Raptor Vacuum Engine
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Raptor is a family of
rocket engine A rocket engine is a reaction engine, producing thrust in accordance with Newton's third law by ejecting reaction mass rearward, usually a high-speed Jet (fluid), jet of high-temperature gas produced by the combustion of rocket propellants stor ...
s developed and manufactured by
SpaceX Space Exploration Technologies Corp., commonly referred to as SpaceX, is an America, American space technology company headquartered at the SpaceX Starbase, Starbase development site in Starbase, Texas. Since its founding in 2002, the compa ...
. It is the third rocket engine in history designed with a
full-flow staged combustion The staged combustion cycle (sometimes known as topping cycle, preburner cycle, or closed cycle) is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thu ...
fuel cycle, and the first such engine to power a vehicle in flight. The engine is powered by
cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...
liquid methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth make ...
and
liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...
, a combination known as
methalox The highest specific impulse chemical rockets use liquid propellants (liquid-propellant rockets). They can consist of a single chemical (a monopropellant) or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into ...
. SpaceX's super-heavy-lift
Starship A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for interstellar travel, traveling between planetary systems. The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 1 ...
uses Raptor engines in its Super Heavy booster and in the Starship second stage. Starship missions include lifting payloads to Earth orbit and is also planned for missions to the
Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
and
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
. The engines are being designed for reuse with little maintenance.


Design

Raptor is designed for extreme reliability, aiming to support the airline-level safety required by the point-to-point Earth transportation market.
Gwynne Shotwell Gwynne Shotwell ( Rowley, previously Gurevich; born November 23, 1963) is an American businesswoman and engineer. She is the president and chief operating officer of SpaceX, an American space transportation company, where she is responsible fo ...
claimed that Raptor would be able to deliver "long life... and more benign turbine environments".


Full-flow staged combustion

Raptor is powered by subcooled
liquid methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth make ...
and subcooled
liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...
in a
full-flow staged combustion The staged combustion cycle (sometimes known as topping cycle, preburner cycle, or closed cycle) is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thu ...
cycle. This type of combustion is a twin-shaft staged combustion cycle that uses both oxidizer-rich and fuel-rich preburners. The cycle allows for the full flow of both propellants through the turbines without dumping any unburnt propellant overboard. Full-flow staged combustion is a departure from the more traditional "open-cycle" gas generator system and LOX/kerosene propellants used by its predecessor
Merlin The Multi-Element Radio Linked Interferometer Network (MERLIN) is an interferometer array of radio telescopes spread across England. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of UK Re ...
. Before Raptor, no full-flow staged combustion engine had ever been used inflight and only two designs had progressed sufficiently to reach test stands: the Soviet
RD-270 RD-270 (, GRAU index: 8D420) was a single-chamber liquid-fuel rocket engine designed by Energomash (USSR) in 1960–1970. It was to be used on the first stages of the proposed heavy-lift UR-700 and UR-900 rocket families, as well as on the N1 ...
project in the 1960s, a full scale test engine and the
Aerojet Rocketdyne Aerojet Rocketdyne is a subsidiary of American Arms industry, defense company L3Harris that manufactures rocket, Hypersonic flight, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Aerojet traces ...
Integrated Powerhead Demonstrator The integrated powerhead demonstrator (IPD) was a U.S. Air Force project in the 1990s and early 2000s run by NASA and the Air Force Research Laboratory (AFRL) to develop a new rocket engine front-end ("powerhead", sometimes also termed a powerpac ...
in the mid-2000s, which only demonstrated the powerhead.
RS-25 The RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is used on the Space Launch System. Designed and manufactured in the United States by Rocketd ...
engines (first used on the
Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...
) used a simpler form of staged combustion cycle. Several Russian rocket engines, including the
RD-180 The RD-180 () is a rocket engine that was designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/ LOX mixture. The RD-180 is derived from the RD-170 line of rocket engines, which were use ...
and the
RD-191 The RD-191 () is a high-performance single-combustion chamber rocket engine, developed in Russia and sold by Roscosmos. It is derived from the RD-180 dual-combustion chamber engine, which itself was derived in turn from the four-chamber RD-170 ...
did as well. Full-flow staged combustion has the advantage that the energy produced by the preburners, and used to power the propellant pumps, is spread among the entire fuel flow, meaning that the preburner exhaust driving the propellant turbopumps is as cool as possible, even cooler than other closed engine cycles that only preburn one propellant. This contributes to a long engine life. In contrast, an open-cycle engine in which the preburner exhaust bypasses the main combustion chamber tries to minimize the amount of propellant fed through the preburner, which is achieved by operating the turbine at its maximum survivable temperature. An oxygen-rich turbine powers an oxygen turbopump, and a fuel-rich turbine powers a methane turbopump. Both oxidizer and fuel streams are converted completely to the
gas phase In the physical sciences, a phase is a region of material that is chemically uniform, physically distinct, and (often) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a ...
before they enter the
combustion chamber A combustion chamber is part of an internal combustion engine in which the air–fuel ratio, fuel/air mix is burned. For steam engines, the term has also been used for an extension of the Firebox (steam engine), firebox which is used to allow a mo ...
. This speeds up mixing and combustion, reducing the size and mass of the required combustion chamber. Torch igniters are used in the preburners. Because of the high temperatures of the preburner exhaust, the main combustion chamber of Raptor 2 has no main igniter, which eliminate the need for Merlin's dedicated, consumable igniter fluid. Raptor 2 uses coaxial swirl injectors to admit propellants to the combustion chamber, rather than Merlin's
pintle injector The pintle injector is a type of propellant injector for a bipropellant rocket engine. Like any other injector, its purpose is to ensure appropriate flow rate and intermixing of the propellants as they are forcibly injected under high pressure into ...
s.


