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SpaceX Merlin

Merlin is a family of rocket engines developed by SpaceX for use on its Falcon 1, Falcon 9 and Falcon Heavy launch vehicles. Merlin engines use RP-1 and liquid oxygen as rocket propellants 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.

Merlin 1D
Test firing of the Merlin 1D at SpaceX’s McGregor test stand
Country of originUnited States
ManufacturerSpaceX
Application
Associated LVFalcon 1, Falcon 9, Falcon Heavy
StatusActive
Liquid-fuel engine
PropellantLOX / RP-1
CycleGas-generator
Performance
Thrust, vacuum981 kN (221,000 lbf)[1]
Thrust, sea-level854 kN (192,000 lbf)[1]
Throttle rangeSea level: 845 to 482 kN (190,000 to 108,300 lbf) (57%)[1]
Vacuum: 981 to 626 kN (220,500 to 140,679 lbf) (64%)[1]
Thrust-to-weight ratio184
Chamber pressure9.7 MPa (1,410 psi)[2]
Specific impulse, vacuum311 s (3.05 km/s)[3] [needs update]
Specific impulse, sea-level282 s (2.77 km/s)[3] [needs update]
Dimensions
DiameterSea level: 0.92 m (3.0 ft)
Vacuum: 3.3 m (11 ft)
Dry weight470 kg (1,030 lb)[4]

The injector at the heart of Merlin is of the pintle type that was first used in the Apollo Lunar Module landing engine (LMDE). Propellants are fed by a single-shaft, dual-impeller turbopump. The turbopump also provides high-pressure fluid for the hydraulic actuators, which then recycles into the low-pressure inlet. This eliminates the need for a separate hydraulic drive system and means that thrust vectoring control failure by running out of hydraulic fluid is not possible.

Revisions

 
SpaceX Merlin 1A

Merlin 1A

The initial version, the Merlin 1A, used an inexpensive, expendable, ablatively cooled carbon-fiber-reinforced polymer composite nozzle and produced 340 kN (76,000 lbf) 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,[5][6] and the second time on March 21, 2007, when it performed successfully.[7] Both times the Merlin 1A was mounted on a Falcon 1 first stage.[8][9]

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 (Bantam) and NASA Fastrac engine programs. The Merlin 1A turbopump used a unique friction-welded main shaft, with Inconel 718 ends and an integral aluminum RP-1 impeller in the middle. The turbopump housing was constructed using investment castings, 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 68 kg (150 lb).[citation needed]

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.[10] It was intended for Falcon 1 launch vehicles, capable of producing 380 kN (85,000 lbf) of thrust at sea level and 420 kN (95,000 lbf) in vacuum, and performing with a specific impulse of 261 s (2.56 km/s) at sea level and 303 s (2.97 km/s) in vacuum.

The Merlin 1B was enhanced over the 1A with a turbine upgrade, increasing power output from 1,500 kW (2,000 hp) to 1,900 kW (2,500 hp).[11] 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 68 kg (150 lb).[10] Another notable change over the 1A was the move to TEATEB (pyrophoric) ignition over torch ignition.[11]

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.[8][9]

Merlin 1C

Merlin 1C
Country of originUnited States
ManufacturerSpaceX
Application
Associated LVFalcon 1, Falcon 9
StatusRetired
Liquid-fuel engine
PropellantLOX / RP-1
CycleGas-generator
Performance
Thrust, vacuum 480 kN (110,000 lbf)[12]
Thrust, sea-level420 kN (94,000 lbf)[12]
Thrust-to-weight ratio96
Chamber pressure6.77 MPa (982 psi)[13]
Specific impulse, vacuum304.8 s (2.99 km/s)[13]
Specific impulse, sea-level275 s (2.70 km/s)
Dimensions
Length2.92 m (9.58 ft)[14]
Dry weight630 kg (1,380 lb)
 
Merlin 1C under construction at SpaceX

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 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%.[13]

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,[12] first flew on a mission in August 2008,[15] powered the "first privately-developed liquid-fueled rocket to successfully reach orbit", Falcon 1 Flight 4, in September 2008,[15] and powered the Falcon 9 on its maiden flight in June 2010.[16]

