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Falcon Heavy Merlin Engines
The Merlin engine that powers the first stage of Falcon 9 was developed by SpaceX, but draws upon a long heritage of space-proven engines. A key design at the heart of Merlin, the pintle injector, was first used for the Apollo lunar landing module. The nine-engine architecture is also an improved version of the design employed by the Saturn I and Saturn V rockets of the Apollo program, which had flawless flight records in spite of engine losses.
Burning liquid oxygen and rocket-grade kerosene propellant, a single Merlin 1D engine emits 654 kilonewtons (147,000 pounds) of thrust at liftoff, rising to 716 kilonewtons (161,000 pounds) as it climbs out of Earth’s atmosphere. The engine’s vacuum specific impulse—an efficiency figure that represents the amount of thrust generated relative to the amount of propellant used—is an exceptionally high 309 seconds. Merlin’s thrust-to-weight ratio exceeds 150, making the Merlin 1D the most efficient booster engine ever built, while still maintaining the structural and thermal safety margins needed to carry astronauts. Merlin is manufactured in-house by SpaceX.