8 ms·

I imagine the refurbishment of a used Falcon 9 1st stage will involve a wee bit more than just a bit of spit and polish. It'll be examining the rocket engines

I imagine the refurbishment of a used Falcon 9 1st stage will involve a wee bit more than just a bit of spit and polish. It'll be examining the rocket engines for faults, replacement of degraded parts, examining the whole structure for defects, and replacement of any other parts if required - however, that will still be cheaper than completely building a 1st stage from scratch. Here's hoping the re-use will be a successful one!

ceejayoz 10y ago
Initially, I think you're right. Eventually, I think they're aiming for airliner-style reuse. Engineer any frequently-breaking parts to be better, then check every X flights once they've got the kinks worked out.
- walrus01 10y ago
  I am guessing it will be more like an engine rebuild on an engine for a 777 - tear down and xray of key parts. The turbopumps and compressors in a rocket engine are very sensitive, high precision parts.
  - Neeek 10y ago
    Isn't that the kind of detailed tear down that forced the shuttle in to being more expensive than traditional systems?
    - mikeash 10y ago
      Indeed. Hopefully SpaceX can do less, since their hardware is more robust. The Space Shuttle engines were driven at the edge of failure because they needed every last bit of performance. SpaceX's designs tend to go for robustness at the cost of efficiency, so they ought to need less work.
      - walrus01 10y ago
        Possibly of interest, the giant engines used in the Delta IV Heavy have 80% less part count than an SSME, but they were never intended to be human-rated: https://en.wikipedia.org/wiki/RS-68 https://en.wikipedia.org/wiki/RS-68 Not that it has brought launch costs down much, considering how the ULA loves their juicy government contracts for billion dollar NSA/NRO satellite launches. IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch.
        toomuchtodo 10y ago
        > IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch. Indeed! A Falcon 9 mission has lost an engine mid-flight, and the flight system adjusted the burn duration on the fly to compensate: http://motherboard.vice.com/blog/spacex-s-non-fatal-failure http://motherboard.vice.com/blog/spacex-s-non-fatal-failure
      - grinich 10y ago
        Plus for the orbiter refurb they had to check the entire heat shield, flight control systems, crew habitats, etc. etc. Easier when it's just the rocket + fuel tank.
        mikeash 10y ago
        Indeed. The heat shield in particular was extremely delicate and tended to get beaten up a lot coming back, so that was a huge amount of work to get ready for the next flight.
        XorNot 10y ago
        The entire spaceplane concept drastically complicated things. Capsule-based return systems are vastly simpler to operate, which is despite everything the Soyuz has been flying continuously this whole time.
  - ceejayoz 10y ago
    > The turbopumps and compressors in a rocket engine are very sensitive, high precision parts. SpaceX deliberately engineered lower performance, higher reliability engines. Think minivan instead of Ferrari. The SSMEs were genuine marvels of engineering, but that came at significant cost to reusability.
    - grinich 10y ago
      Also I think 2 of them can flame out and Falcon can still achieve the primary mission. Minivan with an extra tire.
      - JshWright 10y ago
        That depends very much on what the primary mission is. For LEO missions like the CRS flights, then sure. For GTO launches, they probably don't have the margin needed.
        skykooler 10y ago
        For a GTO mission the Falcon 9 can have a single engine out and still complete the primary mission.
        vanattab 10y ago
        Is this still true at max GTO payload weight?
        walrus01 10y ago
        It might depend where in the flight the engine fails, assuming we're talking about the first stage. If I had to guess, a GTO mission (placing a payload in a 36,000 km x 350 km elliptical orbit) could still be successful with an engine failure in the first stage after 65-75% of the fuel had been burned, and the vehicle was generally lighter, allowing the burn time to be adjusted longer to reach the same velocity at the point of first stage cutoff and separation to ignition of the second stage. But this guess comes from dozens of hours spent playing Kerbal Space Program....
  - dasmoth 10y ago
    The first few, probably yes. But I'm pretty convinced they're trying to avoid this. The engines have been test-fired many, many, times (30 starts is a figure that has been mentioned a few times. Remember that the first recovered stage (Orbcom) was returned to the launch pad and went through a static fire just a few weeks after landing. It seems clear to me that they've got their eye on reasonably-quick-turnaround reuse.
    - grinich 10y ago
      I bet they're less concerned with # of firings and more with fatigue/wear from atmosphere reentry. Very hard to test on ground.
      - dasmoth 10y ago
