I was amazed at how resilient Starship was despite how many engines had failed, right up until the point they needed to yaw for stage separation and lost control. They've gotta improve the reliability of those engines (which I'm sure they will), but it's a testament to the quality of their control software how far they got despite having those malfunctioning engines.
Commodity parts are going to run the future. Soon we'll have commodity rocket engines and it's going to be plug and play with software accomodating X% failure per launch.
The Soviets only dreamed of such when they came up with the disaster that is the N1.
i.e not only do they make rocket engines they make the worlds most advanced and complicated rocket engines and they make so many of them you could consider them mass produced. (as far as rocket engines go that is)
These engines require a very delicate dance of chamber pressure, temperature, fuel/oxidiser mix, turbo pump speeds, etc to get started but it's all worth it in the end for their insane efficiency and thrust/weight.
Yes, SpaceX makes all their own engine, even inventing their own materials. They are building these very vertically integrated. SpaceX is pretty much the undisputed best rocket engine company in the world. They build more engines then anybody in the world and its not even close. And the Raptor is the most advanced engine in the world.
Rocket engines have different challenges then airplane engines. They are as hard in some ways but easier in others.
Rocket engine operate in a far more extreme environment, peak stressed are far larger, failures and issues far more violent. But the big advantage is that they only have to operate for a few minutes at the time (at least on the first stage). Jet engines need to operate for 1000s of hours.
SpaceX has upped the level significantly, interdicting higher efficiency full flow stage combustion and making them reusable and being able to launch quickly and reliably. So they complexity of Raptor is much higher then your typical first stage rocket engine.
I would say the complexity of a modern jet engine might still be higher, but its hard to estimate these things. Not sure how you would do that scientifically.
