Merlin 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 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 ...
. They are currently a part 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 ...
launch vehicles, and were formerly used on the
Falcon 1. Merlin engines use
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
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 ...
as
rocket propellant
Rocket propellant is used as reaction mass ejected from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.
Overvi ...
s in a
gas-generator power cycle. The Merlin engine was originally designed for sea recovery and reuse, but since 2016 the entire Falcon 9 booster is recovered for reuse by landing vertically on a landing pad using one of its nine Merlin engines.
The injector at the heart of Merlin is of the
pintle type that was first used in the
Apollo Lunar Module
The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed sp ...
landing engine (
LMDE). Propellants are fed by a single-shaft, dual-
impeller
An impeller, or impellor, is a driven rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
Strictly speaking, propellers are a sub-clas ...
turbopump
A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...
. The turbopump also provides high-pressure fluid for the hydraulic
actuator
An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an ...
s, which then recycles into the low-pressure inlet. This eliminates the need for a separate
hydraulic drive system and means that
thrust vectoring
Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to Aircraft flight control system, control the Spacecra ...
control failure by running out of
hydraulic fluid
A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backho ...
is not possible.
Revisions
Merlin 1A
The initial version, the Merlin 1A, used an inexpensive, expendable,
ablatively cooled carbon-fiber-reinforced polymer
Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers ( Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon comp ...
composite nozzle and produced of thrust.
The Merlin 1A flew only twice: first on March 24, 2006, when it caught fire and failed due to a fuel leak shortly after launch,
and the second time on March 21, 2007, when it performed successfully.
Both times the Merlin 1A was mounted on a
Falcon 1
Falcon 1 was a two-stage small-lift launch vehicle that was operated from 2006 to 2009 by SpaceX, an American aerospace manufacturer. On September 28, 2008, Falcon 1 became the first private spaceflight, privately developed fully liquid-fueled l ...
first stage.
The SpaceX turbopump was an entirely new, clean-sheet design contracted to Barber-Nichols, Inc. in 2002, who performed all design, engineering analysis, and construction; the company had previously worked on turbopumps for the
RS-88
The RS-88 (Rocket System-88) is a liquid-fueled rocket engine designed and built in the United States by Rocketdyne (later Pratt & Whitney Rocketdyne and then Aerojet Rocketdyne). Originally developed for NASA's Bantam System Technology program in ...
(Bantam) and NASA
Fastrac engine programs. The Merlin 1A turbopump used a unique
friction-welded main shaft, with
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 ...
718 ends and an integral aluminum RP-1 impeller in the middle. The turbopump housing was constructed using
investment casting
Investment casting is an industrial process based on lost-wax casting, one of the oldest known metal-forming techniques. The term "lost-wax casting" can also refer to modern investment casting processes.
Investment casting has been used in vari ...
s, with Inconel at the turbine end, aluminum in the center, and 300-series stainless steel at the LOX end. The turbine was a partial-admission (i.e., working fluid is only admitted through part of the rotation of the turbine; an arc, not the whole circumference) impulse design and turned at up to 20,000 rpm, with a total weight of .
Merlin 1B
The Merlin 1B rocket engine was an upgraded version of the Merlin 1A engine. The turbopump upgrades were handled by Barber-Nichols, Inc. for SpaceX.
It was intended for
Falcon 1
Falcon 1 was a two-stage small-lift launch vehicle that was operated from 2006 to 2009 by SpaceX, an American aerospace manufacturer. On September 28, 2008, Falcon 1 became the first private spaceflight, privately developed fully liquid-fueled l ...
launch vehicles, capable of producing of thrust at sea level and in vacuum, and performing with a specific impulse of at sea level and in vacuum.
The Merlin 1B was enhanced over the 1A with a
turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...
upgrade, increasing power output from to .
The turbine upgrade was accomplished by adding additional nozzles, turning the previously partial-admission design to full admission. Slightly enlarged impellers for both RP-1 and LOX were part of the upgrade. This model turned at a faster 22,000 rpm and developed higher discharge pressures. Turbopump weight was unchanged at .
