: 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.
: One center Merlin engine is fired during the final landing burn to enable first-stage vertical landings. Merlin 1Г—1
: 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 : An upgraded variant of the 1A with
: Uses a triple-redundant flight computer system on each engine to ensure high reliability during launch. 000 lbf) ~981 kN (220