3 ms·

That would actually be incredibly surprising, shocking, in fact. There's really only so much work that can be done inspecting and refurbishing the rocket stages

That would actually be incredibly surprising, shocking, in fact. There's really only so much work that can be done inspecting and refurbishing the rocket stages, they only have so many systems. They are precisely the opposite sort of beasts as the Space Shuttles which were some of the most complicated systems ever created by mankind. The Falcon 9 boosters are pretty much just engines, propellant tanks, avionics, and some miscellaneous bits. There's just not a ton to inspect and not a ton that can go wrong. More importantly, the vast majority of the cost of the vehicle is in the engines and tanks. The tanks are unlikely to degrade from launch to launch and are practically binary in their serviceability (they either work or they don't). Engines are incredibly expensive to manufacture and realistically the amount of inspection work that would need to be done to match that cost is just mind-boggling, and there's no good reason to imagine they'd need to do more than bore scoping. Especially since at this point if they find a potentially problematic engine, they just unbolt it and bolt on a brand new one. This increases costs a bit, of course, but it still saves a tremendous amount of costs. If the incremental flight cost of a first stage goes from the full manufacturing cost down to the cost of an engine or two plus recovery, inspection, and refurbishment, that's at a minimum tens of millions of dollars saved.

Retric 10y ago
They would be well served by doing destructive tests on a wide range of components even if they pass inspection. Further, while a simple design this also means they are relatively cheap to manufacture.
- InclinedPlane 10y ago
  It's possible that they've already reflown returned engines without telling anybody. There are some indications that this has happened, and it would be a fairly safe thing to do on some flights (since the Falcon 9 can deal with an engine out situation, even at T+0). It's likely they'll do just that with engines and other components in the future as well, such as landing legs and grid fins.
Shivetya 10y ago
I figure a lot of the extra time and money spent is confirm expectations on how well the individual components held up to the stress. Throw in a few flights and you might start to see more fatigue issues creeping in and the test is, are they occurring where expected or not. that temperature range they operate in has to have some strong effects too
jakub_h 10y ago
"Engines are incredibly expensive to manufacture" Well, the Shuttle engines were, on the order of $50M or something like that. But the Merlin-1D, according to a former SpaceX employee on Reddit, is in the ballpark of $1M per unit. They've really streamlined the design for mass production, so even if thrown away after a single use, the Merlins are actually much cheaper than the Shuttle engines even if you take RS-25 reuse into consideration (9 launches per one RS-25 unit in average - so about $5-6M per engine-launch in just amortized manufacturing costs?). They're also much simpler and sturdier, much like the F-1 engines - despite not being designed for it, it turned out that those could have been used for about twenty-thirty times without major problems and without major component replacements. The RS-25s pretty much required general overhaul after every flight.
- mikeash 10y ago
  Note that the SSME puts out about 3x the thrust and has a substantially better specific impulse, so you should probably be comparing one RS-25 to 3-5 Merlins. On the other hand, that SSME cost figure is probably in 1970s-era dollars....
- InclinedPlane 10y ago
  And the Falcon 9 first stage has nine engines, so that's about 9-14 million dollars worth of engines for the stage. That's in the ballpark of a quarter of the total hardware cost of the booster, and that almost certainly doesn't include the testing overhead for each engine. Anyway, my point is, even if all that SpaceX had to work with for reuse was the main rocket body and a pile of the majority of the engines in working order, that would easily add up to tens of millions of dollars worth of equipment, and thus tens of millions of dollars of cost savings on reflight. There's practically no way that reflight could be more expensive than a new rocket, there's just not enough complexity in the vehicle for that to realistically be possible.
  - jakub_h 10y ago
    True. I've long held the view that low costs of launches basically require two things: the equipment should be cheap to manufacture and cheap to service. Shuttle violated the former big time and in all likelihood also the latter. F9 certainly satisfies the former already and there's no reason to think that it won't eventually satisfy the latter, too.

Retric 10y ago

They would be well served by doing destructive tests on a wide range of components even if they pass inspection. Further, while a simple design this also means they are relatively cheap to manufacture.

InclinedPlane 10y ago
It's possible that they've already reflown returned engines without telling anybody. There are some indications that this has happened, and it would be a fairly safe thing to do on some flights (since the Falcon 9 can deal with an engine out situation, even at T+0). It's likely they'll do just that with engines and other components in the future as well, such as landing legs and grid fins.

Shivetya 10y ago

I figure a lot of the extra time and money spent is confirm expectations on how well the individual components held up to the stress. Throw in a few flights and you might start to see more fatigue issues creeping in and the test is, are they occurring where expected or not. that temperature range they operate in has to have some strong effects too

jakub_h 10y ago

"Engines are incredibly expensive to manufacture" Well, the Shuttle engines were, on the order of $50M or something like that. But the Merlin-1D, according to a former SpaceX employee on Reddit, is in the ballpark of $1M per unit. They've really streamlined the design for mass production, so even if thrown away after a single use, the Merlins are actually much cheaper than the Shuttle engines even if you take RS-25 reuse into consideration (9 launches per one RS-25 unit in average - so about $5-6M per engine-launch in just amortized manufacturing costs?). They're also much simpler and sturdier, much like the F-1 engines - despite not being designed for it, it turned out that those could have been used for about twenty-thirty times without major problems and without major component replacements. The RS-25s pretty much required general overhaul after every flight.

mikeash 10y ago
Note that the SSME puts out about 3x the thrust and has a substantially better specific impulse, so you should probably be comparing one RS-25 to 3-5 Merlins. On the other hand, that SSME cost figure is probably in 1970s-era dollars....
InclinedPlane 10y ago
And the Falcon 9 first stage has nine engines, so that's about 9-14 million dollars worth of engines for the stage. That's in the ballpark of a quarter of the total hardware cost of the booster, and that almost certainly doesn't include the testing overhead for each engine. Anyway, my point is, even if all that SpaceX had to work with for reuse was the main rocket body and a pile of the majority of the engines in working order, that would easily add up to tens of millions of dollars worth of equipment, and thus tens of millions of dollars of cost savings on reflight. There's practically no way that reflight could be more expensive than a new rocket, there's just not enough complexity in the vehicle for that to realistically be possible.
- jakub_h 10y ago
  True. I've long held the view that low costs of launches basically require two things: the equipment should be cheap to manufacture and cheap to service. Shuttle violated the former big time and in all likelihood also the latter. F9 certainly satisfies the former already and there's no reason to think that it won't eventually satisfy the latter, too.