The Evolution Of SpaceX Rocket Engines
Kestrel is a small pressure-fed RP-1/LOX engine, it was only used on the upper stage of the Falcon 1. 6,300 lbf thrust.
Merlin is the workhorse RP-1/LOX engine used on both stages of Falcon 9 and Falcon Heavy. It got completely redesigned multiple times, the current Merlin 1D and the original Merlin 1A are distantly related. In the same way, the original Falcon 9 1.0 and the current Falcon 9 1.2 Block 5 are very distantly related. It is the current world champion in thrust to weight, which is an important thing for booster engines. It’s suboptimal for the second stage, but SpaceX is working on Starship instead of optimizing Falcon 9. 190,000 lbf thrust.
Draco is an RCS engine, a small MMH/N2O4 engine used to manoeuvre the Dragon capsule in space. 90 lbf thrust.
SuperDraco are much bigger versions of Draco. They were supposed to be used to land Dragon capsule, but since they gave up on that they are only used for abort. We saw them used on the two abort tests Crew Dragon did (from a launch pad and during max Q on top of a Falcon 9). 16,000 lbf thrust.
Raptor is the new Methane/LOX engine, it’s for Starship. Like with Merlin, there is a variant with a vacuum nozzle. Methane should enable more reuse without refurbishment because RP-1 (kerosene) clogs cooling channels. Also, it’s the first full-flow staged combustion engine to fly in the world, the most advanced rocket engine cycle that is difficult to develop but should be more efficient and good for turbopump longevity. 510,000 lbf thrust.
