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SLS and Orion

Some Tweets Just Beg To Be Answered

By Keith Cowing
NASA Watch
July 16, 2018
Filed under

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

21 responses to “Some Tweets Just Beg To Be Answered”

  1. TheBrett says:
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    It’s probably cheaper to treat the engines as disposable than to recover them and reuse them.

    • wwheaton says:
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      The obvious counter-example to any claims of truth in general being the Falcon9 engines, which are probably the most expensive part of the first stage. Yet launch costs are said to have dropped sharply due to reuse.

      • ThomasLMatula says:
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        But must remember that the Falcon was not designed or built on a cost plus contract. Every dollar saved goes to the bottom line.

        • Jeff2Space says:
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          Vertical integration is also a good thing. When SpaceX finds that a supplier is too expensive (or unreliable), they pull the production of that component in house so they have full control over cost and quality.

        • Michael Spencer says:
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          Major Thom:

          I’ve been thinking about this comment and have a question: in what sense would something be “designed or built on a cost plus contract”?

          I don’t see the connection you are making between the method of fabrication, or perhaps the management of fabrication, and the method of being paid?

          (Here I am perhaps naively assuming that there are two honest actors).

          • Paul451 says:
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            In a cost-plus contract, there is no incentive to find savings by innovating. Indeed, for cost-plus-percentage contracts, savings actually reduces your profit. So there’s a big incentive to make the process as expensive as you can get the agency overseers to sign off on.

          • TheBrett says:
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            It’s not surprising that NASA uses them so frequently. Even aside from corruption, it’s still an agency that was formed back when saving time was more important than saving money in space engineering. That’s got to leave a legacy.

          • Paul451 says:
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            Not one of saving time, that’s for sure.

          • TheBrett says:
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            The Apollo Era funding dried up, but the legacy remains.

    • Jeff2Space says:
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      It’s only “cheaper” because the flight rate of SLS is going to be at most twice per year. At that flight rate, it’s “cheaper” to keep manufacturing new engines only because you need to keep that manufacturing line open and refurbishing used engines would require hiring more people to do the task (i.e. increasing the standing army size increases costs when flight rates are low).

      In other words, SLS is a horribly inefficient program because the entire system is disposable and results in a pathetic maximum flight rate.

      • spacegaucho says:
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        I think all these efforts are about keeping the capability in place. It’s not like the SSME was really very reusable. I believe the original target was 55 flights before refurbishment
        The claim at the end was 1 and a half (and they were doing crazy things like putting gold rods into LOX posts). Even 10 restarts for a 1000 total seconds may not be that much of an improvement since the SSME fired for about 600 seconds and had to go through acceptance testing

        • TheBrett says:
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          I could absolutely believe that a big part of it is keeping the solid-fueled rocket industry alive (given that they also use that capability to make ICBMs).

          • Paul451 says:
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            But is this waste cheaper than just directly throwing them a $billion for a “better missiles” R&D program?

          • TheBrett says:
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            Probably not, although this has the political advantage of hiding a subsidy for nuclear missile technology within a civilian program. Congress loves masking subsidies for defense needs through non-military stuff.

          • Paul451 says:
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            this has the political advantage of hiding a subsidy for nuclear missile technology within a civilian program. Congress loves masking subsidies for defense needs through non-military stuff.

            I don’t see why. They don’t seem to suffer any embarrassment when they force the military to buy systems the military says they don’t need, just because it’s in the Senator’s own state. Like more tanks than they need, when they already have row-after-row of excess tanks in storage lots in the desert.

            I feel like the ICBM argument is a lie (not yours, theirs), created post-hoc to justify the straight up corruption of the civilian program.

        • Jeff2Space says:
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          SSME is kind of on the bleeding edge. Since it had to go from sea level to vacuum, have a very high ISP, and fit three in the aft compartment of the orbiter, it ended up as an extremely high chamber pressure staged combustion engine. In laymen’s terms, it’s an impressive engine, but it’s also an extremely expensive engine to manufacture and matintain.

          The SpaceX Merlin is a respectable engine, but it’s not on the bleeding edge (lower ISP, lower chamber pressure, and etc.), so it’s a far less expensive engine to manufacture and maintain.

          Merlin/Falcon shows that you don’t have to have bleeding edge performance in order to have a low cost to orbit. Quite the contrary in fact. Cheaper engines result in larger tanks for more propellant, but propellant costs are less than 1% of Falcon launch costs, so it’s a good trade to make. Reducing the size of the stages is necessary for missiles, but not so much for launch vehicles. Falcon is notably very tall. Higher performance engines would reduce the height, but why?

          • Paul451 says:
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            it had to

            I suspect this is NASA’s biggest flaw. “It had to” because the design was locked down before they realised how difficult it was going to be. But instead of saying “this design can’t meet the goal (of cheap launch)”, they changed the goal to be the design.

      • Winner says:
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        Even twice per year is fantasy thinking.

  2. MartinH says:
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    But if it’s on Phantom Express it will be reusable, surely?

    • Saturn1300 says:
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      Yes. It was fired 10 days in a row. That is 10 flights. RS-22. They are building another engine for the test flights. Maybe they will run this engine until it dies in tests. Nice to know if the failure mode is an explosion destroying the vehicle. They also found if there was a shutdown, then a check that said it is ok, it could restart in seconds and save the mission. It is a hydrogen engine. Clean burning. May last 100s of flights.The only problem was drying the engine.

      NASA will use this engine and save a lot of money at 5m$ for 3000lbs. So a few Shuttle engines will be reused. Only one plane so if it crashes it might be the end of the program. I hope it works. It will be a huge reduction in launch costs for that size of launches. Ride share with SpaceX will be cheaper I guess. Boeing said they plan to sell launches if it works.

  3. Zed_WEASEL says:
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    From what I have read. The SSME (RS-25) are grafted with many parts from the RS-68 for use in the SLS, like the engine controller. Effectively making them a new kluge engine design with no flight history and non-reusable without a long re-certification process.