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Reusable Rockets

25 Comments

CNES is getting in on the action:

Eymard was asked whether CNES is not in the position of having spent two years to catch up to SpaceX with a lower-cost expendable rocket in Ariane 6, only to find that SpaceX has moved to a partially reusable model that cuts costs even further.

“We don’t want to be in the position of appearing to follow in their footsteps all the time,” Eymard said. “But we admire what they are doing and we think it helps put pressure on all of us to do better.”

SpaceX, Blue, ULA, now the Europeans. But NASA insists on building a giant throw-away vehicle.

25 thoughts on “Reusable Rockets”

  1. CNES had a lot of studies for reusable first stages and reusable TSTOs but it never went much past paper. The DLR did do some drop tests of reusable winged first stages but that was mostly a software challenge since the hard problems of propulsion and reentry were not tackled at all.

    ESA has some flights of reentry test vehicles planned but propulsion is the real problem here.

    Like I said here before I think Ariane 6 is a step backwards and Arianespace will figure it out soon enough. Solid propulsion is not the way forward for commercial space launch. The reusability of those rockets will be nil and there will be no way whatsoever to adapt them to be reusable ever. It has some parallels with work on SLBMs but that is it. At a time of economic problems they thought they could keep their market position with low investment. Wrong.

    If ESA wants to keep their market share in the future IMO they need to fund Ariane 5 ME with the Vinci expander cycle second stage and start working on a new liquid propulsion engine that can power a first stage. It could be a large expander cycle LOX/LH2 engine like the Japanese are doing or a staged combustion LOX/Methane like the one SpaceX is working on. The solids are not going to be economically competitive and the launch environment is a lot worse in terms of vibrations etc compared to liquid propulsion.

    You will probably notice this guy was a lot less confrontational than usual. That is because he’s from CNES not Arianespace or EADS. They do make a good point though:

    CNES officials have said that in addition to the need for a high launch rhythm, a rocket with a reusable first stage would need to overcome the fact that reusability means reducing the economies of scale realized from producing lots of rocket stages and motors.

    However SpaceX is already working on how to solve this problem as well with techniques like additive manufacturing of rocket engine parts which require much less expenditure in materials and tooling. I think they still are not seeing the whole picture here.

    Elon has got a pretty good plan here. Lets hope SpaceX executes well.

  2. NASA did have the Space Launch Initiative TSTO proposal. Remember the RS-83 and RS-84 engines? It was canned shortly before Bush came to power I think.

    Had Al Gore been elected maybe it wouldn’t have been replaced with Constellation.

  3. J. R. Thompson said that “X-33 proved that reusability doesn’t work.”

    The stupid!!!! It burns…

    1. Oh, there’s much more stupid around than that. The web is full of posts saying ‘the shuttle proved reusability doesn’t work,’ and ‘SpaceX is doing nothing new with reusing their first stage, the shuttle reused its SRBs.’

  5. Shuttle, where we learned partial reusability of the second stage doesn’t lead to reductions in cost (especially not if NASA is running it).

    Falcon, where we’re yet to learn that partial reusability of the first stage doesn’t lead to reductions in cost (but, ya know, not being run by NASA certainly helps).

    Skylon, where we’re just laughing and laughing but some people aren’t laughing along because they haven’t learnt anything.

    1. Skylon is certainly moving along at a measured pace. It has been almost three years since the last subscale test of the precooler. When is the full engine demonstrator going to be built?

  6. Trent:

    I know you can do the math (and make appropriate estimations).

    Do you really think that SpaceX’s cost for refurbishment will be > the cost to produce a new first stage? Granted, no one knows the answer at this point.

    1. I kind of wonder. You know what happened with the SSME. They only tried to reduce the costs and increase reusability near the end of the life cycle. Plus the changes they made to make the Shuttle capable of reaching the ISS like using Al-Li on the ET actually ended up increasing costs even further.

      I remember reading a Shuttle cost analysis once and a large proportion of the costs was the RCS/OMS because they needed to handle toxic hypergolic fuel and that was really expensive. Near the end of the Shuttle life cycle the cost of reusing the SSME and TPS was actually lowered by a large amount due to the improved engine design in Block II and later plus the use of felt blankets for TPS which ended up reducing the amount of individual tiles which needed to be inspected. I think the lesson here is to use few parts on the TPS system if you want to reduce the reuse cost. You are probably better off manufacturing large panels and throwing them away than using that small tile puzzle. As for the engine you have to increase robustness at the cost of some performance and you want to keep the total number of parts down. But you would want this even on an expendable.