Propellants

Raptor is designed for
deep Deep or The Deep may refer to: Places United States * Deep Creek (Appomattox River tributary), Virginia * Deep Creek (Great Salt Lake), Idaho and Utah * Deep Creek (Mahantango Creek tributary), Pennsylvania * Deep Creek (Mojave River tributary ...
cryogenic In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a univers ...
propellants—fluids cooled to near their
freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
s, rather than their
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding envi ...
s, as is typical for cryogenic rocket engines. Subcooled propellants are denser, increasing propellant mass per volume as well as engine performance.
Specific impulse Specific impulse (usually abbreviated ) is a measure of how efficiently a reaction mass engine, such as a rocket engine, rocket using propellant or a jet engine using fuel, generates thrust. In general, this is a ratio of the ''Impulse (physics), ...
is increased, and the risk of
cavitation Cavitation in fluid mechanics and engineering normally is the phenomenon in which the static pressure of a liquid reduces to below the liquid's vapor pressure, leading to the formation of small vapor-filled cavities in the liquid. When sub ...
at inputs to the turbopumps is reduced due to the higher propellant fuel mass flow rate per unit of power generated. Cavitation (bubbles) reduces fuel flow/pressure and can starve the engine, while eroding turbine blades. The
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...
to
fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
ratio of the engine is approximately 3.8 to 1. Methalox burns relatively cleanly, reducing carbon build-up in the engine. Liquid methane and
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
propellants have been adopted by many companies, such as
Blue Origin Blue Origin Enterprises, L.P. is an American space technology company headquartered in Kent, Washington. The company operates the suborbital New Shepard rocket and the heavy-lift New Glenn rocket. In addition to producing engines for its own ...
with its
BE-4 The BE-4 (Blue Engine 4) is a liquid rocket engine developed by Blue Origin. It uses an oxygen-rich, liquefied natural gas, liquefied methane fuel and operates on a staged combustion cycle. The BE-4 produces of thrust at sea level. Developmen ...
engine, as well as Chinese startup Space Epoch's Longyun-70.


Manufacturing and materials

Many components of early Raptor prototypes were manufactured using
3D printing 3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer ...
, including turbopumps and injectors, increasing the speed of development and testing. The 2016 subscale development engine had 40% (by mass) of its parts manufactured by 3D printing. In 2019, engine manifolds were cast from SpaceX's in-house developed SX300
Inconel Inconel is a nickel-chromium-based superalloy often utilized in extreme environments where components are subjected to high temperature, pressure or Mechanical load, mechanical loads. Inconel alloys are oxidation- and corrosion-resistant. When he ...
superalloy, later improved to SX500.


