20 thoughts on “Monster Rocket Alternatives”

      1. The Falcon Heavy, taking cost and capability projections as accurate and assuming you need a large total payload, delivers a substantially improved payload/cost over the Falcon9 1.1. A 5 core Falcon extra-heavy dropping boosters in pairs may deliver even better payload/cost. Such a booster isn’t =needed=, but may be of benefit. The commonality with smaller launchers in the family should mean that you get a crew familiar with the systems even if the extra-heavy isn’t used often.

        A cost estimate needs to be made of the costs of splitting up your mission to multiple launches vs. the cost of developing the new rocket and support facilities. Assuming without analysis no net benefit from a better launcher is also an engineering mistake.

        1. A 5-core Super Heavy would not only require substancial modifications to the launch pad and other ground infrastructure, it would probably require substancial structural reinforcement to the central core. You’d then have to either support two different versions of the core rocket or make all cores strong enough to handle the heaviest loads. The first approach means changing your design and production processes to support the two versions. The other approach means that almost all of your cores would be considerably heavier than necessary for Falcon 9 and Falcon Heavy launches. If there were a market-driven need for launching such large payloads, I’m sure SpaceX would make the changes. However, unless that market materializes. there’s no need other than the desire for a really big rocket.

        2. How about a seven core with cross-feed and dropping in pairs (FH7)? Would we be getting to the point where even fuel transfer and waiting in LEO becomes unnecessary? By my calculations, it would put about 124 tonnes into LEO for each launch. Perhaps a bit more.

          1. Or you could go the other way and make it extremely tall so it takes a space elevator to get crew to the capsule? 😉

            Doesn’t SpaceX already have heavier lift concepts in the wings? FXX? FXXH?

          2. Because, as your numbers suggest (and assuming for the moment they’re accurate), you reach a point of diminishing returns. From the SpaceX website, a single core Falcon 9 V1.1 can put 13.1 metric tons into LEO. The three core Falcon Heavy is designed to put 53 metric tons into LEO. However, to go to your seven core monster, you’re only getting 123 metric tons to LEO (if that). However, in real cases, you’d have to give up some of that payload due to the added weight to handle the extra stresses. The current Falcon 9 core isn’t designed to handle those loads and would require substancial reinforcement. Giantism was a trait of the old Soviet Union to prove their engineering prowness but the result was seldom practical.

          3. I actually ran some rough numbers on a variant of that idea a few weeks ago in a comment at Selenian Boondocks, but used a Delta as the central core to get a fully cryogenic stage for better final performance.

            I’ll cut and paste it here.
            ***

            Assuming the boosters are stretched about 10% to give them a 200 second burn time (instead of 180), they’d have an empty mass of maybe 32,000 lbs and a wet mass of about 974,000 lbs [educated guesses]. Then take a Delta IV CBC (both stages) and add 150 metric tonnes of payload (330,000 lbs), to give a core/payload mass of 895,000 lbs.

            Arrange the boosters around the core in a square so that the engines at north & south are sustainers, cross fed from the corner engines just like a matched pair of Falcon 9 Heavies, and the engines at east and west are just stand-alone stap-ons. That gives you a lift-off mass of about 8.8 millon lbs and a lift-off thrust of 10.5 million lbs (from the 72 Merlin 1D’s on 8 boosters). The initial acceleration is 1.2 G’s.

            The corner engines burn out after 150 seconds, with the stand-alone boosters still having 25% fuel and the cross-fed sustainers having 75% fuel, and the total vehicle mass is 3.038 million pounds. The thrust prior to cutoff is about 11.5 million lbs (vacuum) and the acceleration would be 3.81 G’s, so you might want to throttle back a bit before that. The potential delta V to that point should be around 3 km/sec.

            After corner booster separation the vehicle mass drops to about 2.91 million pounds and the thrust is 5.78 million pounds (36 Merlins), so the acceleration drops to 2.0 G’s. At this point the vehicle is an X or a + configuration.

            At 200 seconds the stand-alone boosters burn out while the sustainers still have 50% fuel, with a vehicle mass of 1.97 million pounds. It would’ve been accelerating at 2.94 G’s prior to cutoff, and the potential delta V for that 50 second segment (leg 2) was 1.3 km/sec. After separation the mass is 1.9 million pounds and the thrust is 2.89 million pounds, giving 1.5 G’s.

            At 300 seconds the sustainers burn out. The vehicle mass was 960,000 lbs and the acceleration was back up to 3 G’s. After separation the mass is just the 0.895 million pound core stage (with the attached 150 tonne payload). The potential delta V for the 150 second leg 3 is about 2 km/sec, and the total delta V to that point is about 6.38 km/sec.

            Then the RS-68 on the Delta lights up with 785,000 lbs of thrust, producing 0.75 G’s. At about 543 seconds the main core stage burns out. The vehicle mass is down to 446,600 lbs and the acceleration was 1.7 G’s, and after separation the weight drops to 385,000 lbs. The delta V from the RS-68 was 2.8 km/sec, and the total to that point is 9.2 km/sec.

