19 thoughts on “SLS And Moon In 2024”

  1. I see where he can get the Orion to LLO, but I don’t see how a lander gets to LLO. Is the hypothetical lander being sent separately?

    1. @ George Turner,

      If I read it right, any lander would have to be sent separately, because the mass budget is somewhat tight as is with just Orion.

      However, while I applaud Denis Wingo for laying out a plausible way to get Orion into LLO (and showing that Gateway is indeed useless), the huge problem IMHO is that with or without EUS, SLS/Orion is not useful for moon (or for that matter, space) missions, due to cost.

      Dragon 2 should be quite capable (and lighter than Orion) for a moon mission in place of Orion. What it, like Orion, lacks is a suitable service module, though Dragon2 is worse off in this regard (a delta/v potential of about 300ms compared to Orion’s 1800). I tried crunching some numbers to see if installing a Star-38 solid rocket in the trunk (I know that would be a formidable design task, but I think it’s feasible) could do the job. Looks like with it Dragon can get into LLO, or out of it (Dragon 2 has about 300MS delta/v capacity as-is), but alas, not both. But… I wonder if there’s a LOX/Kerosine version of his IVF, and if it could work on a FH 2nd stage in order to allow the 2nd stage to place Dragon into LLO, and on a separate mission place a lander into LLO?

      Probably the biggest (though not only) flaw in my above paragraph is that the lander, in order to be placed into LLO for use, must exist, and it does not.

      1. There is no “Star 38”, but there is a Star 48. Unfortunately, the lead time to qualify the titanium forgings is 24 months, followed by lengthy process of building and firing a qual motor. Add on the contract negotiations, and you’re way, way past 2024.

        1. Thanks, MfK,

          My bad on the number, was going from memory, always a bad idea. 🙂

          Seriously, a lead time of 24 months? And for what titanium forgings? SpaceX can print Inconel for rocket thrust chambers, surely they could print tie rods if they couldn’;t just order them?
          Ah, I’m forgetting the qual times for anything manned, aren’t I? (and Star48 isn’t man-rated). But, wouldn’t such qual times be even worse for hardware that is all new with no flight history?

          1. If the Dragon 2 dry weight is 9,525 kg and it’s loaded with the maximum of 6,000 kg of cargo, including the dry weight of the service module and Star 48B (propellant mass of 2,011 kg and an ISP guess of 295 sec), the delta V from the Star should come to 352 m/sec. If you only loaded the Dragon with 1125 kg, including the SM weight, you could get 500 m/sec. That’s still well short of what’s needed.

      2. Building a good service module shouldn’t be that difficult. The RS-72 (Aestus II) engine, with 6,650 lbf thrust, uses the normal N2O4/MMH hypergolic mix running at 160 psi with an 84:1 expansion ratio, for an ISP of 324 seconds. That is better than the 100-120 psi engines used on Apollo’s SM, or the Space Shuttle OMS, which gave something around 310 seconds ISP.

        Or they could put a proper vacuum bell on a Draco or Super Draco (or something in between). With a chamber pressure of 1000 psi, I think the ISP should exceed 330 seconds, or maybe 340 seconds. It’s been a while since I looked at my calculations on that. I suggest that route because Elon is probably not going to buy someone else’s overpriced engine, especially one from Rocketdyne/Arianne.

        Anyway, if Elon decides the Dragon 2 needs a lunar capable service module, he’ll probably come up with one quite quickly. Of course by that time it will be the Dragon 5B Full Monty v2.3 Mark 4 Block 6

        I had an idea for a lighter lander design that used a ring of descent/ascent thrusters for redundancy (such as an octoweb), surrounding a vertical airlock. The airlock would be where the engine bell is on the Apollo LEM, allowing convenient egress to the lunar surface. A small airlock with a ladder would work fine, while a big one could provide a place to strip off the outer space suit as a dust control measure.

        Place a Bigelow pop-up dome tent above the airlock, instead of a normal ascent module, both to reduce weight and decrease the payload volume for launch. By docking with the bottom end of the lander instead of the top end, an entire hatch is done away with, and the top doesn’t need to be anything more than a pop-up tent, although with one fold-out side for windows, flight controls, and displays.