As configured for use on Falcon 1 vehicles, the Merlin 1C had a sea-level thrust of 350 kN (78,000 lbf), a vacuum thrust of 400 kN (90,000 lbf) and a vacuum specific impulse of 304 s (2.98 km/s). In this configuration, the engine consumed 140 kg (300 lb) 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 flights.[17] The Merlin 1C chamber and nozzle are cooled regeneratively by 45 kg (100 lb) per second of kerosene flow and are able to absorb 10 MW (13,000 hp) of heat energy.[18]

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."[19] The Merlin 1C was used in the successful fourth flight of Falcon 1 on September 28, 2008.[20]

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 on CRS-1 launch video as 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,[21] 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.[22]

SpaceX was planning to develop a 560 kN (130,000 lbf) version of Merlin 1C to be used in Falcon 9 Block II and Falcon 1E boosters.[23] 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 1C Vacuum engine at Hawthorne factory in 2008

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 2.7-meter-long (9 ft)[24] niobium alloy[13] expansion nozzle is radiatively cooled. The engine delivers a vacuum thrust of 411 kN (92,500 lbf) and a vacuum specific impulse of 342 s (3.35 km/s).[25] 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.[26] 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.[27]

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 2.7-meter-long (9 ft) niobium-alloy-sheet nozzle of the Merlin Vacuum engine. The engineering solution was to cut off the lower 1.2 m (4 ft) 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 11,000 km (6,800 mi) altitude.[24]

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.[28] In 2011, performance goals for the engine were a vacuum thrust of 690 kN (155,000 lbf), a vacuum specific impulse (Isp) of 310 s (3.0 km/s), an expansion ratio of 16 (as opposed to the previous 14.5 of the Merlin 1C) and chamber pressure in the "sweet spot" of 9.7 MPa (1,410 psi). 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%.[29]

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" to provide fine control of the mixture ratio.[30]

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 730 kN (165,000 lbf) and a thrust-to-weight ratio of 180.[31] 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 914 kN (205,000 lbf) and sea-level thrust to 845 kN (190,000 lbf); 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 190,000 lbf (850 kN) goal had been achieved.[32] The Merlin 1D is now close to the sea-level thrust of the retired Rocketdyne H-1 / RS-27 engines used on Saturn I, Saturn IB, and Delta II.

Anomalies

The March 18, 2020, launch of Starlink 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, 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.[33][34][35]

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.[36]

On February 16, 2021, on Falcon 9 flight 108 launching Starlink 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.[37]

Merlin 1D Vacuum

A vacuum version of the Merlin 1D engine was developed for the Falcon 9 v1.1 and the Falcon Heavy second stage.[2] As of 2020, the thrust of the Merlin 1D Vacuum is 220,500 lbf (981 kN)[38] with a specific impulse of 348 seconds,[39] the highest specific impulse ever for a U.S. hydrocarbon rocket engine.[40] The increase is due to the greater expansion ratio afforded by operating in vacuum, now 165:1 using an updated nozzle extension.[39][41]

The engine can throttle down to 39% of its maximum thrust, or 360 kN (81,000 lbf).[41]

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. 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.[42]

Turbopump

The Merlin LOX/RP-1 turbopump used on Merlin engines 1A–1C was designed and developed by Barber-Nichols.[43] It spins at 36,000 revolutions per minute, delivering 10,000 horsepower (7,500 kW).[44]

Gas generator

The LOX/RP-1 turbopump on each Merlin engine is powered by a fuel-rich open-cycle gas generator similar to that used in the Apollo-era Rocketdyne F-1 engine.[45]

Production

As of August 2011, 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).[2] By September 2013, SpaceX total manufacturing space had increased to nearly 93,000 square meters (1 million square feet), 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.[46] 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.[47][48]

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.[49][needs update]

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 launches used new boosters. These 26 launches used 25 new Merlin Vacuum engines and 45 new sea-level Merlin engines. By 2021, only two of the 31 Falcon 9 launches used new boosters. In the first half of 2022, there were 27 Falcon 9 launches, two of which used a new booster.