        They've now got 45 intact engines back, from a variety of re-entry regimes. We know they've done an all-up static fire. Several of the returned stages have had engines removed and I imagine some of these have been tested. If there's a major problem, they already know about it.
mikeash 10y ago
I wouldn't be surprised if the first one (and several beyond) costs more to refurbish than to build new. But once they get the procedure down and figure out what parts actually need attention, it should come way down.
- StavrosK 10y ago
  Not only that, but they can then add diagnostic components for subsequent launches onto the rocket, which you don't generally need if you're going to toss it after one launch.
- InclinedPlane 10y ago
  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.
deleted 10y ago
[deleted]
ricardo_mv 10y ago
The research on used components would also immensely help in the design of new rockets for spacex.
sandworm101 10y ago
If they have to go through all those checks, then that is a failure for several aspects of the program. The goal of reusability has been parts that don't need to be checked. The engines have been run over and over on test stands. They shouldn't have any faults after a single launch. If they do, then the test program wasn't accurate. If hardware needs to be redesigned to meet that goal, then it also needs to be re-tested and much of the program is back to day one. I'm sure they will do checks, but I am equally sure they dread finding something. I;m reminded of the story of Shuttle's tires. They were designed to last four or five flights, but famously were replaced every time. SpaceX wants to end such things. Parts are to do what they are designed to do. A part designed to last multiple flights without the need to be x-rayed every time, isn't going to be x-rayed every time.
- voiper1 10y ago
  It's not a failure. It would be sheer negligence to not have a full check for the _first time they've ever done this._
  - sandworm101 10y ago
    If they have cracks in things that are designed to go through multiple flights without cracks, and those cracks haven't appeared in testing, that's a failure. Any such finds in checks today means the necessity of checks again next time, and the hundreds of times after that. SpaceX needs to find nothing so that they can then decide at some later date to stop doing the checks. Not cracking open the fuel pumps after every flight is a necessary part of the planned cost reductions. If inspections suggest that the design needs to be checked every time, as with Shuttle, then new design is needed and the testing program hasn't met its goals.
    - yetihehe 10y ago
      > If they have cracks in things that are designed to go through multiple flights without cracks, and those cracks haven't appeared in testing, that's a failure. No, it's real world engineering. You can't simulate everything when you're doing something totally new. You need to make tests on real hardware to confirm that your model is good.
Gracana 10y ago
> however, that will still be cheaper than completely building a 1st stage from scratch. For a lot of companies this sort of thing is not at all cheaper. They're set up for production, not for disassembly, inspection and refurbishment. It'll be interesting to see how SpaceX tackles this as their launch service solidifies.
- Gravityloss 10y ago
  Indeed. With airliners, there are whole separate companies doing things like modifications.
pipio21 10y ago
As nobody has done it before I believe they are going to spend as much or probably more in refurbishing the old stage than building from scratch. As an engineer you get a lot of know how just doing something. The first time I used a CAD program professionally it took me like 10 times more effort and time than what it takes me now. Now is second nature. Nobody knows what it takes to relaunch a rocket. The exciting news is that they will discover it. In the end it will be way cheaper.
- Gravityloss 10y ago
  Space shuttle engines have flown all the way to orbit multiple times. However the technology was a bit different. Also see x-17 and dc-x which did multiple rocket powered flights, or all the way back to Me-163 Komet.
- grkvlt 10y ago
  > Nobody knows what it takes to relaunch a rocket Well, apart from Blue Origin, I guess. They've done four sub-orbital missions now, with their production hardware. I know there are differences, but it's a similar problem-space, so they are an existence proof that it's possible.
thescriptkiddie 10y ago
They have already done a full-length static fire of a recovered first stage. That means a full simulation of a flight with the engines running and the stage bolted down to a test stand. Obviously you can't simulate the dynamic and aerodynamic loading on the airframe, but the engines and tanks have shown that they can hold up and that was the biggest difficulty with the space shuttle. I think it's safe to assume at this point that recovered stages can be reflown without refurbishment beyond what is required to prepare a newly-manufactured stage for flight. I would put money on SpaceX putting dummy payloads or heavily-discounted commercial payloads on recovered stages and just reflying them over and over until something shows signs of stress or breaks in flight.

