Full flow staged combustion cycle, never been flown* before, explained here: https://everydayastronaut.com/raptor-engine/ https://everydayastronaut.com/raptor-

Full flow staged combustion cycle, never been flown* before, explained here: https://everydayastronaut.com/raptor-engine/ https://everydayastronaut.com/raptor-engine/ * The Russians built one in the 60s but it never got past static fire tests