3 thoughts on “SN9 Update”

  1. I posted some math on it in the earlier thread, with the landing failure rate on two engines being 2F – F^2, where F is the engine failure rate, and the three engine landing failure rate being 3F^2 – 2F^3.

    For the arbitrary standard of one landing failure per 200 flights, the two engine landings need an engine restart reliability of 99.75% (F=0.25%), whereas the three engine method only needs a reliability of 95.86% (F=4.14%).

    Of course, in practice, the RUD will probably be caused by switching a sensor from English to metric, or a stuck tank-valve, or a software bug.

  2. It didn’t make much sense to me to have three sea-level engines and only be able to make use of two of them. I understand the thrust issue, but I figured that the design plan was that if one failed, they’d try to light the unlit one, basically using it as a spare.

    My initial guess was that, due to being an early prototype, SN9 didn’t have the software needed to do that, so the failure of one engine doomed it.

  3. I think the idea of igniting all engines it good but they probably need to increase engine ignition reliability too. Plus make the engines throttle deeper.

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