ceejayoz 10y ago

Initially, I think you're right. Eventually, I think they're aiming for airliner-style reuse. Engineer any frequently-breaking parts to be better, then check every X flights once they've got the kinks worked out.

walrus01 10y ago
I am guessing it will be more like an engine rebuild on an engine for a 777 - tear down and xray of key parts. The turbopumps and compressors in a rocket engine are very sensitive, high precision parts.
- Neeek 10y ago
  Isn't that the kind of detailed tear down that forced the shuttle in to being more expensive than traditional systems?
  - mikeash 10y ago
    Indeed. Hopefully SpaceX can do less, since their hardware is more robust. The Space Shuttle engines were driven at the edge of failure because they needed every last bit of performance. SpaceX's designs tend to go for robustness at the cost of efficiency, so they ought to need less work.
    - walrus01 10y ago
      Possibly of interest, the giant engines used in the Delta IV Heavy have 80% less part count than an SSME, but they were never intended to be human-rated: https://en.wikipedia.org/wiki/RS-68 https://en.wikipedia.org/wiki/RS-68 Not that it has brought launch costs down much, considering how the ULA loves their juicy government contracts for billion dollar NSA/NRO satellite launches. IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch.
      - toomuchtodo 10y ago
        > IIRC the Falcon 9 engine design is the opposite of an RS-68, which is the "one huge fucking engine" design philosophy, which is why a falcon9 has a cluster of many smaller engines and is tolerant of an individual engine failure during launch. Indeed! A Falcon 9 mission has lost an engine mid-flight, and the flight system adjusted the burn duration on the fly to compensate: http://motherboard.vice.com/blog/spacex-s-non-fatal-failure http://motherboard.vice.com/blog/spacex-s-non-fatal-failure
    - grinich 10y ago
      Plus for the orbiter refurb they had to check the entire heat shield, flight control systems, crew habitats, etc. etc. Easier when it's just the rocket + fuel tank.
      - mikeash 10y ago
        Indeed. The heat shield in particular was extremely delicate and tended to get beaten up a lot coming back, so that was a huge amount of work to get ready for the next flight.
        XorNot 10y ago
        The entire spaceplane concept drastically complicated things. Capsule-based return systems are vastly simpler to operate, which is despite everything the Soyuz has been flying continuously this whole time.
- ceejayoz 10y ago
  > The turbopumps and compressors in a rocket engine are very sensitive, high precision parts. SpaceX deliberately engineered lower performance, higher reliability engines. Think minivan instead of Ferrari. The SSMEs were genuine marvels of engineering, but that came at significant cost to reusability.
  - grinich 10y ago
    Also I think 2 of them can flame out and Falcon can still achieve the primary mission. Minivan with an extra tire.
    - JshWright 10y ago
      That depends very much on what the primary mission is. For LEO missions like the CRS flights, then sure. For GTO launches, they probably don't have the margin needed.
      - skykooler 10y ago
        For a GTO mission the Falcon 9 can have a single engine out and still complete the primary mission.
        vanattab 10y ago
        Is this still true at max GTO payload weight?
        walrus01 10y ago
        It might depend where in the flight the engine fails, assuming we're talking about the first stage. If I had to guess, a GTO mission (placing a payload in a 36,000 km x 350 km elliptical orbit) could still be successful with an engine failure in the first stage after 65-75% of the fuel had been burned, and the vehicle was generally lighter, allowing the burn time to be adjusted longer to reach the same velocity at the point of first stage cutoff and separation to ignition of the second stage. But this guess comes from dozens of hours spent playing Kerbal Space Program....
- dasmoth 10y ago
  The first few, probably yes. But I'm pretty convinced they're trying to avoid this. The engines have been test-fired many, many, times (30 starts is a figure that has been mentioned a few times. Remember that the first recovered stage (Orbcom) was returned to the launch pad and went through a static fire just a few weeks after landing. It seems clear to me that they've got their eye on reasonably-quick-turnaround reuse.
  - grinich 10y ago
    I bet they're less concerned with # of firings and more with fatigue/wear from atmosphere reentry. Very hard to test on ground.
    - dasmoth 10y ago
      They've now got 45 intact engines back, from a variety of re-entry regimes. We know they've done an all-up static fire. Several of the returned stages have had engines removed and I imagine some of these have been tested. If there's a major problem, they already know about it.

mikeash 10y ago

I wouldn't be surprised if the first one (and several beyond) costs more to refurbish than to build new. But once they get the procedure down and figure out what parts actually need attention, it should come way down.

