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And here, as promised is the video with Elon Musk talking in some detail (not TOO much detail...) about the start sequence of Raptor2 engine, compared to Merlin engines etc :I can post a video tomorrow of Elon talking a bit about the Raptor's engine-lighting procedure. He is quite deliberately vague as it's SpaceX guarded info exactly what happens but it's very obvious it's unusual and complex and things need to work exactly right for engine ignition to happen reliably.
The reason I'm posting this is because it seems quitre apparent to me that there is still a re-light reliability problem with the Raptor 2.0 engine which makes me suspect that Raptor 2.1 (or Raptor3.0) is in development and will be used sometime this year or next year, to try to fix this issue.
Timestamped:
A short transcript excerpt from that video regarding the ignition sequence etc I am providing here :
Note for transcript below :
Merlin refers to the Merlin engine that powers the Falcon9 and FalconHeavy rockets.
Raptor refers to the much more complex engine that powers Starship system 1st stage booster and 2nd stage Starship.
Elon: "for Raptor1 we have torch igniters in the main chamber..... for Raptor2 has no torch igniters in the main chamber."
Interviewer: "How does it light then?"
Elon: " well....that's secret sauce".
Elon : "If the pre-burner doesn't light or doesn't light exactly right....you've got a challenge. The start sequence for Merlin engine much easier and simpler than the start sequence for Raptor. For Raptor you've got an Oxygen powerhead and a fuel powerhead and they're different shafts and you've got two turbines and two pre-burners and they're crossfeeding one another. So the start sequence for Raptor is insanely complicated compared to the start sequence for Merlin.
You're doing this delicate dance between the fuel power-head and the oxygen power-head and if they get out of synch then you can go stoichiometric in the pre-burners and melt or explode the pre-burners. So.....starting an engine like this is very complex."
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