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Comment by Banthum | Hacker News Reader

Is there info on how many times a Falcon 9 stage can be used before it's simply worn out?

The information on this literally doesn't exist yet. They're discovering it right now by trying to actually re-fly the first rocket. As they re-fly more of them, they will learn more about what wears out and how fast. Then they can build versions that don't wear out so fast and need less refurbishment using that knowledge.

Not really, I get a lot of my in depth SpaceX info and analysis from r/spacex (which is a pretty great little community, and one of the best places to track behind the scenes SpaceX stuff) and all I've picked up from there is "probably at least once".

It'll also depend on the difficulty of each orbit, rockets that reach higher and/or deliver payloads with more extreme orbital inclinations, experience more stress and are less likely to be reliable enough to be reused.

I think the current design can survive ~10 reuses? [1]

However, the next and last iteration of Falcon 9, Block 5, is supposed to survive much more reuses, and easier to refurbish.

[1]: https://www.reddit.com/r/spacex/comments/590wi9/i_am_elon_mu...

They've ground-tested boosters with full-flight equivalent burns hundreds of times without seeing any serious degradation. Of course that's not the same as putting them through re-entry and landings. Block 5 will include improved legs and I'm sure they will make other improvements based on lessons learned from examining the recovered boosters.

Personally I'd expect the main stresses on the system to be due to running the engines. I see no reason to suppose that the other stresses the cores experience in flight can't be engineered round to a similar degree of resiliency.

Not hundreds, but they have tested one of the boosters they recovered about 8-10 times through a full flight cycle in Texas. Doing it hundreds of times would cost a lot of money just in propellant! And the boosters (pre-Block 5) are supposed to be good for around 10 uses.

And they do test the engines a LOT. Each new engine is separately acceptance-fired (less than full mission, but not just a burp) in Texas, then integrated into a full stage and acceptance-fired again in Texas. Then, the stage is brought to the launch site and a very short static fire test is done. If there are any last-second aborts (i.e. after engine ignition but before clamp release), that puts another short cycle on the engine. So launch will be at least the 4th firing of each engine. And if it's the center engine, it'll do a boost-back burn, an entry burn, and a landing burn. So the engines get a lot of work done even on a nominal mission before we talk about reflying the stages.

And since each Falcon 9 takes 10 engines, that means they do (depending on the mission type) around 40-50 engine firings per launch, so yeah, over a half dozen or so launches, they ARE indeed doing hundreds of engine firings, just not all on the same engine and same booster.

Not yet, and as every stage requires refurbishment the question is more, what do you need to replace or inspect after how many flights. Gwynne Shotwell said that while this stage's refurbishment took 4 months it'll be less than that going forward with what they've learned. Further to that, the Falcon 9 block 5 is going to be a version that incorporates revisions to increase reusability.

A simple answer to your question. We don't know yet, and it's going to be changing for a while yet.

I don't think it's likely a system designed for say 30+ reuses and short go around time and high reliability is so close to the current system. It might look similar on the outside, but might have different propellant, different engine cycles and be made of different materials, maybe also have different staging.

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