18 thoughts on “We Don’t Need No Stinkin’ SLS”

  1. It wouldn’t look good for NASA or Congress if two separate companies built super heavy lift rockets before SLS gets off the ground and by spending less combined.

      1. Blue Origin is a long way from getting the technology on that rocket. It’s basically vaporware. Cost is likewise unknown and nearly impossible to estimate.
        As for Bezos claim that he’s taking longer because he’s doing necessary steps which will because him to be ahead in the end it’s plain BS. How did working with H2O2 monoprops help him design his current or future rockets to begin with? The second and third stages in the BFR also look like expendables unlike any of his prior vehicles. The shrouds in the upper stage look like a copy paste from Delta IV. If anything it looks like convergent design with SpaceX. Which isn’t a bad thing, it’s better than continuing to persist in things which don’t scale. I think Bezos just doesn’t grok rockets like Musk does. It’s a good thing he seems to be delegating more and they did manage to do a LOX/LH2 engine but there are some pretty big jumps get the BFR. I still wonder for how long Bezos will continue dumping money into this hobby (it sure doesn’t make him any profit so far) without ending like Carmack did only in a bigger scale.

        1. Your comments are very sobering and on point.

          That being said, I hope things turn out rosy-er for Bezos’s efforts.

          You didn’t address Bezos’s suborbital tourism play. I’d like to see someone actually in that market.

        2. Bezos biggest handicap is he’s rich, but that means he can make mistakes and stay in the game. Vaporware is a bit harsh. What they’ve done has taught them some and the engine is in development.

          I do wish I had his handicap. The good news is it keeps SpaceX on their toes. The better news is it’s another nail in the SLS coffin. Trump may still have a hard time cancelling it because… jobs.

  2. The use of six landing legs instead of four would seem to be a huge leap beyond what SpaceX is doing.

    One thing I don’t think anyone has thought of is putting casters on the legs so they can roll the rocket around after it lands.

    1. With six legs you could potentially lift them one at a time and put (the mother of all) casters under them; no need to bring that with you.

  3. Hm. It actually seems a lot bigger than I would have expected by comparison if you break down the thrust numbers; is that just because H2 tanks are a lot bigger than kerosene?

    1. Correct. Methane is lower density than Kerosene leading to a bigger rocket. This was in fact one of the reasons why proposals to replace the side booster solids in Ariane 5 with LOX/Methane boosters never went far. SpaceX and Blue Origin will have to solve a lot of unsolved problems to get a commercially viable LOX/Methane rocket and the engine is less than half of it. The tanks are actually the major problem.

      The best proposals I have heard basically chill the Methane to a similar temperature to LOX and use a common bulkhead. The problem is if you do that then you have to keep the Methane in a narrow temperature interval. Since Methane is lower density than Kerosene the fuel tanks for Methane will always be larger and heavier using the same materials, besides that because Methane is mildly cryogenic that also adds extra tank weight because you need more insulation.

      The advantage of Methane is the extra Isp and that’s it’s allegedly easier to make a reusable staged-combustion engine around it.
      BUT another issue with Methane AFAIK is lack of proper specs like RP-1 for Kerosene. People usually think they can just use Natural Gas but Natural Gas in the market is not just plain CH4. It usually comes with heavier molecules mixed in which will cause polymerization similarly to what will happen with RP-1 and worse, because there are no decent specs for it, the level of polymerization varies according to the fuel lot. Remember the issues Goddard had with exploding Gasoline engines way back when because the composition of Gasoline sold in the market was all over the map? Similar issue.

      LOX/Methane is still a good idea IMHO but the problems to solve should not be underestimated. I hope it does not end like the H2O2/Kerosene trend in the last decade or two.

      1. The freezing point of methane can be reduced by adding other light hydrocarbons. There’s a ternary eutectic with a freezing point below the normal BP of LN2.

      2. Oh and the issues people have had with methane us not polymerization but rather corrosion due to traces of sulfur compounds. Last I heard Musk will have them purify the propellant and also gold plate the cooling channels (bare copper being rapidly corroded by 1 ppm sulfur.)

        1. Here’s an archived sci.space.tech thread where coking of light hydrocarbon fuels is discussed (with references from Henry Spencer).

          http://yarchive.net/space/rocket/fuels/propane.html

          Adding 5% ethylene to methane to promote polymerization didn’t do anything, but even traces of sulfur are a problem. This work was done back in the early 1990s.

          I expect one could clean out traces of sulfur compounds by passing the methane through hot copper powder before liquefying it. You wouldn’t need much copper to remove 1 ppm sulfur from tons of propellant.

  6. I worried that SpaceX would get so far in the lead that they’d get complacent but Blue Origin with Amazon cash to keep them going should provide what’s needed until others join the game (about 20 years from now?)

    Those touting how much ‘safer’ their higher priced options are, are setting themselves up to fall even further behind.

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