See also

References

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  18. ^ . Updates Archive. SpaceX. December 2007. Archived from the original on April 5, 2013. Retrieved December 27, 2012. (2007:) Merlin has a thrust at sea level of 95,000 lbs, a vacuum thrust of over 108,000 pounds, vacuum specific impulse of 304 seconds and sea level thrust to weight ratio of 92. In generating this thrust, Merlin consumes 350 lbs/second of propellant and the chamber and nozzle, cooled by 100 lbs/sec of kerosene, are capable of absorbing 10 MW of heat energy. A planned turbo pump upgrade in 2009 will improve the thrust by over 20% and the thrust to weight ratio by approximately 25%.
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  30. ^ "Servo Motors Survive Space X Launch Conditions". MICROMO/Faulhabler. 2015. from the original on February 20, 2017. Retrieved August 14, 2015. the fuel-trim valve adjusts the mixture in real time. The fuel-trim device consists of a servo-motor-controlled butterfly valve. To achieve the proper speed and torque, the design incorporates a planetary gearbox for a roughly 151:1 reduction ratio, gearing internal to the unit. The shaft of the motor interfaces with the valve directly to make fine adjustments. 'The basic mixture ratio is given by the sizing of the tubes, and a small amount of the flow of each one gets trimmed out', explains Frefel. 'We only adjust a fraction of the whole fuel flow.'
  31. ^ Elon, Musk (November 24, 2013). . Archived from the original on December 3, 2013. Retrieved November 28, 2013. Also at SoundCloud December 7, 2013, at the Wayback Machine.
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  43. ^ "Merlin LOX/RP-1 Turbopump". website "Products" page: Rocket Engine Turbopumps. Barber-Nichols. from the original on March 13, 2016. Retrieved November 22, 2012.
  44. ^ Musk, Elon (October 13, 2018). "Full Q&A: Tesla and SpaceX CEO Elon Musk on Recode Decode" (offset 01:02:08) (Interview). Interviewed by Kara Swisher. from the original on November 2, 2018. Retrieved November 2, 2018. the turbopump on the Merlin engine runs at 36,000 rpm, it's 10,000 hp
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  48. ^ "SpaceX Prepared Testimony by Jeffrey Thornburg". SpaceRef.com. June 26, 2015. the Merlin engine has now successfully flown to space more than 180 times (with 130 on the Merlin 1D), reliably delivering multiple payloads for U.S, Government and commercial customers to complex orbits. Due to the engine's highly manufacturable design, SpaceX is now producing 4 Merlin 1D engines per week, with current production capacity to produce 5 engines per week, far more than any other private rocket engine producer in the world.
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Sources

  • Belfiore, Michael (January 18, 2005). "Race for Next Space Prize Ignites". Wired.

