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