Quote from: Lee Jay on 03/13/2017 04:19 pmSRBs = Falcon 9 first stageET = Falcon 9 second stage tankSSME's = MVACOMS system (and orbiter) = Dragon.Since people disagree, I guess I should explain my thinking.The STS SRBs are both tank and engine (like Falcon 9 stage 1) which provide most of the thrust for first-stage flight and which stage at about the same speed at which the Falcon 9 first stage separates from the second stage when Falcon is used in reusable mode.The ET and SSME's each achieve orbital velocity, just like the Falcon 9 second stage and the MVac. This is an enormously higher speed than SRB staging/Falcon stage 1 sep.The orbiter and its OMS pods do the same thing as Dragon and its RCS system - allow small delta-V changes on orbit to the cargo/person carrying system, and achieve re-entry.
SRBs = Falcon 9 first stageET = Falcon 9 second stage tankSSME's = MVACOMS system (and orbiter) = Dragon.
Quote from: vanoord on 03/14/2017 11:35 am That means there's still going to be a need to build new engines; and the fixed costs will still keep being covered.Well, but that's the point, isn't it: how many new engines will be built to "cover" these fixed costs.If flight rates don't go up dramatically the result of re-use will be that these newly built engines will become more expensive than before, so "how much does an engine cost" will no longer be the same.These metrics are more important than average figures at some current state.You can attribute these costs wherever you like but they won't go away, it's not like "oh, SpaceX now reuses engines 90% of the time so they are saving 90% of the cost". In Reality, between fixed costs, refurbishment etc. it will probably be closer to 50% or so.There's a reason SpaceX estimates the overall cost savings through reuse at about 30%.
That means there's still going to be a need to build new engines; and the fixed costs will still keep being covered.
Quote from: pippin on 03/14/2017 05:08 pmQuote from: vanoord on 03/14/2017 11:35 am That means there's still going to be a need to build new engines; and the fixed costs will still keep being covered.Well, but that's the point, isn't it: how many new engines will be built to "cover" these fixed costs.If flight rates don't go up dramatically the result of re-use will be that these newly built engines will become more expensive than before, so "how much does an engine cost" will no longer be the same.These metrics are more important than average figures at some current state.You can attribute these costs wherever you like but they won't go away, it's not like "oh, SpaceX now reuses engines 90% of the time so they are saving 90% of the cost". In Reality, between fixed costs, refurbishment etc. it will probably be closer to 50% or so.There's a reason SpaceX estimates the overall cost savings through reuse at about 30%.I suspect there is a wide hysteresis in the cost curve. On the way up, economies of higher production rates can significantly decrease unit costs. On the way back down (decreasing production rate after production process is mature), the increase in unit cost should be much less than the efficiencies on way up.Think of it this way... on way up, a manufacturer fully automates the production process (or nearly so). Robots, tooling, 3D printers, whatever are bought and manufacturing process debugged to get required quality and production rate. Once there, a cutback in production doesn't necessarily increase the unit cost at all.
I am confident the workforce can mostly switch to building Raptor without losing the ability to build Merlins.
So the cost per unit should not go up too much.
I do believe that they will switch to all methane Raptor vehicles not too far in the future, less than 10 years.
And let's not forget a Raptor powered stage needs to be pretty large to land.
Quote from: pippin on 03/14/2017 11:08 pmAnd let's not forget a Raptor powered stage needs to be pretty large to land.New Glenn sized should do nicely.
Quote from: envy887 on 03/14/2017 11:09 pmQuote from: pippin on 03/14/2017 11:08 pmAnd let's not forget a Raptor powered stage needs to be pretty large to land.New Glenn sized should do nicely.Can Raptor throttle that deep? Isn't Raptor quite a bit bigger than BE-4?
Quote from: vanoord on 03/13/2017 09:08 pmWhat's a Merlin these days? About $2m apiece? Well worth the costs of recovery and refurb.And since you seem to have insight into SpaceX's cost structure: how much of these 2mil are fixed costs (tooling, minimum staff,...) that you don't save on if you build one less?
What's a Merlin these days? About $2m apiece? Well worth the costs of recovery and refurb.
It may take SpaceX another 4-5 years to get to 10+ flights per core and a 1-2 month turn around, which will still be worth it.
Quote from: pippin on 03/14/2017 11:13 pmQuote from: envy887 on 03/14/2017 11:09 pmQuote from: pippin on 03/14/2017 11:08 pmAnd let's not forget a Raptor powered stage needs to be pretty large to land.New Glenn sized should do nicely.Can Raptor throttle that deep? Isn't Raptor quite a bit bigger than BE-4?Much deeper than Merlin. Supposedly to 20%
The question is: deeper than BE-4?
Lim said, with the new process in place, SpaceX no longer will have to send boosters to a company facility in Texas for testing."They will be staying in Florida — outside of a quick trip to outer space," Lim said.Within a few months, rocket refurbishing times will be cut to two to four weeks, down from the current six to eight weeks, Lim said.
Hard to imagine 2-4 weeks not being 'economically viable.'