History


Conception

SpaceX's
Merlin The Multi-Element Radio Linked Interferometer Network (MERLIN) is an interferometer array of radio telescopes spread across England. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of UK Re ...
and
Kestrel The term kestrel (from , derivative from , i.e. ratchet) is the common name given to several species of predatory birds from the falcon genus ''Falco''. Kestrels are most easily distinguished by their typical hunting behaviour which is to hover ...
rocket engines use a
RP-1 RP-1 (Rocket Propellant-1 or Refined Petroleum-1) and similar fuels like RG-1 and T-1 are highly refined kerosene formulations used as rocket fuel. Liquid-fueled rockets that use RP-1 as fuel are known as kerolox rockets. In their engines, RP- ...
and liquid oxygen ("kerolox") combination. Raptor has about triple the thrust of SpaceX's Merlin 1D engine, which powers the
Falcon 9 Falcon 9 is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. The first Falcon 9 launch was on June 4, 2010, an ...
and
Falcon Heavy Falcon Heavy is a super heavy-lift launch vehicle with partial reusability that can carry cargo into Earth orbit and beyond. It is designed, manufactured and launched by American aerospace company SpaceX. The rocket consists of a center core ...
launch vehicles. Raptor was conceived to burn
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
and
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
propellants as of 2009. SpaceX had a few staff working on the Raptor upper-stage engine at a low priority in 2011. In October 2012, SpaceX announced concept work on an engine that would be "several times as powerful as the
Merlin The Multi-Element Radio Linked Interferometer Network (MERLIN) is an interferometer array of radio telescopes spread across England. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of UK Re ...
1 series of engines, and won't use Merlin's
RP-1 RP-1 (Rocket Propellant-1 or Refined Petroleum-1) and similar fuels like RG-1 and T-1 are highly refined kerosene formulations used as rocket fuel. Liquid-fueled rockets that use RP-1 as fuel are known as kerolox rockets. In their engines, RP- ...
fuel".


Development

In November 2012, Musk announced that SpaceX was working on
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
-fueled rocket engines, that Raptor would be methane-based, and that methane would fuel Mars colonization. Because of the presence of
underground water Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit of rock or an unconsolidate ...
and
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
in Mars atmosphere, methane, a simple
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...
, could be synthesized on Mars using the
Sabatier reaction The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures (perhaps ) in the presence of a nickel catalyst. It was di ...
.
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
found in-situ resource production on Mars to be viable for oxygen, water, and methane production. In early 2014 SpaceX confirmed that Raptor would be used for both first and second stages of its next rocket. This held as the design evolved from the
Mars Colonial Transporter Before settling on the 2018 Starship design, SpaceX successively presented a number of reusable super-heavy lift vehicle proposals. These preliminary spacecraft designs were known under various names ('' Mars Colonial Transporter'', ''Interplanetar ...
to the
Interplanetary Transport System Before settling on the 2018 Starship design, SpaceX successively presented a number of reusable super-heavy lift vehicle proposals. These preliminary spacecraft designs were known under various names ('' Mars Colonial Transporter'', '' Interplanet ...
, the
Big Falcon Rocket Before settling on the 2018 Starship design, SpaceX successively presented a number of reusable super-heavy lift vehicle proposals. These preliminary spacecraft designs were known under various names ('' Mars Colonial Transporter'', '' Interplaneta ...
, and ultimately, Starship. The concept evolved from a family of Raptor-designated rocket engines (2012) to focus on the full-size Raptor engine (2014). In January 2016, the US Air Force awarded a development contract to SpaceX to develop a prototype Raptor for use on the
upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...
of
Falcon 9 Falcon 9 is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. The first Falcon 9 launch was on June 4, 2010, an ...
and
Falcon Heavy Falcon Heavy is a super heavy-lift launch vehicle with partial reusability that can carry cargo into Earth orbit and beyond. It is designed, manufactured and launched by American aerospace company SpaceX. The rocket consists of a center core ...
. The first version was intended to operate at a chamber pressure of . 68th annual meeting of the
International Astronautical Congress The International Astronautical Congress (IAC) is an annual meeting of the actors in the discipline of space science. It is hosted by one of the national society members of the International Astronautical Federation (IAF), with the support of ...
in
Adelaide, Australia Adelaide ( , ; ) is the list of Australian capital cities, capital and most populous city of South Australia, as well as the list of cities in Australia by population, fifth-most populous city in Australia. The name "Adelaide" may refer to ei ...
As of July 2022, chamber pressure had reached 300 bars in a test. In April 2024, Musk shared the performance achieved by SpaceX with the Raptor 1 engine (sea level 185 tf, RVac 200 tf) and Raptor 2 engine (sea level 230 tf, RVac 258 tf) along with the target specifications for the upcoming Raptor 3 (sea level 280 tf, RVac 306 tf) and said SpaceX would aim to ultimately achieve over 330 tonnes of thrust on the sea-level booster engines. Raptor 1 and 2 engines require a heat shroud to protect pipes and wiring from the heat of high-velocity atmospheric re-entry, while Raptor 3 is designed so that it does not require an external heat shield.