External links

  • SpaceX official website

spacex, merlin, this, article, about, line, rocket, engines, developed, spacex, line, airplane, engines, also, named, merlin, rolls, royce, merlin, merlin, family, rocket, engines, developed, spacex, falcon, falcon, falcon, heavy, launch, vehicles, merlin, eng. This article is about the line of rocket engines developed by SpaceX For the line of airplane engines also named Merlin see Rolls Royce Merlin Merlin is a family of rocket engines developed by SpaceX for use on its Falcon 1 Falcon 9 and Falcon Heavy launch vehicles Merlin engines use RP 1 and liquid oxygen as rocket propellants 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 Merlin 1DTest firing of the Merlin 1D at SpaceX s McGregor test standCountry of originUnited StatesManufacturerSpaceXApplicationBooster stage engines Upper stage engineAssociated LVFalcon 1 Falcon 9 Falcon HeavyStatusActiveLiquid fuel enginePropellantLOX RP 1CycleGas generatorPerformanceThrust vacuum981 kN 221 000 lbf 1 Thrust sea level854 kN 192 000 lbf 1 Throttle rangeSea level 845 to 482 kN 190 000 to 108 300 lbf 57 1 Vacuum 981 to 626 kN 220 500 to 140 679 lbf 64 1 Thrust to weight ratio184Chamber pressure9 7 MPa 1 410 psi 2 Specific impulse vacuum311 s 3 05 km s 3 needs update Specific impulse sea level282 s 2 77 km s 3 needs update DimensionsDiameterSea level 0 92 m 3 0 ft Vacuum 3 3 m 11 ft Dry weight470 kg 1 030 lb 4 The injector at the heart of Merlin is of the pintle type that was first used in the Apollo Lunar Module landing engine LMDE Propellants are fed by a single shaft dual impeller turbopump The turbopump also provides high pressure fluid for the hydraulic actuators which then recycles into the low pressure inlet This eliminates the need for a separate hydraulic drive system and means that thrust vectoring control failure by running out of hydraulic fluid is not possible Contents 1 Revisions 1 1 Merlin 1A 1 2 Merlin 1B 1 3 Merlin 1C 1 4 Merlin Vacuum 1C 1 5 Merlin 1D 1 5 1 Anomalies 1 6 Merlin 1D Vacuum 2 Design 2 1 Engine control 2 2 Turbopump 2 3 Gas generator 3 Production 4 See also 5 References 5 1 Sources 6 External linksRevisions Edit SpaceX Merlin 1A Merlin 1A Edit The initial version the Merlin 1A used an inexpensive expendable ablatively cooled carbon fiber reinforced polymer composite nozzle and produced 340 kN 76 000 lbf 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 5 6 and the second time on March 21 2007 when it performed successfully 7 Both times the Merlin 1A was mounted on a Falcon 1 first stage 8 9 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 Bantam and NASA Fastrac engine programs The Merlin 1A turbopump used a unique friction welded main shaft with Inconel 718 ends and an integral aluminum RP 1 impeller in the middle The turbopump housing was constructed using investment castings 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 68 kg 150 lb citation needed Merlin 1B Edit 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 10 It was intended for Falcon 1 launch vehicles capable of producing 380 kN 85 000 lbf of thrust at sea level and 420 kN 95 000 lbf in vacuum and performing with a specific impulse of 261 s 2 56 km s at sea level and 303 s 2 97 km s in vacuum The Merlin 1B was enhanced over the 1A with a turbine upgrade increasing power output from 1 500 kW 2 000 hp to 1 900 kW 2 500 hp 11 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 68 kg 150 lb 10 Another notable change over the 1A was the move to TEA TEB pyrophoric ignition over torch ignition 11 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 8 9 Merlin 1C Edit Merlin 1CCountry of originUnited StatesManufacturerSpaceXApplicationBooster stage engines Upper stage engineAssociated LVFalcon 1 Falcon 9StatusRetiredLiquid fuel enginePropellantLOX RP 1CycleGas generatorPerformanceThrust vacuum480 kN 110 000 lbf 12 Thrust sea level420 kN 94 000 lbf 12 Thrust to weight ratio96Chamber pressure6 77 MPa 982 psi 13 Specific impulse vacuum304 8 s 2 99 km s 13 Specific impulse sea level275 s 2 70 km s DimensionsLength2 92 m 9 58 ft 14 Dry weight630 kg 1 380 lb Merlin 1C under construction at SpaceX 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 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 13 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 12 first flew on a mission in August 2008 15 powered the first privately developed liquid fueled rocket to successfully reach orbit Falcon 1 Flight 4 in September 2008 15 and powered the Falcon 9 on its maiden flight in June 2010 16 As configured for use on Falcon 1 vehicles the Merlin 1C had a sea level thrust of 350 kN 78 000 lbf a vacuum thrust of 400 kN 90 000 lbf and a vacuum specific impulse of 304 s 2 98 km s In this configuration the engine consumed 140 kg 300 lb 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 