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My jaw dropped reading that the rocket could be re-used the next day. That seems like an enormous leap forward for space flight.

grinich 12y ago
Rockets are built to be pretty durable machines (obviously). The environment they operate in outside of the atmosphere is harsher in many ways. Two big issues with sea landing: transport (tug, crane, huge truck, etc.), and corrosion/contamination from saltwater. They'll still need to verify all systems and components before a second launch, but that's way easier to do when the vehicle is sitting empty on the pad next to all your people and equipment.
- HarryHirsch 12y ago
  They'll still need to verify all systems and components before a second launch That. You need to re-qualify the engine after each launch. The cost of labour far exceeds the cost of materials, you need to strip and re-build the thing, and you ask yourself just how much money you can save through re-using the first stage. I don't think it's much.
  - jessriedel 12y ago
    > I don't think it's much. SpaceX disagrees. They expect to cut the cost of launch by 1 order of magnitude https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Economic_issues https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...
  - mikeash 12y ago
    Unlike NASA's adventures with the space shuttle, SpaceX is a for-profit business with a goal of making money. They wouldn't be pursuing reusability if they didn't think it would increase their ability to make a profit.
  - cfreeman 12y ago
    The Merlin engine was designed from the beginning to be re-useable. They don't have to be "stripped and rebuilt" after each launch. They have already fired engines on the test stand for multiple mission durations with no problems.
  - oh_sigh 12y ago
    So, have you done more analysis on this than SpaceX has? You should send them this post of yours so they stop wasting all that money! I bet they never thought of what you said.
  - grinich 12y ago
    On traditional launch vehicles, yes. Shuttle was definitely this way. And I'm sure SpaceX will initially do a complete disassemble and inspection to gather more data about the wear and tear. But the Merlin engines have been designed from the start to be reusable and dependably reignitable, whether at sea level or upper atmosphere. They're pretty amazing-- essentially the pinnacle of +50 years of engine design. Tom Mueller is a huge badass. :) http://en.wikipedia.org/wiki/Merlin_(rocket_engine) http://en.wikipedia.org/wiki/Merlin_(rocket_engine) And check out that bad boy roar: http://www.youtube.com/watch?v=wkdReoxGHG8 http://www.youtube.com/watch?v=wkdReoxGHG8 I don't have a link on hand, but Elon has said multiple times that the majority cost of the Falcon-9 is the raw material. One of the reasons they've been able to drop the price significantly is by using more efficient manufacturing techniques, requiring less material and creating less waste. (e.g. stir-friction welding) It's also worth noting that Falcon-9 can still complete a mission with one (and perhaps two?) engine failures, which gives quite a more comfortable margin of error. There's a big difference between "perfect" and "near perfect" when it comes to engineering these things. ;)
  - ef4 12y ago
    > you need to strip and re-build the thing That's how politically-designed boondoggles like the shuttle work. It's not inevitable, if you actually spend the engineering effort on reliability and repeatability. If NASA operated an airline, they would probably be tearing down and rebuilding every jet engine after every flight, and a ticket would cost $100,000.
    - XorNot 12y ago
      I said this in another thread, but part of the issue is failure intolerance. Sure - for human payloads I'd want to be damn sure my process is good, like, hundreds to thousands of missions deep before I trusted it. But that's totally unnecessary for an unmanned payload! If the cost of launch drops enough, you can fully justify launching 2x the payloads if you expect maybe 1 in 10 failures due to the mode of launch. I suspect it's possible to do a damn site better then that, but for NASA its never been an option. If it's reusable, they can't let a mission fail because they'll only get punished and funded according to the failures, even if they specced everything expecting 1 mission to possibly not go off right.
