This is an incredible bit of footage. It's so cool to see the engines looking sideways like a chameleon.

Raises a question: I suppose they fired 2/3 engines not because of a failure, but because 3 engines would produce too much thrust.

That does mean that in a high stakes situation (landing) you can't afford to lose an engine. I wonder if there's any margin there for lighting the third engine in case of engine failure.

A variation of that question is: in the event of a hard landing like the one today, will there be some means for humans to survive?

(Googling the question led me to an article about how Starship does not have a crew abort system, which seems like an unfortunate limitation. I suppose in theory maybe the landing is slow enough that if you know, say, a minute or in advance that something is wrong you could possibly just exit the vehicle out a door and parachute down. I'd guess that's easier said than done...)

I think their goal is to make the Spacecraft reliable enough that it wouldn't need the abort system. In the same way that 737s don't have one. However I think crew is a long way away for now. If they are launching 100 passengers it may be hard to do an abort system that isn't just the entire Starship itself. Maybe for smaller crew launches they will have ejection seats like Soyuz?

The timing of relight probably means there is a zero-tolerance to a flame-out like this when going from two to one engine. A heavier ship might be able to run more at minimum throttle so if one flames out there might(?) still time to throttle up one of survivors that is already lit, from three near mimimum to two near maximum or some combination. These things are moving literally tonnnes of fuel per second so even throttle-up inertia might lag too much unless they can predict failure really early.

One engine didn't have the grunt required(?) but SN8 might have been doomed due to fuel supplying both lit engines. Ho hum.

This was as much a test of the Raptor engines as it was the bellyflop and landing manoeuvre, perhaps more so. They've got data from literally hundreds of Merlin engines regarding failure modes etc. A long way to go with Raptor and many more explosions to be livestreamed!

Not at all sure, but some of the Falcon 9/Heavy failures seem to suggest that SpaceX's thinking on landing is "don't give up, fly it all the way to the ground," when there's an issue.

Especially with the fact that Starship is eventually supposed to fly humans and doesn't have a limit on relights since the Raptors are electrically ignited, I would bet that the software will/does include the ability to light up extra engines in an emergency.

The final rocket is supposed to have 5 or 9 raptors if I’m not mistaken.

The starship (what we saw yesterday) should have 3 sea level and 3 vacuum Raptors. The booster is currently scheduled to have 28 Raptors (some of which are fixed and some which can gimbal) although these numbers are subject to change depending on what kind of performance they can achieve in the end.

I think it’s more like 30

That's for the booster/Super Heavy right? This Starship is only the second stage of an even more ginormous rocket.

I think the 'looks like a render' effect is multiple factors; there's some distortion and the like due to distance and heat (you can sorta tell it's on a very long zoom?), high frame rate and high resolution. I think a lot of people aren't yet used to high frame rate video. I mean movies were 23 frames per second for a long time, and the reactions to 60fps films was... averse. The Hobbit was one of the first that tried that I believe, and it seriously messed with the suspension of disbelief.

edit: another comment mentions it may be 120 frames per second footage.

I know, right?! As they were cutting the first two engines off in sequence during ascent they were giving little pre-twitches to adjust the centre of gravity, like an acrobat holding another acrobat aloft hand-to-hand, switching from two hands to one. Amazing.