Another notable change over the 1A was the move to
TEA
Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of '' Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of south-western China and nor ...
–
TEB (
pyrophoric
A substance is pyrophoric (from , , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolithium compounds and triethylb ...
) ignition over torch ignition.
Initial use of the Merlin 1B was to be on the
Falcon 9 launch vehicle, on whose first stage there would have been a cluster of nine of these engines. Due to experience from the Falcon 1's first flight, SpaceX moved its Merlin development to the Merlin 1C, which is regeneratively cooled. Therefore, the Merlin 1B was never used on a launch vehicle.
Merlin 1C

Three versions of the Merlin 1C engine were produced. The Merlin engine for Falcon 1 had a movable turbopump exhaust assembly, which was used to provide roll control by vectoring the exhaust. The Merlin 1C engine for the Falcon 9 first stage is nearly identical to the variant used for the Falcon 1, although the turbopump exhaust assembly is not movable. Finally, a Merlin 1C
vacuum
A vacuum (: vacuums or vacua) is space devoid of matter. The word is derived from the Latin adjective (neuter ) meaning "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressur ...
variant is used on the Falcon 9 second stage. This engine differs from the Falcon 9 first-stage variant in that it uses a larger exhaust nozzle optimized for vacuum operation and can be throttled between 60% and 100%.
The Merlin 1C uses a
regeneratively cooled nozzle and combustion chamber. The turbopump used is a Merlin 1B model with only slight alterations. It was fired with a full mission duty firing of 170 seconds in November 2007,
first flew on a
mission in August 2008,
powered the "first
developed liquid-fueled rocket to successfully reach orbit",
Falcon 1 Flight 4, in September 2008,
and powered the
Falcon 9 on its maiden flight in June 2010.
As configured for use on Falcon 1 vehicles, the Merlin 1C had a sea-level thrust of , a vacuum thrust of and a vacuum
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), ...
of . In this configuration, the engine consumed of propellant per second. Tests have been conducted with a single Merlin 1C engine successfully running a total of 27 minutes (counting together the duration of the various tests), which equals ten complete
Falcon 1
Falcon 1 was a two-stage small-lift launch vehicle that was operated from 2006 to 2009 by SpaceX, an American aerospace manufacturer. On September 28, 2008, Falcon 1 became the first private spaceflight, privately developed fully liquid-fueled l ...
flights.
The Merlin 1C chamber and nozzle are cooled
regeneratively by per second of kerosene flow and are able to absorb of
heat energy.
A Merlin 1C was first used as part of the unsuccessful third attempt to launch a Falcon 1. In discussing the failure, Elon Musk noted: "The flight of our first stage, with the new Merlin 1C engine that will be used in Falcon 9, was picture perfect."
The Merlin 1C was used in the successful
fourth flight of Falcon 1 on September 28, 2008.
On October 7, 2012, a Merlin 1C (Engine No. 1) of the
CRS-1 mission experienced an
anomaly at T+00:01:20, which appears o
CRS-1 launch videoas a flash. The failure occurred just as the vehicle achieved max-Q (maximum aerodynamic pressure). SpaceX's internal review found that the engine was shut down after a sudden pressure loss and that only the aerodynamic shell was destroyed, generating the debris seen in the video; the engine did not explode, as SpaceX ground control continued to receive data from it throughout the flight. The primary mission was unaffected by the anomaly due to the nominal operation of the remaining eight engines and an onboard readjustment of the flight trajectory,
but the secondary-mission payload failed to reach its target orbit due to safety protocols in place to prevent collisions with the ISS. These protocols prevented a second firing of the upper stage for the secondary payload.
SpaceX was planning to develop a version of Merlin 1C to be used in Falcon 9 Block II and Falcon 1E boosters.
This engine and these booster models were dropped in favor of the more advanced Merlin 1D engine and longer Falcon 9 v1.1 booster.
