impulse than liquid hydrogen (LH2), but is cheaper, is stable at room temperature, and presents a lower explosion hazard. RP-1 is far denser than LH2, giving it a higher energy density (though its specific energy is lower). RP-1 also has a fraction of the toxicity and carcinogenic hazards of hydrazine, another room-temperature liquid fuel.
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