That, and it's a lot easier to shut off 90% of your engines and land at 50% thrust than it is to design an engine that will run at 5% thrust.
Oh, and if your engine is small enough, you can also use the same design on your upper stages - otherwise you need to design two engines.
Also, it may be worth pointing out that the current planned thrust for the Raptor is ~1,700kN at sea level, while the BE-4 is ~2,450 kN. They aren't actually that different - it's just BFR is massive.
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That, and it's a lot easier to shut off 90% of your engines and land at 50% thrust than it is to design an engine that will run at 5% thrust.
Oh, and if your engine is small enough, you can also use the same design on your upper stages - otherwise you need to design two engines.
Also, it may be worth pointing out that the current planned thrust for the Raptor is ~1,700kN at sea level, while the BE-4 is ~2,450 kN. They aren't actually that different - it's just BFR is massive.