page_title: SpaceX Raptor
section_title: Description
hierarchical_section_title: SpaceX Raptor / Description
context_page_description: The SpaceX Raptor is a full-flow staged combustion, methane-fueled rocket engine manufactured by SpaceX. The engine is powered by cryogenic liquid methane and liquid oxygen, rather than the RP-1 kerosene and LOX used in SpaceX's prior Merlin and Kestrel rocket engines. The earliest concepts for Raptor considered liquid hydrogen as fuel rather than methane. The Raptor engine has more than two times the thrust of the Merlin 1D engine that powers the current Falcon 9 launch vehicle.
  Raptor will be used in both stages of the two-stage-to-orbit, super heavy-lift launch vehicle Starship.
  The Raptor engine is a highly reusable methalox staged combustion engine that will power the next generation of SpaceX launch vehicles designed to replace all existing SpaceX vehicles, including the Falcon 9 and Falcon Heavy launch vehicles and the SpaceX Dragon 2. Raptor engines are expected to be used in various applications, including existing Earth-orbit satellite delivery market, the exploration and colonization of Mars.
  Raptor engines began flight testing on the Starhopper in July 2019 and became the first full-flow staged combustion rocket engine ever flown.
context_section_description: The Raptor engine is powered by subcooled liquid methane and subcooled liquid oxygen using a more efficient staged combustion cycle, a departure from the simpler "open-cycle" gas generator system and lox/kerosene propellants that current Merlin engines use. The RS-25, with hydrolox propellant also used a staged combustion process, as do several Russian rocket engines, including the RD-180 and the 25.74 MPa (3,733 psi) chamber pressure RD-191. The stated design size for the Raptor engine varied widely during 2012–2017 as detailed design continued, from a high target of 8,200 kN (1,800,000 lbf) of vacuum thrust to a more recent, much lower target of 1,900 kN (430,000 lbf). In its 2017 iteration, the operational engine is expected to have a vacuum Iₛₚ = 382 s (3,750 m/s) and a sea-level Iₛₚ = 334 s (3,280 m/s).
  The Raptor engine is designed for the use of deep cryogenic methalox propellants—fluids cooled to near their freezing points, rather than nearer their boiling points, which is more typical for cryogenic rocket engines. The use of subcooled propellants increases propellant density to allow more propellant mass in tanks; the engine performance is also improved with subcooled propellants. Specific impulse is increased, and the risk of cavitation at inputs to the turbopumps is reduced due to the higher mass flow rate per unit power generated. Engine ignition for all Raptor engines, both on the pad and in the air, will be by spark ignition, which will eliminate the pyrophoric mixture of triethylaluminum-triethylborane (TEA-TEB) used for engine ignition on the Falcon 9 and Falcon Heavy.
  Raptor has been claimed to be able to deliver "long life ... and more benign turbine environments". Specifically, Raptor utilizes a full-flow staged combustion cycle, where all the oxidizer—with a low-fuel ratio—will power the oxygen turbine pump, and all the fuel—with a low-oxygen ratio—will power the methane turbine pump.  Both streams—oxidizer and fuel—will be mixed completely in the gas phase before they enter the combustion chamber.  Prior to 2014, only two full-flow staged-combustion rocket engines had ever progressed sufficiently to be tested on test stands: the Soviet RD-270 project in the 1960s and the Aerojet Rocketdyne Integrated Powerhead Demonstrator in the mid-2000s.
  Additional characteristics of the full-flow design, projected to further increase performance or reliability include:
  eliminating the fuel–oxidizer turbine interseal, which is a potential point of failure in more traditional engine designs;
  lower pressures are required through the pumping system, increasing life span and further reducing risk of catastrophic failure;
  ability to increase the combustion-chamber pressure, thereby either increasing overall performance or "by using cooler gases, providing the same performance as a standard staged combustion engine but with much less stress on materials, thus significantly reducing material fatigue or [engine] weight".
  SpaceX aims at a lifetime of 1000 flights for Raptor.
  The turbopump and many of the critical parts of the injectors for the initial engine development testing were, as of 2015, manufactured by using 3D printing, which increases the speed of development and iterative testing. The 2016 1 MN (220,000 lbf) test-stand engine had 40% (by mass) of its parts manufactured by 3D printing.
  The Raptor engine uses a large number of coaxial swirl injectors to admit propellants to the combustion chamber, rather than pintle injectors used on the previous Merlin rocket engines that SpaceX mass-produced for its Falcon family of launch vehicles.
  Raptor uses "dual redundant torch igniters".
caption: Full-flow staged-combustion rocket engine
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