... Are they the same engines though?
Don't get me wrong, it's impressive that the pressure tanks can take that many cryogenic cycles, but I am not sure I would call it the same "rocket".
Don't get me wrong, it's impressive that the pressure tanks can take that many cryogenic cycles, but I am not sure I would call it the same "rocket".
It's similar to a NASCAR race. They pretty much tear those down and rebuild after each race as well, but it's the "same" car.
But it matters how much an engine can be reused because it's a significant material and labor effort to produce them. Are the 9 engines from each flight reusable, and to what extent? Does half the motor get replaced each time or is it generally ok?
The Ship of Theseus debate doesn't have a hard answer to it. We can -like the Persian Immortal - respect the continuity of the thing. But so too we should track and follow the churn of the pieces, acknowledge the parts decayed. I for one am very curious how much of the ship and how much of the motor needs replacement, and how often.
Tesla's kept this one close to the chest. We really don't seem to have much data at all on how the rocket engines are doing after re-entry. The rocket engine itself might well be it's own Ship of Theseus, requiring considerable replacement. We just don't know, it's just not clear.
The engines are the most expensive part of any rocket by far. Clearly SpaceX has produced some incredible economies from reuse, but it's definitely not as clear cut as simply "reusing a single rocket twenty times".
The answer is we don't know. SpaceX have not published much detailed information about exactly what they do during booster refurbishment, how much is simply inspected, how much is replaced and how much is "swapped out".
The fastest turnaround for a booster is 21 days (and plenty have been less than 30). [1]
[1] https://en.wikipedia.org/wiki/List_of_Falcon_9_and_Falcon_He...
https://aviationweek.com/defense-space/space/spacex-building...
"For example, the company changed its requirement to perform a static firing every time an engine was removed.
“Now we have to drop three engines before we go do a static fire because we determined we can put the high-pressure joints together, verify that they’re leak-tight and everything works,” Gerstenmaier says. “We’ve removed like 14 static fires out of the flow that would have been required under our old criteria, and all 14 of those flights launched on the first attempt.”"
http://www.lpre.de/sntk/NK-33/tests.htm
В 1976 г. один из двигателей первой ступени НК-33 вместо 140 с, требуемых техническим заданием, проработал на стенде 14.000 с.
In 1976 one of NK-33 rocket engines instead of 140 seconds required by the specification run on the test stand for 14,000 seconds.