Merlin Vacuum (1C)
On March 10, 2009, a SpaceX press release announced successful testing of the Merlin Vacuum engine. A variant of the 1C engine, Merlin Vacuum features a larger exhaust section and a significantly larger expansion nozzle to maximize the engine's efficiency in the vacuum of space. Its combustion chamber is
regeneratively cooled, while the
niobium alloy expansion nozzle is
radiatively cooled. The engine delivers a vacuum thrust of and a vacuum
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), ...
of .
The first production Merlin Vacuum engine underwent a full-duration orbital-insertion firing (329 seconds) of the integrated Falcon 9 second stage on January 2, 2010.
It was flown on the second stage for the inaugural Falcon 9 flight on June 4, 2010. At full power and as of March 10, 2009, the Merlin Vacuum engine operates with the greatest efficiency of any American-made hydrocarbon-fueled rocket engine.
An unplanned test of a modified Merlin Vacuum engine was made in December 2010. Shortly before the scheduled
second flight of the
Falcon 9, two cracks were discovered in the niobium-alloy-sheet nozzle of the Merlin Vacuum engine. The engineering solution was to cut off the lower of the nozzle and launch two days later, as the extra performance that would have been gained from the longer nozzle was not necessary to meet the objectives of the mission. The modified engine successfully placed the second stage into an orbit of altitude.
Merlin 1D
The Merlin 1D engine was developed by SpaceX between 2011 and 2012, with first flight in 2013. The design goals for the new engine included increased reliability, improved performance, and improved manufacturability.
In 2011, performance goals for the engine were a vacuum thrust of , a vacuum specific impulse (''I''
sp) of , an expansion ratio of 16 (as opposed to the previous 14.5 of the Merlin 1C) and chamber pressure in the "sweet spot" of . Merlin 1D was originally designed to throttle between 100% and 70% of maximal thrust; however, further refinements since 2013 now allow the engine to throttle to 40%.
The basic Merlin fuel/oxidizer mixture ratio is controlled by the sizing of the propellant supply tubes to each engine, with only a small amount of the total flow trimmed out by a "
servo-motor-controlled butterfly valve
A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates.
Principle of operation
Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves ...
" to provide
fine control of the mixture ratio.
On November 24, 2013, Elon Musk stated that the engine was actually operating at 85% of its potential, and they anticipated to be able to increase the sea-level thrust to about and a thrust-to-weight ratio of 180.
[ Als]
at SoundCloud
. This version of the Merlin 1D was used on
Falcon 9 Full Thrust and first flew on
Flight 20.
In May 2016, SpaceX announced plans to further upgrade the Merlin 1D by increasing vacuum thrust to and sea-level thrust to ; according to SpaceX, the additional thrust will increase the Falcon 9 LEO payload capability to about 22 metric tons on a fully expendable mission. SpaceX also noted that unlike the previous Full Thrust iteration of the Falcon 9 vehicle, the increase in performance is solely due to upgraded engines, and no other significant changes to the vehicle are publicly planned.
In May 2018, ahead of the first flight of
Falcon 9 Block 5, SpaceX announced that the goal had been achieved.
The Merlin 1D is now close to the sea-level thrust of the retired
Rocketdyne H-1
The Rocketdyne H-1 was a thrust liquid-propellant rocket engine burning LOX and RP-1. The H-1 was developed for use in the S-I and S-IB first stages of the Saturn I (rocket), Saturn I and Saturn IB rockets, respectively, where it was used in c ...
/
RS-27
The RS-27 (Rocket System-27) was a liquid-propellant rocket engine developed in 1974 by Rocketdyne to replace the aging Rocketdyne S-3D, MB-3 in the Delta. Incorporating components of the venerable MB-3 and the Rocketdyne H-1, H-1 designs, the ...
engines used on
Saturn I
The Saturn I was a rocket designed as the United States' first medium lift launch vehicle for up to low Earth orbit Payload (air and space craft), payloads.Terminology has changed since the 1960s; back then, 20,000 pounds was considered "heavy l ...
