Merlin (rocket engine)

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Merlin is a rocket engine design developed by SpaceX for use on its Falcon 1 and Falcon 9 rockets. Merlin uses RP-1 and liquid oxygen as propellants in a gas-generator power cycle. The Merlin engine is designed for sea recovery and reuse.

The pintle style injector at the heart of Merlin was first used in the Apollo Program for the lunar module landing engine, one of the most critical phases of the mission.

Propellants are fed via a single shaft, dual impeller turbo-pump. The turbo-pump also provides high pressure kerosene for the hydraulic actuators, which then recycles into the low pressure inlet. This eliminates the need for a separate hydraulic power system and means that thrust vector control failure by running out of hydraulic fluid is not possible. A third use of the turbo-pump is to provide roll control by actuating the turbine exhaust nozzle.

[edit] Revisions

[edit] Merlin 1A

The initial version, the Merlin 1A, used an inexpensive, expendable ablatively cooled carbon fiber composite nozzle. The Merlin 1A flew only two times: First on 24 March 2006, when it exploded shortly after launch, and the second time successful on 21 March 2007. Both times the Merlin 1A was mounted on a Falcon 1 first stage.^[1][2]

[edit] Merlin 1B

The Merlin 1B rocket engine is an upgraded version of the Merlin engine developed by SpaceX for its Falcon 1 launch vehicles. It is capable of producing 85,000 lbf of thrust, over its predecessor's 77,000 lbf. The Merlin 1B has been enhanced over the 1A with a turbine upgrade (from 1490 kW to 1860 kW).

Initial use of the Merlin 1B was to be on the Falcon 9 heavy 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, the 1B will not be used on a flight vehicle. SpaceX has moved its Merlin development to the Merlin 1C, which is regeneratively cooled. Therefore the Merlin 1B was never in use on a launch vehicle.^[1][2]

[edit] Merlin 1C

The Merlin 1C uses a regeneratively cooled nozzle and combustion chamber, and has been completed with the mission duty firing (170 seconds) in November, 2007. ^[3][4]

As it will be configured for use on Falcon 1 vehicles, the Merlin 1C will have a sea level thrust of 78,000 lbs, a vacuum thrust of 90,000 lbs and a vacuum specific impulse of 301 seconds. In this configuration the engine will consume 300 lbs 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. ^[5]

[edit] Merlin 2

Plans for a Merlin 2 rocket engine with F-1-class performance and more than 1.5 million lb_f (6.7 MN) of thrust were announced early 2005. It was said that development should start in a few years and target numbers would be released in spring 2005.^[6] However, there was nothing ever to be heard again from the Merlin 2 plans. Instead, SpaceX announced the development of the Merlin 1C (see above), which is around half the size of the originally planned Merlin 2 but also regeneratively cooled. Merlin 2 was intended for use on SpaceX's future "BFR" (Big Falcon Rocket), which was (and still is sometimes) a code word for the Falcon 9 and Falcon 9 heavy, two rockets which are already in their late development phase and will now use the Merlin 1C instead ^[7].

[edit] Engine details

[edit] Performance

Current published ratings:^[8]

• Sea level thrust: 125,000 lbf (556 kN)
• Vacuum thrust: 138,400 lbf (616 kN)
• Chamber pressure: 6.14 MPa (890 psi)
• Sea level I_sp: 255 s (2.6 kN·s/kg)
• Vacuum I_sp: 304 s (3.0 kN·s/kg)
• Thrust-to-weight ratio (fully accounted): 96

[edit] Operations

• Fuel: RP-1 rocket grade kerosene
• Oxidizer: Liquid oxygen

[edit] See also

• Kestrel (rocket engine)

[edit] References