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SpaceX Merlin
Rocket engine in SpaceX Falcon launch vehicles / From Wikipedia, the free encyclopedia
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.
![]() Test firing of the Merlin 1D at SpaceX’s McGregor test stand | |
Country of origin | United States |
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Manufacturer | SpaceX |
Application |
|
Associated LV | Falcon 1 · Falcon 9 · Falcon Heavy |
Status | Active |
Liquid-fuel engine | |
Propellant | LOX / RP-1 |
Cycle | Gas-generator |
Performance | |
Thrust, vacuum | 981 kN (221,000 lbf)[1] |
Thrust, sea-level | 845 kN (190,000 lbf)[1] |
Thrust-to-weight ratio | 184 |
Chamber pressure | 9.7 MPa (1,410 psi)[2] |
Specific impulse, vacuum | 311 s (3.05 km/s)[3] [needs update] |
Specific impulse, sea-level | 282 s (2.77 km/s)[3] [needs update] |
Dimensions | |
Diameter | Sea level: 0.92 m (3.0 ft) Vacuum: 3.3 m (11 ft) |
Dry mass | 470 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.