,
Saturn IB
The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43,3 ...
, and
Delta II
Delta II was an expendable launch system, originally designed and built by McDonnell Douglas, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...
.
On February 23, 2024, one of the nine Merlin engines powering that launch flew its 22nd mission, which was at the time the flight leading engine. It is already the most flown rocket engine to date, surpassing
Space Shuttle Main Engine
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 ...
no. 2019's record of 19 flights.
Anomalies
The March 18, 2020, launch of
Starlink
Starlink is a satellite internet constellation operated by Starlink Services, LLC, an international telecommunications provider that is a wholly owned subsidiary of American aerospace company SpaceX, providing coverage to around 130 countries ...
satellites on board a
Falcon 9 experienced an early engine shutdown on ascent. The shutdown occurred 2 minutes 22 seconds into the flight and was accompanied with an "event" seen on camera. The rest of the Falcon 9 engines burned longer and did deliver the payload to orbit. However, the first stage was not successfully recovered. In a subsequent investigation SpaceX found that
isopropyl alcohol
Isopropyl alcohol (IUPAC name propan-2-ol and also called isopropanol or 2-propanol) is a colorless, flammable, organic compound with a pungent alcoholic odor.
Isopropyl alcohol, an organic polar molecule, is miscible in water, ethanol, an ...
, used as cleaning fluid, was trapped and ignited, causing the engine to be shut down. To address the issue, in a following launch SpaceX indicated that the cleaning process was not done.
On October 2, 2020, the launch of a GPS-III satellite was aborted at T-2 seconds due to a detected early startup on 2 of the 9 engines on the first stage. The engines were removed for further testing and it was found that a port in the gas generator was blocked. After removing the blockage the engines started as intended. After this, SpaceX inspected other engines across its fleet and found that two of the engines on the Falcon 9 rocket intended for the Crew-1 launch also had this problem. Those engines were replaced with new M1D engines.
On February 16, 2021, on Falcon 9 flight 108 launching
Starlink
Starlink is a satellite internet constellation operated by Starlink Services, LLC, an international telecommunications provider that is a wholly owned subsidiary of American aerospace company SpaceX, providing coverage to around 130 countries ...
satellites, an engine shut down early due to hot exhaust gasses passing through a damaged heat-shielding cover. The mission was a success, but the booster could not be recovered.
Merlin 1D Vacuum
A vacuum version of the Merlin 1D engine was developed for the
Falcon 9 v1.1 and the
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 ...
second stage.
As of 2020, the thrust of the Merlin 1D Vacuum is
with a specific impulse of 348 seconds,
the highest specific impulse ever for a U.S. hydrocarbon rocket engine.
The increase is due to the greater
expansion ratio The expansion ratio of a liquefied and cryogenic substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at room temperature and normal atmospheric pressure ...
afforded by operating in vacuum, now 165:1 using an updated nozzle extension.
The engine can throttle down to 39% of its maximum thrust, or .
Merlin 1D Vacuum improvements and variants
Transporter-7 mission launch debuted a new Merlin Vacuum engine (MVac for short) nozzle extension design or variant aimed at increasing cadence and reducing costs. This new nozzle extension is shorter and, as a result, decreases both performance and material usage. This nozzle is only used on lower-performance missions, as with this nozzle, the MVac engine produces 10% less thrust in space. The nozzle decreases the amount of material needed by 75%; this means that SpaceX can launch over three times as many missions with the same amount of rare
niobium
Niobium is a chemical element; it has chemical symbol, symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and Ductility, ductile transition metal. Pure niobium has a Mohs scale of mineral hardness, Mohs h ...
metal as with the longer design.
Anomalies
On July 11, 2024, Falcon 9 flight 354 launching
Starlink
Starlink is a satellite internet constellation operated by Starlink Services, LLC, an international telecommunications provider that is a wholly owned subsidiary of American aerospace company SpaceX, providing coverage to around 130 countries ...
group 9-3 from Vandenberg AFB in California experienced an anomaly with its MVac during an engine relight attempt to raise the
perigee
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values.