Testing

Initial
development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...
testing of Raptor components was done at NASA's
Stennis Space Center The John C. Stennis Space Center (SSC) is a NASA rocket testing facility in Hancock County, Mississippi, United States, on the banks of the Pearl River (Mississippi–Louisiana), Pearl River at the Mississippi–Louisiana border. , it is NASA ...
, beginning in April 2014. Testing focused on startup and shutdown procedures, as well as hardware characterization and verification. SpaceX began testing injectors in 2014 and tested an oxygen
preburner The staged combustion cycle (sometimes known as topping cycle, preburner cycle, or closed cycle) is a power cycle of a bipropellant rocket engine. In the staged combustion cycle, propellant flows through multiple combustion chambers, and is thu ...
in 2015. 76 hot-fire tests of the preburner, totaling some 400 seconds of test time, were executed from April-August. By early 2016, SpaceX had constructed an engine test stand at their McGregor test site in central Texas for Raptor testing. The first Raptor was manufactured at the SpaceX Hawthorne facility in California. By August 2016 it was shipped to McGregor for development testing. The engine had thrust. It was the first-ever full-flow staged combustion methalox engine to reach a test stand. A subscale development engine was used for design validation. It was one-third the size of the engine designs that were envisioned for flight vehicles. It featured of chamber pressure, with a thrust of and used the SpaceX-designed SX500 alloy, created to contain hot oxygen gas in the engine at up to . It was tested on a Rocket engine test facility, ground test stand in SpaceX McGregor, McGregor, firing briefly. To eliminate flow separation problems while testing in Earth's atmosphere, the test nozzle expansion ratio was limited to 150. By September 2017, the subscale engine had completed 1200 seconds of firings across 42 tests. SpaceX completed many static fire tests on a vehicle using Raptor 2s, including a 31 engine test (intended to be 33) on 9 February 2023, and a 33 engine test on 25 August 2023. During testing, more than 50 chambers melted, and more than 20 engines exploded. SpaceX completed its SpaceX Starship integrated flight test 1, first integrated flight test of Starship on 20 April 2023. The rocket had 33 Raptor 2 engines, but three of those were shut down before the rocket lifted off from the launch mount. The flight test was terminated after climbing to an altitude of ~39 km over the Gulf of Mexico. Multiple engines were out before the flight termination system (FTS) destroyed the booster and ship. On the SpaceX Starship integrated flight test 2, second integrated flight test all 33 booster engines remained lit until boostback burn startup, and all six Starship engines remained lit until the FTS was activated. On the SpaceX Starship integrated flight test 3, third integrated flight test, all 33 booster engines once again remained lit until main engine cutoff, and then following hot-staging, 13 successfully relit to perform a boostback for full duration. On the booster's landing burn, only 3 engines of the planned 13 lit, with 2 shutting down rapidly, the other remained lit until the booster was destroyed ~462 metres above sea level. The ship successfully kept all 6 engines lit until second stage / secondary engine cutoff without issues, however a planned in-space Raptor re-light was cancelled due to rolling during coast. The Starship flight test 7, seventh flight test featured the first reflown Raptor engine, which was successfully flown during Super Heavy booster 14's ascent burn and was recovered after its successful catch. Booster 14 will be reflown for the first time on Starship's Starship flight test 9, ninth test flight, with 29 out of 33 Raptors from its previous mission accompanying it.


