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Comment by perlgeek | Hacker News Reader

It's kinda wild that just a few years ago, NASA preferred to launch humans on brand-new rockets, rather than on ones that have flown multiple times and shown their capabilities.

It'll be interesting to see how the bathtub curve will look like for reused rockets, once we have more data on them.

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My guess is we'll find F9 boosters good for between 20 and 25 launches before refurb becomes expensive enough that it's better to weld up some new tanks and build another batch of Merlins. There will be a pretty big range I think. We already see they've got favorites that are far outpacing the rest of the fleet presumably because they're easier to refurb and refly. So, I think some will retire around 15 flights, and some around 30, with the low 20s being the top of the bell curve.

> We already see they've got favorites that are far outpacing the rest of the fleet

My guess is that they are keeping some in the low #s so they are available for external customers, and running others through the gauntlet for Starlink launches. Like all things equal they'd rather have 1 rocket with 4 launches and 1 with 20, than both with 12.

We know for sure that even later in the Block 5 generation the re-usability got better. So that isn't controversial.

I would assume their 'favorites' are being pushed in order to get engineering information on those flights, not because they are superior to the others of the same build.

Are individual rockets and subs considered safer after each trip? I thought it was the opposite since they endure so much stress, and one has to do expensive inspections and scans to ensure they're still flight/dive worthy.

I think that's why there is a bathtub curve. New rockets are more risky because they could have manufacturing flaws and old ones may be worn to the point they fail. The middle is the safest because they have been thoroughly tested but not worn. We seek to find how many times is the limit.

> New rockets are more risky

It’s important to note that this is technically not true.

It is an assumption that is true for other stuff and -maybe- could be true for rockets but 1) the last hundred Falcon 9 launches worked flawlessly regardless if the booster was new or not and 2) every other rocket company launches only new rockets.

Would you rather fly on an airplain's maiden flight or its second flight. For me, the wear is far less a concern than a quality control failure at manufacture. I want flight proven but I also don't want the flight leader in the fleet. There's a sweet spot between, "they're still working out bugs from the factory" and "the core, non-replaceable systems are starting to wear out." My guess is that's around 20 or so flights for an F9 booster, maybe a bit more.

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