Apsides perta ...
of the 22 Starlink satellites for deployment. On X, Elon Musk and SpaceX both confirmed the engine failed explosively during a second attempted relight, albeit in a manner that did not appear to damage the second stage of the vehicle as the stage went on to deploy the satellites on board.
Design
Engine control
SpaceX uses a triple-redundant design in the Merlin engine computers. The system uses three computers in each processing unit, each constantly checking on the others, to instantiate a
fault-tolerant design
Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems.
Fault to ...
. One processing unit is part of each of the ten Merlin engines (nine on the first stage, one on the second stage) used on the Falcon 9 launch vehicle.
Turbopump
The Merlin LOX/RP-1
turbopump
A turbopump is a fluid pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The most co ...
used on Merlin engines 1A–1C was designed and developed by Barber-Nichols.
It spins at 36,000
revolutions per minute
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines.
One revolution per minute is equivalent to hertz.
Standards
ISO 80000-3:2019 de ...
, delivering .
Gas generator
The LOX/RP-1 turbopump on each Merlin engine is powered by a fuel-rich open-cycle
gas generator
A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical.
The term often refers to a device that uses a ...
similar to that used in the Apollo-era
Rocketdyne F-1
The F-1 is a rocket engine developed by Rocketdyne. The engine uses a gas-generator cycle developed in the United States in the late 1950s and was used in the Saturn V rocket in the 1960s and early 1970s. Five F-1 engines were used in the S ...
engine.
[Sutton, “History of Liquid Propellant Rocket Engines”, AIAA ]006
Alec Trevelyan is a fictional character who is the main antagonist in the 1995 James Bond film ''GoldenEye,'' portrayed by actor Sean Bean. Bean's likeness was also used as the model for Alec Trevelyan in the 1997 video game '' GoldenEye 007' ...
Production
, SpaceX was producing Merlin engines at the rate of eight per month, planning eventually to raise production to about 33 engines per month (or 400 per year).
By September 2013, SpaceX total manufacturing space had increased to nearly , and the factory had been configured to achieve a maximum production rate of up to 40 rocket cores per year, enough to use the 400 annual engines envisioned by the earlier engine plan.
By October 2014, SpaceX announced that it had manufactured the 100th Merlin 1D engine and that engines were now being produced at a rate of four per week, soon to be increased to five.
In February 2016, SpaceX indicated that the company will need to build hundreds of engines a year in order to support a Falcon 9/Falcon Heavy build rate of 30 rocket cores per year by the end of 2016.
Each Falcon 9 booster uses nine Merlin engines, and the second stage uses one Merlin vacuum engine. The second stage is expended, so each launch consumes one Merlin Vacuum engine. SpaceX designed the booster with its engines to be recovered for reuse by propulsive landing, and the first recovered booster was reused in March 2017. By 2020, only five of the 26 Falcon 9 launched that year used new boosters. By 2021, only two of the 31 Falcon 9 launches used new boosters.
Past engine concepts
Merlin 2 concept
At the
American Institute of Aeronautics and Astronautics
The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering
Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecra ...
Joint Propulsion conference on July 30, 2010, SpaceX McGregor rocket development facility director
Tom Markusic shared some information from the initial stages of planning for a new engine. SpaceX’s Merlin 2
LOX/RP-1-fueled engine on a
gas-generator cycle
The gas-generator cycle, also referred to as the GG cycle or colloquially as an open cycle, is one of the most commonly used power cycles in bipropellant liquid rocket engines.
Propellant is burned in a gas generator (analogous to, but distinct ...
, capable of a projected of thrust at sea level and in a vacuum and would provide the power for conceptual super-heavy-lift launch vehicles from SpaceX, which Markusic dubbed
Falcon X
Before settling on the 2018 SpaceX Starship, 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, ...
and
Falcon XX
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 ...
. Such a capability, if built, would have resulted in an engine with more thrust than the
F-1 engines used on the
Saturn V
The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...