Starship


Original configuration

In November 2016, Raptor was projected to power the proposed
Interplanetary Transport System Before settling on the 2018 Starship design, SpaceX successively presented a number of reusable super-heavy lift vehicle proposals. These preliminary spacecraft designs were known under various names ('' Mars Colonial Transporter'', '' Interplanet ...
(ITS), in the early 2020s. Musk discussed two engines: a sea-level variant (expansion ratio 40:1) with thrust of at sea level for the first stage/booster, and a vacuum variant (expansion ratio 200:1) with thrust of in space. 42 sea-level engines were envisioned in the high-level design of the first stage. Three Gimbal#Rocket engines, gimbaling sea-level Raptor engines would be used for Retropropulsive landing, landing the second stage. Six additional, non-gimbaling vacuum-optimized Raptor Vacuum engines would provide primary thrust for the second stage, for a total of nine engines. Raptor Vacuums were envisioned to contribute a specific impulse of , using a Rocket engine nozzle#Vacuum use, nozzle extension. In September 2017 Musk said that a smaller Raptor engine—with slightly over half as much thrust as the previous designs—would be used on the next-generation rocket, a -diameter launch vehicle termed Big Falcon Rocket (BFR) and later renamed
Starship A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for interstellar travel, traveling between planetary systems. The term is mostly found in science fiction. Reference to a "star-ship" appears as early as 1 ...
. The redesign was aimed at Earth-orbit and Cislunar space, cislunar missions so that the new system might Rate of return, pay for itself, in part, through economic spaceflight activities in the near-Earth space zone. With the much smaller launch vehicle, fewer Raptor engines would be needed. BFR was then slated to have 31 Raptors on the first stage and 6 on the second stage. By mid-2018, SpaceX was publicly stating that the sea-level Raptor was expected to have thrust at sea level with a specific impulse of , with a nozzle exit diameter of . Raptor Vacuum would have specific impulse of in vacuum and was expected to exert force with a specific impulse of , using a nozzle exit diameter of . In the Big Falcon Rocket, BFR update given in September 2018, Musk showed a video of a 71-second fire test of a Raptor engine, and stated that "this is Raptor that will power BFR, both the ship and the booster; it's the same engine. [...] approximately a 200 (metric) tons engine aiming for roughly 300 bar chamber pressure. [...] If you had it at a high expansion ratio, has the potential to have a specific impulse of 380." SpaceX aimed at a lifetime of 1000 flights.


Proposed Falcon 9 upper stage

In January 2016, the US Air Force, United States Air Force (USAF) awarded a development contract to SpaceX to develop a Raptor prototype for use on the
upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...
of the
Falcon 9 Falcon 9 is a Reusable launch system#Partial reusable launch systems, partially reusable, two-stage-to-orbit, medium-lift launch vehicle designed and manufactured in the United States by SpaceX. The first Falcon 9 launch was on June 4, 2010, an ...
and
Falcon Heavy Falcon Heavy is a super heavy-lift launch vehicle with partial reusability that can carry cargo into Earth orbit and beyond. It is designed, manufactured and launched by American aerospace company SpaceX. The rocket consists of a center core ...
. The contract required double-matching funding by SpaceX of at least . Engine testing was planned for NASA's
Stennis Space Center The John C. Stennis Space Center (SSC) is a NASA rocket testing facility in Hancock County, Mississippi, United States, on the banks of the Pearl River (Mississippi–Louisiana), Pearl River at the Mississippi–Louisiana border. , it is NASA ...
in Mississippi under US Air Force supervision. The USAF contract called for a single prototype engine and ground tests. In October 2017 USAF awarded a modification contract for a Raptor prototype for the Evolved Expendable Launch Vehicle program. It was to use
liquid methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth make ...
and
liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...
propellants, a full-flow staged combustion, full-flow staged combustion cycle, and be reusable.