      I think it should be possible to reuse the engines relatively easily because gas-generator cycle engines are a lot simpler than staged-combustion. To reuse the entire stage with small turn around time would require a lot of integrated diagnostics and built in tolerances in the whole system. I think it helps that SpaceX already has the facilities to do a lot of engine and rocket testing. It is certainly not impossible.

      The big question is how well would the actual stage hold in an actual landing. Somehow I doubt its that impact resistant.

      1. The big question is how well would the actual stage hold in an actual landing. Somehow I doubt its that impact resistant.

        They have been doing landings in Texas.

      1. By recovering a few stages and examining wear they get a better idea of how close their structural margins actually are, allowing them to engineer for better reliability or performance.

  7. There is that Big Dumb Booster dude who pointed to the Thor-Agena, where that big, fat Thor was actually much cheaper than that bitty Agena on top. Does reusing the first stage, only, get you anywhere?

    Put another way, there were supposed to be two components to the Space Transportation System. One was the Shuttle, the other was the Space Tug, which never got built.

    Whereas low-Earth orbit is halfway to anywhere, this means it is only halfway — the interesting destinations, starting with geosynchronous orbit and going outward to various Lagrange points are farther out. How about starting with reusing the transfer stage, perhaps using aerobraking on the way back, that is refueled to “keep it up there”?

    The thing with the Agena was its on-orbit engine restart, no mean trick to get that glob of fuel in microgravity into the engine to get it going,. This and the 3-axis stabilization — in the late 1950’s — was the enabling tech of the Corona-Discoverer (and with recovery of payloads from space) was far ahead of the Space Program that was talked about. Oh nooose, we are so behind the Russians, which President Eisenhower tried to answer with “Mmmmmmm,, mm, mmmmmmmm.”

    Forget about the booster part from now. How about we figure out now only how to restart on orbit but how to transfer and store fuel and reuse the transfer stage? How about we work on the successor to the Agena?

    1. Thor and Agena were completely different stages, with very different designs. Thor, if I remember correctly, was at least based on a mass-produced nuclear missile that spread development costs over hundreds of launchers.

      I’m struggling to see how a Falcon second stage with one engine and smaller tanks could cost more than (or even come close to costing as much as) a first stage with nine similar engines and larger tanks.

    2. the interesting destinations, starting with geosynchronous orbit and going outward to various Lagrange points are farther out.

      Are you speaking from personal experience? Because every astronaut I know says otherwise.

      I don’t understand where this whole “LEO is a dump”/”stuck in Low Earth Orbit” notion comes from.

      I’m not really sure what makes geosynchronous orbit a more interesting destination, unless you like the idea of sunning yourself in the Van Allen Belts.

    4. In the old days the second stage was a lot more expensive than the first stage for several reasons. They usually used more expensive and harder to handle fuel. They used low production rate special engines. They used more mass optimized design with more expensive materials. Last but not least they had all the expensive guidance computers since the second stage is the only part of the rocket that lasts throughout the entire flight.

      Now compare that to a Falcon 9 second stage. It has the same engine as a first stage engine only the engine bell nozzle is different. The guidance computer hardware AFAIK use the same design as the first stage guidance computers. Computer hardware today is inexpensive. They do use more expensive materials in that second stage engine bell nozzle but that is about it.

      I doubt it costs as much as a first stage with nine of those engines. I would not be surprised if most of the production cost is in the engines. Why do you think SpaceX made the effort of producing the Merlin 1D? Making the engine simpler to build with less parts drove down the cost of producing the rocket. Because most of the cost today is in man-hours to produce anything. Especially in a place like California.

  8. Trent, given the money and effort he’s putting in to re-using the first stage I have a small, nagging suspicion that Elon disagrees with you. I wouldn’t be the least bit surprised to find that the engines and stage avionics architecture had re-use ability in mind quite a while ago.
    Sure the stage is likely somewhat fragile but the landing will be automated so I think it likely that it will work perfectly or not at all. Come to think of it, how fragile is a rocket stage for axial loads when it carries a second stage, payload and full fuel for takeoff, until staging? What is the mass fraction of a nearly empty first stage? In any case, why should re- use have a bad effect on reliability? Most first flights of even production airplanes have a squawk list. When these are all fixed the aircraft usually gets more reliable until old age sets in.

      1. Last I looked, the vast majority of their upcoming payload manifest had nothing to do with NASA. It’s not as though NASA will be buying enough launches to justify the effort of building a reusable Falcon, or a Falcon Heavy.

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