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.
Test firing of the Merlin 1D at SpaceX’s McGregor test stand | |
| Country of origin | United States |
|---|---|
| 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) |
| Thrust, sea-level | 845 kN (190,000 lbf) |
| Throttle range | Sea level: 845 to 482 kN (190,000 to 108,300 lbf) (57%) Vacuum: 981 to 626 kN (220,500 to 140,679 lbf) (64%) |
| Thrust-to-weight ratio | 184 |
| Chamber pressure | 9.7 MPa (1,410 psi) |
| Specific impulse, vacuum | 311 s (3.05 km/s) |
| Specific impulse, sea-level | 282 s (2.77 km/s) |
| Dimensions | |
| Diameter | Sea level: 0.92 m (3.0 ft) Vacuum: 3.3 m (11 ft) |
| Dry weight | 470 kg (1,030 lb) |
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.