      - 001sky 12y ago
        This is true for a sub-set of unmanned payloads. Space-X is great for the sub-set of things that don't require insurance, and don't therefore need to use corner-case mil-spec stuff with the corner case pricing. For others, the cost of losing a $1-2B bird on top of a $100m/cheap rocket is shitty math. Nobody is going to insure the top of it, so ultimately the "waste" is akin to a form of insurance. Everybody knows this already, so I'm not sure how sympathetic a hearing it is going to get. It will be great PR though to hopefully spurn <designs> that fit the new framework...and thus expand the market for space-x and hopefully limit the superflous use of corner-case technology for mundane/run-of the mill applications (at the tax payer's expense).
        rjurney 12y ago
        You really think SpaceX loads aren't insured? This seems impossible.
- mkempe 12y ago
  This was an experiment. The goal is to land on terra firma, not [mare incognitum].
  - mapt 12y ago
    For Falcon 9 though, the first stage contributes so much of the dV that it is not particularly feasible to land it at the launch site - by the time it separates, it's moving at several kilometers per second away from the launch site towards the horizon. That opens up the question of where the launch/landing site pair is bound to be. A ship-based landing system, such as a semisubmersible oil drilling rig (only ~$1B used!) with a landing pad built onto it, would seem to be close to optimal for the F9 specifically. The Falcon Heavy's 2 side boosters, on the other hand, will separate much earlier in the flight - they are likely to be much more practical to land at the launch site, particularly for direct geosynchronous payloads that allow a lot more vertical / near-vertical burn time in relation to horizontal.
    - grinich 12y ago
      Citation? Usually the flight plan is to increase altitude (less atmospheric drag) before increasing angular velocity to full orbit. Elon's been pretty explicit that F9 stage 1 will land back on the pad, or very close by.
      - mapt 12y ago
        See this thread for estimates on the dV of the different stages of these launch platforms for a full-capacity payload: http://forum.nasaspaceflight.com/index.php?topic=30685.0;all http://forum.nasaspaceflight.com/index.php?topic=30685.0;all It costs about 8km/s to get into low orbit from an atmosphere-less Earth. From our planet it costs about 9.4-1.0km/s because of aerodynamic and gravity losses. Those aerodynamic and gravity costs, and the Hohmann Transfer from groundlevel to orbit (trivial for LEO, more for GTO) are the only parts of the equation one can address while burning vertically to stay over the launch site. Assuming 10, If the first stage only has to contribute 2km/s, it can address aerodynamic and gravity losses (while thrusting vertically), and then leave the second stage to boost for the horizon and achieve full orbit all on its own. At 4-5km/s first stage contribution, it doesn't look like this is possible unless the payload is very undersized, leaving the second stage with enough dV to go from 'rising out of the upper atmosphere vertically' to 'circular orbit' all on its own. The mass is a free variable, a greater vertical component is practical in GTO (and I don't have the modelling skills to say how much), and the second stage may launch fully fueled for F9R contra to the existing pattern, so I can't be 100% sure whether F9R will be a practical return-to-launchsite option for lightweight GTO payloads.
smackfu 12y ago
I would think inspecting, cleaning, and assembling the stack would take days. So next-day is probably Musk hyperbole.
- SoftwareMaven 12y ago
  People constantly say this about him, yet he consistently comes through on what he says. I tend to favor trusting what he says about things like this now.