Production

In July 2021, SpaceX announced a second Raptor production facility, in central Texas near the SpaceX McGregor, existing rocket engine test facility. The facility would concentrate on serial production of Raptor 2, while the California facility would produce Raptor Vacuum and new/experimental Raptor designs. The new facility was expected to eventually produce 800 to 1000 rocket engines each year. In 2019 the (marginal) cost of the engine was stated to be approaching . SpaceX planned to mass-produce up to 500 Raptor engines per year, each costing less than .


Versions

Raptor has evolved significantly since it was revealed.


Raptor Vacuum

Each version of the engine has a corresponding Raptor Vacuum (RVac) variant with an extended, Regenerative cooling (rocketry), regeneratively-cooled nozzle for higher specific impulse in space. The vacuum-optimized Raptor targets a specific impulse of ≈. A full-duration test of version 1 of Raptor Vacuum was completed in September 2020 at McGregor. The first in-flight ignition of a Raptor Vacuum was on S25 during the SpaceX Starship integrated flight test 2, second integrated flight test.


Raptor 2

Raptor 2 is a complete redesign of the Raptor 1 engine. The turbomachinery, chamber, nozzle, and electronics were all redesigned. Many flanges were converted to welding, welds, while other parts were deleted. Simplifications continued after production began. On 10 February 2022, Musk showed Raptor 2 capabilities and design improvements. By 18 December 2021, Raptor 2 had started production. By November 2022, SpaceX produced more than one Raptor a day and had created a stockpile for future launches. Raptor 2s are produced at SpaceX's McGregor SpaceX McGregor, engine development facility. Raptor 2s were achieving of thrust consistently by February 2022. Musk indicated that production costs were approximately half that of Raptor 1.


Raptor 3

Raptor 3 is aimed to ultimately achieve of thrust in the booster/sea-level configuration. As of August 2024, it had reached 280 tf. It weighs 1525 kg. Chamber pressure reached . Another goal is to eliminate protective engine shrouds. Raptor 3 moves much of the plumbing and sensors into the housing wall, where integral cooling and integral secondary flow circuits run through various sections of the engine, obviating the need for a separate heat shield. On 2 August 2024, Raptor 3 SN1 was revealed. The reduction in externally visible components was so extreme that the CEO of United Launch Alliance, Tory Bruno, mistakenly accused SpaceX of revealing a "partially assembled" engine while comparing it to fully assembled engines. Many bolted joints in Raptor 2 have been eliminated/replaced by single parts. However, servicing is more difficult, as some parts lie beneath welded joints.


LEET

In October 2021, SpaceX initiated an effort to develop a conceptual design for a new rocket engine with the goal of keeping cost below per ton of thrust. The project was called the 1337 engine, to be pronounced "LEET" (after a Leet, coding meme). Although the initial design effort was halted in late 2021, the project helped define an ideal engine, and likely generated ideas that were incorporated into Raptor 3. Musk stated then that "We can't make life multiplanetary with Raptor, as it is way too expensive, but Raptor is needed to tide us over until 1337 is ready." In June 2024, the LEET concept was clarified as a total tearup of the Raptor 3 design, with Musk stating that SpaceX will "probably do that at some point. ... [Raptor 3] looks like a LEET engine, but its way more expensive because it still has 3D printing, printed parts, for example."


Comparison to other engines


See also

*Comparison of orbital rocket engines *SpaceX Mars program *SpaceX rocket engines *SpaceX Starship (spacecraft) *SpaceX Super Heavy *Starship HLS *SpaceX Starbase


References


External links


SpaceX Raptor Engine Test on 25 September 2016
''SciNews'', video, September 2016.

Adam Lichtl and Steven Jones, GPU Technology Conference, spring 2015.
unofficial Raptor engine log infographic
{{DEFAULTSORT:Raptor Rocket engines using methane propellant SpaceX rocket engines Rocket engines using full flow staged combustion cycle Rocket engines of the United States SpaceX Starship