One of only a few full-flow staged combustion engines ever produced, and certainly the only one produced in any great numbers or that has powered a flight-vehicle.
'As with Merlin, Raptor has seen several iterations. Initial sub-orbital flight testing of Starship used Raptor 1 engines. Later improvements saw the introduction of Raptor 2, which was the engine used during Orbital Flight Test 1 (OFT-1). Development continues, with a Raptor 3 variant undergoing hotfire testing.