grinich 12y ago

Rockets are built to be pretty durable machines (obviously). The environment they operate in outside of the atmosphere is harsher in many ways. Two big issues with sea landing: transport (tug, crane, huge truck, etc.), and corrosion/contamination from saltwater. They'll still need to verify all systems and components before a second launch, but that's way easier to do when the vehicle is sitting empty on the pad next to all your people and equipment.

HarryHirsch 12y ago
They'll still need to verify all systems and components before a second launch That. You need to re-qualify the engine after each launch. The cost of labour far exceeds the cost of materials, you need to strip and re-build the thing, and you ask yourself just how much money you can save through re-using the first stage. I don't think it's much.
- jessriedel 12y ago
  > I don't think it's much. SpaceX disagrees. They expect to cut the cost of launch by 1 order of magnitude https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_development_program#Economic_issues https://en.wikipedia.org/wiki/SpaceX_reusable_launch_system_...
- mikeash 12y ago
  Unlike NASA's adventures with the space shuttle, SpaceX is a for-profit business with a goal of making money. They wouldn't be pursuing reusability if they didn't think it would increase their ability to make a profit.
- cfreeman 12y ago
  The Merlin engine was designed from the beginning to be re-useable. They don't have to be "stripped and rebuilt" after each launch. They have already fired engines on the test stand for multiple mission durations with no problems.
- oh_sigh 12y ago
  So, have you done more analysis on this than SpaceX has? You should send them this post of yours so they stop wasting all that money! I bet they never thought of what you said.
- grinich 12y ago
  On traditional launch vehicles, yes. Shuttle was definitely this way. And I'm sure SpaceX will initially do a complete disassemble and inspection to gather more data about the wear and tear. But the Merlin engines have been designed from the start to be reusable and dependably reignitable, whether at sea level or upper atmosphere. They're pretty amazing-- essentially the pinnacle of +50 years of engine design. Tom Mueller is a huge badass. :) http://en.wikipedia.org/wiki/Merlin_(rocket_engine) http://en.wikipedia.org/wiki/Merlin_(rocket_engine) And check out that bad boy roar: http://www.youtube.com/watch?v=wkdReoxGHG8 http://www.youtube.com/watch?v=wkdReoxGHG8 I don't have a link on hand, but Elon has said multiple times that the majority cost of the Falcon-9 is the raw material. One of the reasons they've been able to drop the price significantly is by using more efficient manufacturing techniques, requiring less material and creating less waste. (e.g. stir-friction welding) It's also worth noting that Falcon-9 can still complete a mission with one (and perhaps two?) engine failures, which gives quite a more comfortable margin of error. There's a big difference between "perfect" and "near perfect" when it comes to engineering these things. ;)
- ef4 12y ago
  > you need to strip and re-build the thing That's how politically-designed boondoggles like the shuttle work. It's not inevitable, if you actually spend the engineering effort on reliability and repeatability. If NASA operated an airline, they would probably be tearing down and rebuilding every jet engine after every flight, and a ticket would cost $100,000.
  - XorNot 12y ago
    I said this in another thread, but part of the issue is failure intolerance. Sure - for human payloads I'd want to be damn sure my process is good, like, hundreds to thousands of missions deep before I trusted it. But that's totally unnecessary for an unmanned payload! If the cost of launch drops enough, you can fully justify launching 2x the payloads if you expect maybe 1 in 10 failures due to the mode of launch. I suspect it's possible to do a damn site better then that, but for NASA its never been an option. If it's reusable, they can't let a mission fail because they'll only get punished and funded according to the failures, even if they specced everything expecting 1 mission to possibly not go off right.
    - 001sky 12y ago
      This is true for a sub-set of unmanned payloads. Space-X is great for the sub-set of things that don't require insurance, and don't therefore need to use corner-case mil-spec stuff with the corner case pricing. For others, the cost of losing a $1-2B bird on top of a $100m/cheap rocket is shitty math. Nobody is going to insure the top of it, so ultimately the "waste" is akin to a form of insurance. Everybody knows this already, so I'm not sure how sympathetic a hearing it is going to get. It will be great PR though to hopefully spurn <designs> that fit the new framework...and thus expand the market for space-x and hopefully limit the superflous use of corner-case technology for mundane/run-of the mill applications (at the tax payer's expense).
      - rjurney 12y ago
        You really think SpaceX loads aren't insured? This seems impossible.
mkempe 12y ago
This was an experiment. The goal is to land on terra firma, not [mare incognitum].
- mapt 12y ago
  For Falcon 9 though, the first stage contributes so much of the dV that it is not particularly feasible to land it at the launch site - by the time it separates, it's moving at several kilometers per second away from the launch site towards the horizon. That opens up the question of where the launch/landing site pair is bound to be. A ship-based landing system, such as a semisubmersible oil drilling rig (only ~$1B used!) with a landing pad built onto it, would seem to be close to optimal for the F9 specifically. The Falcon Heavy's 2 side boosters, on the other hand, will separate much earlier in the flight - they are likely to be much more practical to land at the launch site, particularly for direct geosynchronous payloads that allow a lot more vertical / near-vertical burn time in relation to horizontal.
  - grinich 12y ago
    Citation? Usually the flight plan is to increase altitude (less atmospheric drag) before increasing angular velocity to full orbit. Elon's been pretty explicit that F9 stage 1 will land back on the pad, or very close by.
    - mapt 12y ago
      See this thread for estimates on the dV of the different stages of these launch platforms for a full-capacity payload: http://forum.nasaspaceflight.com/index.php?topic=30685.0;all http://forum.nasaspaceflight.com/index.php?topic=30685.0;all It costs about 8km/s to get into low orbit from an atmosphere-less Earth. From our planet it costs about 9.4-1.0km/s because of aerodynamic and gravity losses. Those aerodynamic and gravity costs, and the Hohmann Transfer from groundlevel to orbit (trivial for LEO, more for GTO) are the only parts of the equation one can address while burning vertically to stay over the launch site. Assuming 10, If the first stage only has to contribute 2km/s, it can address aerodynamic and gravity losses (while thrusting vertically), and then leave the second stage to boost for the horizon and achieve full orbit all on its own. At 4-5km/s first stage contribution, it doesn't look like this is possible unless the payload is very undersized, leaving the second stage with enough dV to go from 'rising out of the upper atmosphere vertically' to 'circular orbit' all on its own. The mass is a free variable, a greater vertical component is practical in GTO (and I don't have the modelling skills to say how much), and the second stage may launch fully fueled for F9R contra to the existing pattern, so I can't be 100% sure whether F9R will be a practical return-to-launchsite option for lightweight GTO payloads.

smackfu 12y ago

I would think inspecting, cleaning, and assembling the stack would take days. So next-day is probably Musk hyperbole.

SoftwareMaven 12y ago
People constantly say this about him, yet he consistently comes through on what he says. I tend to favor trusting what he says about things like this now.