: The current active version, introduced in 2013. It is designed for rapid reusability and vertical landings. Core Specifications (Merlin 1D) Sea Level (SL) Vacuum (Vac) Thrust ~845 kN (190,000 lbf) ~981 kN (220,500 lbf) Specific Impulse (Isp) Chamber Pressure 9.7 MPa (1,410 psi) 9.7 MPa (1,410 psi) Thrust-to-Weight Ratio Sources: Design Innovations

: One center Merlin engine is fired during the final landing burn to enable first-stage vertical landings.

: The first to feature a regeneratively cooled nozzle and combustion chamber. It powered the first privately developed rocket to reach orbit (Falcon 1 Flight 4) and early Falcon 9 flights.

: Drives both the LOX and RP-1 impellers. It also provides high-pressure fuel for hydraulic actuators , eliminating separate hydraulic systems.

: The initial version used an expendable ablatively cooled carbon-fiber nozzle. It flew only twice on the Falcon 1 (2006–2007).

: An upgraded variant of the 1A with a more powerful turbine; it was never used on a flight vehicle before SpaceX shifted to regenerative cooling.

: Uses a triple-redundant flight computer system on each engine to ensure high reliability during launch.