StavrosK 10y ago
Not only that, but they can then add diagnostic components for subsequent launches onto the rocket, which you don't generally need if you're going to toss it after one launch.
InclinedPlane 10y ago
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.

deleted 10y ago

[deleted]

ricardo_mv 10y ago

The research on used components would also immensely help in the design of new rockets for spacex.

sandworm101 10y ago

If they have to go through all those checks, then that is a failure for several aspects of the program. The goal of reusability has been parts that don't need to be checked. The engines have been run over and over on test stands. They shouldn't have any faults after a single launch. If they do, then the test program wasn't accurate. If hardware needs to be redesigned to meet that goal, then it also needs to be re-tested and much of the program is back to day one. I'm sure they will do checks, but I am equally sure they dread finding something. I;m reminded of the story of Shuttle's tires. They were designed to last four or five flights, but famously were replaced every time. SpaceX wants to end such things. Parts are to do what they are designed to do. A part designed to last multiple flights without the need to be x-rayed every time, isn't going to be x-rayed every time.

voiper1 10y ago
It's not a failure. It would be sheer negligence to not have a full check for the _first time they've ever done this._
- sandworm101 10y ago
  If they have cracks in things that are designed to go through multiple flights without cracks, and those cracks haven't appeared in testing, that's a failure. Any such finds in checks today means the necessity of checks again next time, and the hundreds of times after that. SpaceX needs to find nothing so that they can then decide at some later date to stop doing the checks. Not cracking open the fuel pumps after every flight is a necessary part of the planned cost reductions. If inspections suggest that the design needs to be checked every time, as with Shuttle, then new design is needed and the testing program hasn't met its goals.
  - yetihehe 10y ago
    > If they have cracks in things that are designed to go through multiple flights without cracks, and those cracks haven't appeared in testing, that's a failure. No, it's real world engineering. You can't simulate everything when you're doing something totally new. You need to make tests on real hardware to confirm that your model is good.

Gracana 10y ago

> however, that will still be cheaper than completely building a 1st stage from scratch. For a lot of companies this sort of thing is not at all cheaper. They're set up for production, not for disassembly, inspection and refurbishment. It'll be interesting to see how SpaceX tackles this as their launch service solidifies.

Gravityloss 10y ago
Indeed. With airliners, there are whole separate companies doing things like modifications.

pipio21 10y ago

As nobody has done it before I believe they are going to spend as much or probably more in refurbishing the old stage than building from scratch. As an engineer you get a lot of know how just doing something. The first time I used a CAD program professionally it took me like 10 times more effort and time than what it takes me now. Now is second nature. Nobody knows what it takes to relaunch a rocket. The exciting news is that they will discover it. In the end it will be way cheaper.

Gravityloss 10y ago
Space shuttle engines have flown all the way to orbit multiple times. However the technology was a bit different. Also see x-17 and dc-x which did multiple rocket powered flights, or all the way back to Me-163 Komet.
grkvlt 10y ago
> Nobody knows what it takes to relaunch a rocket Well, apart from Blue Origin, I guess. They've done four sub-orbital missions now, with their production hardware. I know there are differences, but it's a similar problem-space, so they are an existence proof that it's possible.

thescriptkiddie 10y ago

They have already done a full-length static fire of a recovered first stage. That means a full simulation of a flight with the engines running and the stage bolted down to a test stand. Obviously you can't simulate the dynamic and aerodynamic loading on the airframe, but the engines and tanks have shown that they can hold up and that was the biggest difficulty with the space shuttle. I think it's safe to assume at this point that recovered stages can be reflown without refurbishment beyond what is required to prepare a newly-manufactured stage for flight. I would put money on SpaceX putting dummy payloads or heavily-discounted commercial payloads on recovered stages and just reflying them over and over until something shows signs of stress or breaks in flight.