: 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.
: 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. Merlin 1Г—1
: One center Merlin engine is fired during the final landing burn to enable first-stage vertical landings. : The first to feature a regeneratively cooled
: Based on the Apollo Lunar Module landing engine, this provides excellent stability and allows for deep throttling. Merlin 1Г—1
: The initial version used an expendable ablatively cooled carbon-fiber nozzle. It flew only twice on the Falcon 1 (2006–2007).