            Finally the little tiny RL-10 on the Delta IV upper stage adds 0.56 km/sec to bring the total delta V to 9.7 km/sec, which is at the high range of what it usually takes to get a rocket into LEO. If I run the numbers with a 200 tonne payload my simple spreadsheet shows 8.9 km/sec delta V.

            It would be interesting to run some real numbers through some actual software, with an additional allowance for the increased structural weight on the Delta IV to support such a large payload at 3+ G’s, and ditching the expensive RL-10 second stage entirely.

  2. Your best line in your old post: they’ve skipped past the part of the trade studies that would determine whether or not this assumption is valid, and gone straight to debating the best way to get heavy lift.

    We don’t even need the Falcon Heavy, although it does have the advantage that Elon has already put a price on putting a four person, 25mt lander in mars orbit of $150m to $195m.

    We don’t even need depots in a sense since the transfer ship itself is a depot. We just need to be able to transfer fuel. It sits in orbit while accruing enough fuel for the delta V required. Leasing space on it provides revenue while you wait. The pioneer colonists will have a cramped ride, but it should not be in the Orion. The discontinued (but easily restarted) Sundancer is less massive (F9 will do) and has more internal space (22 m3 ea. if 8 crew.) It should not be too hard to upgrade it to life support for six to eight so only two landers are required to take them to the martian surface.

    I would include ion engines for orbital insertion and return to earth. Most of the Merlin (or whatever engine) fuel is used up in the initial burn so you don’t have to worry about some shrapnel depriving you of fuel for orbital insertion. Later I expect we can do much better than the Sundancer or BA330 (perhaps from competition to Bigelow?)

    Total mission cost? $700m for 4 vehicles (8 colonists) and aprox. $500m for transit fuel. Nobody will beat that. However, they should also include precursor supply mission ($195m ea.) Some to the landing site and some in mars orbit for right after the first humans land.

    The only thing we need is testing of the lander which Mars One may do for us. It’s mostly off-the-shelf otherwise.

    Note: this is not saying no depots. It’s just saying include a gardener’s shack.

      1. 2.5mt of payload, lander. Sorry Rand… I really do try not being stream of conscious and really do understand how annoying it is. Please forgive.

  4. Remember the other Von Braun plan? The one with the in-orbit EOR assembly using a dual-launch architecture with the Saturn C-3. Well the Saturn C-3 was supposed to have the same payload as the one proposed for the Falcon Heavy. Perhaps I just spent too much time playing Buzz Aldrin’s Race Into Space. Which BTW you can now get for free here:
    http://sourceforge.net/projects/raceintospace/

    I am not related to the project I just think that old game is cool.

    1. Well, Dynetics in Huntsville is resurrecting the F-1A engines for SLS strap-on boosters. The F-1’s are nice, but their specific impulse is pretty low, so an RD-170 outperforms them by leaps and bounds.

      1. The work that Dynetics is doing on the F-1 is to not only increase performance but to simplify the design and use modern production techniques for lower cost manufacturing.

        The prototype components were constructed not with welding and casting, but rather with selective laser melting—a 3D printing technique that uses hot lasers to fuse metal powder into complex shapes. Dynetics and Pratt Whitney Rocketdyne hope to lean heavily on advanced manufacturing techniques like this in order to massively reduce the part count—and hence cost—of the F-1B engine compared to its F-1 predecessor. Current estimates call for a reduction in the combustion chamber from more than 5,000 parts in the F-1 to fewer than 100 parts in the F-1B.

        Yes, higher Isp is nice but not if you can’t afford it. The Dynetics SLS strap-on design uses two F-1B engines on each side.

      2. Well, if they get the cost down to around ten times that of a Merlin, they’ll have an engine that would be in the ideal range for a single-engine first stage for medium lift, performing like a hypothetical 12 or 13 engine Falcon.

  5. SpaceX is already experimenting with 3D printing of engine parts. Which are more likely to be used for an actual engine that will fly on an actual rocket.

    Besides once you rebuild the F-1A engine entirely can you even still call it an F-1A engine? It is an F-1A class engine but it has little to do with it. Nothing against the concept but I think the idea comes a bit late in the program and SLS is a boondoggle. At minimum they should put a stop on it and rethink it from basic principles. Even if something good may come out of it I doubt it will get used in an meaningful way. Remember the X-33 composite LOX tank or the metallic heat protection tiles? Yeah me neither.

    1. Besides once you rebuild the F-1A engine entirely can you even still call it an F-1A engine?

      Probably not. That’s why they’re calling it the F-1B.

  6. > Doesn’t SpaceX already have heavier lift concepts in the wings? FXX? FXXH?

    Elon said that those concepts were just talk and not serious plans. The F9 cores serve a commercial demand. It doesn’t seem to me that the market is demanding an FX_. Only the govt has need for sizeable payload beyond GEO. But if there is a way to provide that demand using commercially-viable launchers then those launchers would have the flight frequency needed to keep the launcher cost down.

    1. I remember proposals for circumlunar flights aboard a ferry spaceship of some kind for sightseeing tourists. So the potential market is certainly not zero.

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