flights 17 The Merlin 1C chamber and nozzle are cooled regeneratively by 45 kg 100 lb per second of kerosene flow and are able to absorb 10 MW 13 000 hp of heat energy 18 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 19 The Merlin 1C was used in the successful fourth flight of Falcon 1 on September 28 2008 20 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 on CRS 1 launch video as 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 21 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 22 SpaceX was planning to develop a 560 kN 130 000 lbf version of Merlin 1C to be used in Falcon 9 Block II and Falcon 1E boosters 23 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 1C Vacuum engine at Hawthorne factory in 2008 Merlin Vacuum 1C Edit 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 2 7 meter long 9 ft 24 niobium alloy 13 expansion nozzle is radiatively cooled The engine delivers a vacuum thrust of 411 kN 92 500 lbf and a vacuum specific impulse of 342 s 3 35 km s 25 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 26 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 27 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 2 7 meter long 9 ft niobium alloy sheet nozzle of the Merlin Vacuum engine The engineering solution was to cut off the lower 1 2 m 4 ft 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 11 000 km 6 800 mi altitude 24 Merlin 1D Edit 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 28 In 2011 performance goals for the engine were a vacuum thrust of 690 kN 155 000 lbf a vacuum specific impulse Isp of 310 s 3 0 km s an expansion ratio of 16 as opposed to the previous 14 5 of the Merlin 1C and chamber pressure in the sweet spot of 9 7 MPa 1 410 psi 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 29 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 to provide fine control of the mixture ratio 30 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 730 kN 165 000 lbf and a thrust to weight ratio of 180 31 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 914 kN 205 000 lbf and sea level thrust to 845 kN 190 000 lbf 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 190 000 lbf 850 kN goal had been achieved 32 The Merlin 1D is now close to the sea level thrust of the retired Rocketdyne H 1 RS 27 engines used on Saturn I Saturn IB and Delta II Anomalies Edit The March 18 2020 launch of Starlink 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 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 33 34 35 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 36 On February 16 2021 on Falcon 9 flight 108 launching Starlink 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 37 Merlin 1D Vacuum Edit A vacuum version of the Merlin 1D engine was developed for the Falcon 9 v1 1 and the Falcon Heavy second stage 2 As of 2020 the thrust of the Merlin 1D Vacuum is 220 500 lbf 981 kN 38 with a specific impulse of 348 seconds 39 the highest specific impulse ever for a U S hydrocarbon rocket engine 40 The increase is due to the greater expansion ratio afforded by operating in vacuum now 165 1 using an updated nozzle extension 39 41 The engine can throttle down to 39 of its maximum thrust or 360 kN 81 000 lbf 41 Design EditEngine control Edit 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 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 42 Turbopump Edit The Merlin LOX RP 1 turbopump used on Merlin engines 1A 1C was designed and developed by Barber Nichols 43 It spins at 36 000 revolutions per minute delivering 10 000 horsepower 7 500 kW 44 Gas generator Edit The LOX RP 1 turbopump on each Merlin engine is powered by a fuel rich open cycle gas generator similar to that used in the Apollo era Rocketdyne F 1 engine 45 Production EditAs of August 2011 update 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 2 By September 2013 SpaceX total manufacturing space had increased to nearly 93 000 square meters 1 million square feet 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 46 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 47 48 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 49 needs update 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 launches used new boosters These 26 launches used 25 new Merlin Vacuum engines and 45 new sea level Merlin engines By 2021 only two of the 31 Falcon 9 launches used new boosters In the first half of 2022 there were 27 Falcon 9 launches two of which used a new booster See also EditSpaceX Draco SpaceX RCS thruster for SpaceX Dragon SpaceX Kestrel SpaceX small upper stage engine for Falcon 1 SpaceX Raptor SpaceX methane LOX engine for the Starship Falcon 1 First rocket powered by Merlin 1A Comparison of orbital rocket engines Rocket engine Pintle injector TR 106 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 RP 1 engine used in