.
Conceived to be potentially used on more capable variants of the Falcon 9 Heavy, Markusic indicated that the Merlin 2 "could be qualified in three years for $1 billion".
By mid-August, SpaceX CEO
Elon Musk
Elon Reeve Musk ( ; born June 28, 1971) is a businessman. He is known for his leadership of Tesla, SpaceX, X (formerly Twitter), and the Department of Government Efficiency (DOGE). Musk has been considered the wealthiest person in th ...
clarified that while the Merlin 2 engine architecture was a key element of any effort SpaceX would make toward their objective of "super-heavy lift" launch vehicles—and that SpaceX did indeed want to "move toward super heavy lift"—the specific potential design configurations of the particular launch vehicles shown by Markusic at the propulsion conference were merely conceptual "brainstorming ideas", just a "bunch of ideas for discussion."
[ ]
Since the original discussion, no work on any "Merlin 2"
kerolox engine has been pursued and made public. At the 2011 Joint Propulsion Conference, Elon Musk stated that SpaceX were instead working towards a potential
staged cycle engine.
In October 2012, SpaceX publicly announced concept work on a rocket engine that would be "several times as powerful as the Merlin 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".
They indicated that the large engine was intended for a new SpaceX rocket, using multiple of these large engines could notionally launch payload masses of the order of to
low-Earth orbit
A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, peaking in number at an ...
. The forthcoming engine currently under development by SpaceX has been named "
Raptor". Raptor will use
liquid methane as a fuel, and was stated as having a sea-level thrust of .
Since the initial announcement of Raptor, Musk has updated the specification to approximately —about one-third the original published figure—based on the results of optimizing for thrust-to-weight ratio.
See also
*
SpaceX Draco – SpaceX
RCS thruster for
SpaceX Dragon
Dragon is a family of spacecraft developed and produced by American private space transportation company SpaceX.
The first variant, later named SpaceX Dragon 1, Dragon 1, flew 23 cargo missions to the International Space Station (ISS) between ...
*
SpaceX Kestrel – SpaceX small upper stage engine for Falcon 1
*
SpaceX Raptor – SpaceX methane/LOX engine for the
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 ...
*
Falcon 1 – First rocket powered by
Merlin 1A
*
Comparison of orbital rocket engines
*
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 ...
*
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 ...
*
TR-106
The TR-106 or low-cost pintle engine (LCPE) was a developmental rocket engine designed by TRW Inc., TRW under the Space Launch Initiative to reduce the cost of Launch service provider, launch services and space flight. Operating on LOX/LH2 the en ...
– Low Cost Pintle Engine (LCPE) using LOX/LH2 developed by TRW in 2000
*
TR-107 – RP-1 engine developed under SLI for future reusable launch vehicles
*
RS-27A
The RS-27 (Rocket System-27) was a liquid-propellant rocket engine developed in 1974 by Rocketdyne to replace the aging MB-3 in the Delta. Incorporating components of the venerable MB-3 and the H-1 designs, the RS-27 was a modernized version ...
– RP-1 engine used in the US
Delta II
Delta II was an expendable launch system, originally designed and built by McDonnell Douglas, and sometimes known as the Thorad Delta 1. Delta II was part of the Delta rocket family, derived directly from the Delta 3000, and entered service in ...
launcher; Saturn 1B
H-1 heritage
*
Rocketdyne F-1
The F-1 is a rocket engine developed by Rocketdyne. The engine uses a gas-generator cycle developed in the United States in the late 1950s and was used in the Saturn V rocket in the 1960s and early 1970s. Five F-1 engines were used in the S ...
– LOX/RP-1 main engine of the
Saturn V
The Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, had multistage rocket, three stages, and was powered by liquid-propel ...
Moon rocket
References
Sources
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External links
SpaceX official website
{{DEFAULTSORT:Merlin (Rocket Engine)
SpaceX rocket engines
Rocket engines using kerosene propellant
Rocket engines using the gas-generator cycle
Rocket engines of the United States