// PROPULSION SYSTEMS AND ENGINE TECHNOLOGY TERM

RP-1

RP-1 is a highly refined form of kerosene, similar to jet fuel, that is widely used as a rocket propellant. It is typically combined with liquid oxygen to power the first stages of launch vehicles like the Falcon 9 and Saturn V.

TECHNICAL DEFINITION

RP-1 (Rocket Propellant-1) is a high-performance, kerosene-based hydrocarbon rocket fuel conforming to military specification MIL-DTL-25576, used in bipropellant liquid rocket engines. It is typically paired with a Liquid Oxygen (LOX) oxidizer, offering a high thrust-to-weight ratio and density, making it ideal for the first stages of launch vehicles such as the SpaceX Falcon 9, Saturn V, and Soyuz.

BACKGROUND

Firefly Aerospace, Inc. (Firefly) is an American aerospace firm based in Cedar Park, Texas. Firefly develops small- and medium-lift launch vehicles for commercial launches to orbit. Firefly's stated purpose is to increase access to space, similar to other private spaceflight companies.

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SYNONYMS & ALIASES

  • Refined Petroleum-1
  • Rocket Propellant-1
  • Kerosene propellant
  • MIL-DTL-25576
  • Hydrocarbon fuel
  • KeroLOX fuel

USAGE NOTE

RP-1 is a popular choice for the first stages of orbital rockets because its high density allows for smaller, lighter fuel tanks compared to liquid hydrogen.

DEVELOPERS

Organizations developing technology related to RP-1.

  • SpaceX

    Develops and operates the Merlin engine family, which powers the Falcon 9 and Falcon Heavy rockets using a sub-cooled version of RP-1, known as RP-1, and liquid oxygen (LOX).

  • Aerojet Rocketdyne

    An L3Harris Technologies company with a long history of developing RP-1 engines, including the historic F-1 for the Saturn V. They developed the modern AR1, an oxygen-rich staged-combustion RP-1 engine.

  • United Launch Alliance (ULA)

    Operates the Atlas V launch vehicle, whose first stage is powered by the Russian-made RD-180 engine, which burns RP-1 and liquid oxygen.

  • Firefly Aerospace

    Designs and manufactures the Reaver engine, which uses RP-1 and LOX to power the first stage of their Alpha launch vehicle.

  • Ursa Major Technologies

    A dedicated rocket engine manufacturer that produces the Hadley engine, a 5,000-pound-thrust, oxygen-rich staged combustion engine designed to run on RP-1 or other kerosene-based fuels.

  • ABL Space Systems

    Develops the RS1 small-satellite launch vehicle, which is powered by nine of their E2 gas-generator cycle engines on the first stage, burning RP-1 and liquid oxygen.

  • NPO Energomash

    A Russian rocket engine manufacturer that designs and produces some of the world's most advanced RP-1 engines, including the RD-180 used on the Atlas V and the RD-181 used on the Antares rocket.

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