the US Delta II launcher Saturn 1B H 1 heritage Rocketdyne F 1 LOX RP 1 main engine of the Saturn V moon rocketReferences Edit a b c d Falcon User s Guide PDF SpaceX April 2020 Archived PDF from the original on December 2 2020 Retrieved August 1 2020 a b c SpaceX Unveils Plans To Be World s Top Rocket Maker AviationWeek August 11 2011 Archived from the original on June 21 2015 Retrieved June 28 2014 a b Merlin section of Falcon 9 page SpaceX Archived from the original on July 15 2013 Retrieved October 16 2012 a href Template Cite web html title Template Cite web cite web a CS1 maint unfit URL link Mueller Thomas June 8 2015 Is SpaceX s Merlin 1D s thrust to weight ratio of 150 believable Retrieved July 9 2015 The Merlin 1D weighs 1030 pounds including the hydraulic steering TVC actuators It makes 162 500 pounds of thrust in vacuum that is nearly 158 thrust weight The new full thrust variant weighs the same and makes about 185 500 lbs force in vacuum Berger Brian July 19 2006 Falcon 1 Failure Traced to a Busted Nut Space com Archived from the original on June 4 2010 Retrieved August 2 2008 Findings of the Falcon return to flight board SpaceX com July 25 2006 Archived from the original on March 3 2013 Demo Flight 2 Flight Review Update PDF SpaceX June 15 2007 Archived from the original PDF on March 6 2012 a b Whitesides Loretta Hidalgo November 12 2007 SpaceX Completes Development of Rocket Engine for Falcon 1 and 9 Wired Science Archived from the original on March 23 2008 Retrieved February 28 2008 a b Gaskill Braddock August 5 2006 SpaceX has magical goals for Falcon 9 Nasa Spaceflight Archived from the original on March 4 2016 Retrieved February 28 2008 a b Merlin LOX RP 1 Turbopump Barber Nichols Archived from the original on May 29 2018 Retrieved May 28 2018 a b Elon Musk Feb 2005 through May 2005 Update SpaceX Archived from the original on April 15 2008 a b c SpaceX Completes Development of Merlin Regeneratively Cooled Rocket Engine Business Wire November 13 2007 Archived from the original on January 3 2008 Retrieved November 12 2007 a b c d Dinardi Aaron Capozzoli Peter Shotwell Gwynne 2008 Low cost Launch Opportunities Provided by the Falcon Family of Launch Vehicles PDF Fourth Asian Space Conference Taipei Archived from the original PDF on March 15 2012 The SpaceX Falcon 1 Launch Vehicle Flight 3 Results Future Developments and Falcon 9 Evolution PDF Archived PDF from the original on March 4 2016 Retrieved December 29 2012 a b Clark Stephen September 28 2008 Sweet Success at Last for Falcon 1 Rocket Spaceflight Now Archived from the original on September 24 2015 Retrieved April 6 2011 the first privately developed liquid fueled rocket to successfully reach orbit Boyle Alan June 4 2010 Shuttle successor succeeds in first test flight NBC News Archived from the original on December 21 2019 Retrieved June 5 2010 SpaceX Completes Qualification Testing of Merlin Regeneratively Cooled Engine Press release SpaceX February 25 2008 Archived from the original on August 22 2016 Retrieved May 31 2016 Updates December 2007 Updates Archive SpaceX December 2007 Archived from the original on April 5 2013 Retrieved December 27 2012 2007 Merlin has a thrust at sea level of 95 000 lbs a vacuum thrust of over 108 000 pounds vacuum specific impulse of 304 seconds and sea level thrust to weight ratio of 92 In generating this thrust Merlin consumes 350 lbs second of propellant and the chamber and nozzle cooled by 100 lbs sec of kerosene are capable of absorbing 10 MW of heat energy A planned turbo pump upgrade in 2009 will improve the thrust by over 20 and the thrust to weight ratio by approximately 25 Bergin Chris Davis Matt August 2 2008 SpaceX Falcon I fails during first stage flight NASAspaceflight Archived from the original on March 3 2016 Retrieved February 26 2010 Clark Stephen September 28 2008 Sweet success at last for Falcon 1 rocket Spaceflight Now Archived from the original on March 3 2016 Retrieved September 28 2008 Nelson Katherine October 8 2012 SpaceX CRS 1 Mission Update SpaceX Archived from the original on April 12 2017 Retrieved May 31 2016 Clark Stephen October 11 2012 Orbcomm craft falls to Earth company claims total loss Spaceflight Now Archived from the original on March 15 2016 Retrieved October 11 2012 Falcon 1 Users Guide Rev 7 PDF SpaceX August 26 2008 p 8 Archived from the original PDF on October 2 2012 a b Klotz Irene December 13 2010 SpaceX Sees ISS Meet up in 2011 Aviation Week Retrieved February 8 2011 The second stage went up to 11 000 km and that s with the shortie skirt SpaceX Falcon 9 upper stage engine successfully completes full mission duration firing Press release SpaceX March 10 2009 Archived from the original on December 13 2014 Retrieved March 12 2009 Full Duration Orbit Insertion Firing SpaceX January 2 2010 SpaceX Falcon 9 Upper Stage Engine