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So, this is an interesting twist. Elon Musk responding to a question:
Saw it in a discussion on NSF: https://tinyurl.com/4jgudzmy
The consensus is he was not being sarcastic. Implying that they may very well work on igniting three to start the flip then shut off one if all three are running well (otherwise shut off one that's not working well, or at all).
Certainly a lot simpler, faster, and safer than igniting the third one only if one of the first two have a problem, at not very much cost in fuel.. That presumes the plumbing can handle that much of a brief surge (150%) in fuel flow, unless they start up the three at say 2/3 throttle of the throttle level they have previously used for two for the same fuel flow as with two (if they did do 2./3 throttle before shutting the 3rd engine down, then it might not even use much extra fuel. Though it *might* be safest once vertical to get all three to full throttle before shutting one down, to be sure at least two are working at 100%. It does occur to me now that at say 2/3 throttle, the ISP (efficiency) of the the engines probably take a hit compared to 100%, so a bit of cost in fuel regardless).
Update - I saw in a Facebook group, that many are assuming Musk WAS being sarcastic and making fun of the guy who asked the perfectly valid question (and some fanbois piling on). Oh I hope Musk is not that much of an A-hole to have really meant that sarcastically. I had taken it as a self-humbling response, implying that in retrospect they should have thought more about that kind of thing. Why the h*** come out of a self-imposed Twitter "time out" to be an A-hole? I will note that the people on NSF who think he was not being sarcastic are more technically oriented and less fanboi-ish than the Facebook group. One literally said it's his company and his money....he can do as he wants.... as though THAT entitles anyone to treat anyone badly (and this is why I hate the "Elon can do no wrong" Fanboi cult mentality). Anyway, I did want to add this counterpoint that he might have been sarcastic and therefore no 3rd engine for the flip.
Update two - It occurred to me that they might not have installed plumbing from the header tanks (landing fuel) to the third engine's plumbing, since they didn't plan to ignite it for landing. In that case, even if they do go for a 3rd engine for landing, it would not be tested on SN-10, or the other prototypes that are too far along in assembly to retrofit them for that capability. It would have to be added in for later prototypes. I hope they do have the plumbing capable of doing that already though, if they wanted to try it.
Saw it in a discussion on NSF: https://tinyurl.com/4jgudzmy
The consensus is he was not being sarcastic. Implying that they may very well work on igniting three to start the flip then shut off one if all three are running well (otherwise shut off one that's not working well, or at all).
Certainly a lot simpler, faster, and safer than igniting the third one only if one of the first two have a problem, at not very much cost in fuel.. That presumes the plumbing can handle that much of a brief surge (150%) in fuel flow, unless they start up the three at say 2/3 throttle of the throttle level they have previously used for two for the same fuel flow as with two (if they did do 2./3 throttle before shutting the 3rd engine down, then it might not even use much extra fuel. Though it *might* be safest once vertical to get all three to full throttle before shutting one down, to be sure at least two are working at 100%. It does occur to me now that at say 2/3 throttle, the ISP (efficiency) of the the engines probably take a hit compared to 100%, so a bit of cost in fuel regardless).
Update - I saw in a Facebook group, that many are assuming Musk WAS being sarcastic and making fun of the guy who asked the perfectly valid question (and some fanbois piling on). Oh I hope Musk is not that much of an A-hole to have really meant that sarcastically. I had taken it as a self-humbling response, implying that in retrospect they should have thought more about that kind of thing. Why the h*** come out of a self-imposed Twitter "time out" to be an A-hole? I will note that the people on NSF who think he was not being sarcastic are more technically oriented and less fanboi-ish than the Facebook group. One literally said it's his company and his money....he can do as he wants.... as though THAT entitles anyone to treat anyone badly (and this is why I hate the "Elon can do no wrong" Fanboi cult mentality). Anyway, I did want to add this counterpoint that he might have been sarcastic and therefore no 3rd engine for the flip.
Update two - It occurred to me that they might not have installed plumbing from the header tanks (landing fuel) to the third engine's plumbing, since they didn't plan to ignite it for landing. In that case, even if they do go for a 3rd engine for landing, it would not be tested on SN-10, or the other prototypes that are too far along in assembly to retrofit them for that capability. It would have to be added in for later prototypes. I hope they do have the plumbing capable of doing that already though, if they wanted to try it.
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