        You could also put the ascent/descent engines on the very outside of the lander, as long as you had enough of them for engine out redundancy, letting them angle out during the final touch-down phase so it could set down on airbags instead of legs, which would probably save more weight.

        Using lots of smaller engines instead of one big one lets you achieve the same nozzle expansion ratios in a shorter length, which should lower the required height and perhaps the weight.

        1. I think you are right that Musk would prefer to stay in-house, and I also think you are right that he’d prefer a superdraco (due to already existing) plus an engine bell, and I think you’re right that’ll give 330+ (I’ve seen others speculate in that range or a bit higher, and I recall their math looked pretty good).

          So, what would be needed to give the Dragon2 a good (Apollo-SM comparable) SM, if we’re just talking Delta/v?
          IMHO, fuel, plus an engine, basically. I think you could fit sufficient tankage (And engine) in the trunk (I have not done the calcs to be sure, this is just a guess). It’s already a beefy-enough load structure. A huge problem IMHO with that notion is abort: Dragon2’s trunk is mass-limited for manned missions due to Dragon’s abort mode taking the trunk along for the ride.

          I like your lander ideas. One aspect I particularly like is it’d be mission flexible; some adaptions could be made fairly easily.

          I had some slightly similar ones a while back, though in my case the purpose was solely getting astronauts from LLO to a surface base and back. Ever seen the “flying bedstead” LEM trainer they used for Apollo? Roughly that configuration; basically chairs on top of a platform, spherical tanks and a couple of rocket engines under it. No pressurized area for the crew, use fast rendezvous and space suits instead. Saves a lot of mass.

          1. The trunk is basically there so they have a pickup truck mode for ISS deliveries, plus aerodynamic stability during an abort. I think it weighs less than 1000 kg.

            But I’ll bet they already have some rough design work on a real service module as part of their thinking on Red Dragon.

            As for the lander idea, I suppose in the minimalist case the Bigelow tent is one of those Space Shuttle rescue balls. ^_^

            Many years ago I went through a bunch of calculations on ascending from Mars in a chair and a space suit. It actually looks very promising, and max-Q was in the same range as riding a motorcycle down the highway.

          2. NASA made some preliminary studies of a similar system to return astronauts to lunar orbit if the LEM descent engine failed.

            Basically a couple of fuel tanks and a LEM RCS thruster or three on a metal frame. If the LEM failed they’d transfer fuel from the RCS to the rescue vehicle and fly it into orbit manually.

          3. In house, a better SpaceX alternative for a service module engine is the Kestrel pressure fed engine from the Falcon 1 rocket. I believe Musk recently tweeted his admiration of the Kestrel.

  2. One of the many problems I see with the Vice President’s speech is that his states in no uncertain terms that MSFC is the place from which this return to the moon is run. Then he says that there is no preferred contractor (i.e. Boeing), and no preferred way to get there, and everything has to be considered, yadyadyyady. It’s the MSFC part that is immutable, and, IMHO, the very thing that renders the whole thing impossible.

    I’ll repeat a comment I made on a previous post on this subject: NASA might be able to get a Risk Reduction Phase RFI on the street by 2024 – maybe….

    1. Totally agreed.

      Right now, if NASA needed one of the old apollo-style accel couches, which were tube and canvas, it would take them years and billions to get it done. SpaceX, on the other hand, would send somebody down to Home Depot to buy a lawnchair, which would do the job just fine.

  3. Well written. Thanks Dennis. So much so I will need to re-read carefully before I have anything intelligent to contribute.

    One question I have it whether it is really necessary to invent a new Lunar lander? Would it be possible to mod a propulsive Dragon capsule to get the job done? I was thinking that it might be possible to add skirt thrusters ala Gemini if necessary to create a “decent module” capability. You wouldn’t need the heat shield so that could go to help with the down-mass issue. The skirt ring and its landing legs would stay on the moon if the Dragons own SuperDracos could return it to lunar orbit.

    Since the “waste everything but time” approach would seem to
    emphasize using what’s at hand as much as possible. Of course in the Apollo era wasting money wasn’t necessarily a dis-qualifier. That may not be the case here either.

    Seems we have consensus about the multiple launch question. And frankly these days that seems to be no big deal like it might have been in the 60s.

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