Successfully Completes Full Mission Duration Firing SpaceX March 10 2009 Archived from the original on December 13 2014 Retrieved May 31 2016 SpaceX to begin testing on Reusable Falcon 9 technology this year NASASpaceFlight com January 11 2012 Archived from the original on January 9 2020 Retrieved January 11 2020 Mage Buff May 6 2016 lukealization Max is just 3X Merlin thrust and min is 40 of 1 Merlin Two outer engines shut off before the center does elonmusk Archived from the original on February 5 2017 Retrieved January 11 2020 Servo Motors Survive Space X Launch Conditions MICROMO Faulhabler 2015 Archived from the original on February 20 2017 Retrieved August 14 2015 the fuel trim valve adjusts the mixture in real time The fuel trim device consists of a servo motor controlled butterfly valve To achieve the proper speed and torque the design incorporates a planetary gearbox for a roughly 151 1 reduction ratio gearing internal to the unit The shaft of the motor interfaces with the valve directly to make fine adjustments The basic mixture ratio is given by the sizing of the tubes and a small amount of the flow of each one gets trimmed out explains Frefel We only adjust a fraction of the whole fuel flow Elon Musk November 24 2013 SES 8 Prelaunch Teleconference Archived from the original on December 3 2013 Retrieved November 28 2013 Also at SoundCloud Archived December 7 2013 at the Wayback Machine Berger Eric SciGuySpace May 10 2018 Musk Merlin rocket engine thrust increased by 8 percent to 190 000 lbf Tweet via Twitter Clark Stephen Falcon 9 rocket overcomes engine failure to deploy Starlink satellites Spaceflight Now Archived from the original on October 26 2020 Retrieved November 1 2020 Clark Stephen SpaceX s Starlink network surpasses 400 satellite mark after successful launch Spaceflight Now Archived from the original on April 30 2020 Retrieved November 1 2020 Safety panel concludes May launch of commercial crew test flight is feasible SpaceNews April 23 2020 Retrieved November 1 2020 Berger Eric October 28 2020 How a tiny bit of lacquer grounded new Falcon 9 rockets for a month Ars Technica Retrieved October 24 2021 Cao Sissi February 16 2021 SpaceX Fails Falcon 9 Rocket Landing in Rare Miss During Latest Starlink Mission Observer Retrieved February 26 2021 SpaceX SpaceX Archived from the original on March 7 2011 Retrieved September 24 2020 a b Falcon 9 SpaceX 2017 Archived from the original on February 8 2018 SpaceX Falcon 9 Data Sheet Space Launch Report Archived from the original on December 4 2019 Retrieved September 21 2019 a b Falcon 9 Launch Vehicle Payload User s Guide PDF Revision 2 SpaceX October 21 2015 Archived from the original PDF on March 14 2017 Retrieved November 29 2015 Svitak Amy November 18 2012 Dragon s Radiation Tolerant Design Aviation Week Archived from the original on December 3 2013 Retrieved November 6 2013 We ve got computers in the Falcon 9 we ve got three computers in one unit on each engine in the Falcon 9 so that s 30 computers right there Merlin LOX RP 1 Turbopump website Products page Rocket Engine Turbopumps Barber Nichols Archived from the original on March 13 2016 Retrieved November 22 2012 Musk Elon October 13 2018 Full Q amp A Tesla and SpaceX CEO Elon Musk on Recode Decode offset 01 02 08 Interview Interviewed by Kara Swisher Archived from the original on November 2 2018 Retrieved November 2 2018 the turbopump on the Merlin engine runs at 36 000 rpm it s 10 000 hp Sutton History of Liquid Propellant Rocket Engines AIAA 2006 Production at SpaceX SpaceX September 24 2013 Archived from the original on April 3 2016 Retrieved September 30 2013 SpaceX Completes 100th Merlin 1D Engine SpaceX October 22 2014 Archived from the original on April 4 2016 Retrieved October 16 2014 SpaceX Prepared Testimony by Jeffrey Thornburg SpaceRef com June 26 2015 the Merlin engine has now successfully flown to space more than 180 times with 130 on the Merlin 1D reliably delivering multiple payloads for U S Government and commercial customers to complex orbits Due to the engine s highly manufacturable design SpaceX is now producing 4 Merlin 1D engines per week with current production capacity to produce 5 engines per week far more than any other private rocket engine producer in the world Foust Jeff February 4 2016 SpaceX seeks to accelerate Falcon 9 production and launch rates this year SpaceNews Archived from the original on February 9 2016 Retrieved February 6 2016 Sources Edit Belfiore Michael January 18 2005 Race for Next Space Prize Ignites Wired External links Edit Wikimedia Commons has media related to Merlin rocket engine SpaceX official website Retrieved from https en wikipedia org w index php title SpaceX Merlin amp oldid 1111991545 Merlin 1D, wikipedia, wiki, book, books, library,

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