20 thoughts on “The Hopper In Boca Chica”

  1. The linked article has some pictures copied from Twitter. A couple of them show sections with, I guess, the stainless skins mentioned recently. They look kind of…crinkly, I guess, like aluminum foil, especially the one with two cylindrical sections side by side.

    “Is that normal” isn’t really the right question here. Is it OK? Or is it possible/likely that they’re going to do something to smooth the skin out somehow before a launch?

    1. If, as seems likely, the skins are also the tankage, then pressurizing them for flight should smooth them out nicely. I don’t think the overall design is like the stainless balloon tankage of the old Atlas rockets, but the effect of pressurization should be similar.

  2. The bottom section (the one with the legs) was built of mill finished stainless steel plate, which they have subsequently sanded making it a bit more reflective. The middle and upper sections (which have just been stacked — see this NSF post with the latest photos) have been loosely described as being foil over a rebar frame, but are actually built from sheets of polished stainless steel sheet metal over a bent and welded square tubular frame, all spot welded together.

    The lower section looks quite sturdy, and there is debate as to whether it will use integral tanks or have separate tanks installed in it. The upper sections certainly to look flimsy, but they are probably a bit sturdier than they look, and I’d expect them to withstand the stresses of short hopper tests. This is certainly not a reentry test vehicle. (A minority of commenters believe that the middle and upper sections will be part of a balloon tank which will smooth out upon pressurization.)

        1. I hadn’t been following this closely. I just assumed it was sometime in the indeterminate future. But those photos show they are wasting no time in assembling that thing and getting ready for flight tests.

  3. Something to refine how the engines and steering jets handle the last 10-to-20 meters above ground? It would be embarrassing, and expensive!, to lose control and crash after an otherwise successful flight.

    1. I think you are right on target with the “expensive” concern. What they are building now is a fairly cheap, low fidelity prototype, and they will try to retire as much risk as possible before completing and shifting testing to an expensive, high fidelity prototype. If they crash this one, then they will have learned something in the process, and could quickly crank out a new one to continue testing.

  4. I think the OML of Starhopper may match the OML of the Starship Tanker. We know, from Musks various statements, there are going to be at least three versions of Starship, which we might call Tanker, Freighter, and Liner. He’s also said the OML of Tanker will be different from the others, because fuel is denser than people, things, and air. So this is unlikely to be just some random shape. I also think there’ll one day be two versions of the Freighter, one matching the “chomper” shown deploying a large space telescope, the other being like the Liner, but with loose cargo intended for delivery to planetary surfaces. We’ll see.

    1. For dirt-side cargo runs, they might as well use a stripped-down Liner variant, since it’ll already have to have things like a slide-out elevator/crane. If I were designing them, I would use the Freighter strictly for delivery to space, and the Liner for everything else. I would also either build the Freighter first, or have a plan in place to deploy satellites through the side hatch on the Liner, since that’s where most of my future income would be coming from (assuming that’s even possible, given that satellites are typically longer than they are wide due to current fairing shapes).

      The only reason to build a true fourth variant would be if the internal walls and human-centric infrastructure are a) integral to the Liner and cannot be removed, and b) too heavy to simply ignore the problem and launch with them.

      In other news, Elon appears to be going with a completely new bell design that tries to have its vacuum Isp cake and eat it, too. At this rate, I almost wouldn’t be surprised if he were to announce a sudden switch to an aerospike (likely doubling as a heat sink for atmo entry) at the last minute.

      1. I think the “one spaceship to rule them all” paradigm was a bigger part of what lead to SLS not working out as we all hoped than is generally acknowledged. Doing the same thing with Starship might be an even bigger mistake (and we do know better now)

        It helps to think of Starship as if an upper stage + payload combo, different from traditional only in that we get the whole package back. The propulsion section (engines, tankage, and vanes/legs) is the same for all variants. What’s above that is payload, and we shouldn’t think of it as a universal satellite bus. Instead, the Spaceship payload is Liner (Manned spacecraft with ECLSS), Freighter mk 1 (Liner with cargo space and handling equipment instead of crew accommodations) and, indeed, the first few crews Spaceships might be hybrids, arriving at Mars, for example, with 20 or 30 crew and 60 or 80 tons of cargo. But those two are the only two interconvertible (and then only if it’s cost effective, which I doubt). The third spaceship is the Tanker, which has a different OML and accounts for a majority of Spaceships. Finally, we’d have the reighter mk 2, with the same OML as the other non-Tankers, but with a big, open cargo bay and a large cargo bay door. That’s the “chomber” satellite delivery vehicle, mainly flying to LEO and GEO.

        The reason I think we’ll end up with permanently configured Starships has to do with numbers. Peoe around the Interdweebz are talking about very low numbers, for example, one booster with a few Starships assigned to it, no more than six to twelve total. That’s STS thinking. There were ever only 6 complete Orbiters built, one of which never flew in space (Enterprise). I think there will be hundreds of Starships built over the next 20 years (until the design is superceded by something better). If Musk is going to build a city on Mars, that’s what’s needed. If it’s just a reusable SLV, then who cares?

        1. More than 6 Starships will be required if they need to stay on the Martian surface. If they’re just ferries back and forth, fewer may be required initially, but Elon doesn’t strike me as the kind of person who would build “just barely enough to get by” of pretty much anything (announcing that “everything is ready” when it is in fact barely ready to go, on the other hand…).

          By the same token, why put all of one’s engineering efforts into launch-able/land-able Starships? Why not build a few to get started and then move towards on-orbit assembly? Build heavy, shielded inter-planetary ferries with vacuum-optimized propulsion systems that never need to land, and ferry people between orbital inter-modal stations.

          Yes, the latter path is still fictional to a certain extent, but it makes sense to me to get where you need to be for the time-being, and keep resources available for future improvements and ideas. Musk has already shown he’s willing to do this vis a vis retiring Falcon 1 for Falcon 9, halting Falcon 9 iterations after Block 5, eventually scrapping Falcon Heavy, etc. So it may not be that Musk sees 6 Starships as “all that we’ll ever need” as much as “the prudent first step before we find what is surely an even better way to do it”.

        2. Think of SpaceX’s business model, though. Their primary means of income revolves around satellites, and that’s not going to change (especially if StarLink works out). Because Starship is supposed to be cheaper to fly than an expendable second stage(!), Elon plans to drop all previous designs once it enters regular service. Soooo, while he needs a Liner to get paid for his Apollo 8 re-run, a satellite delivery system needs to be the top priority. If this can be done by kicking satellites sideways out of the Liner’s cargo hatch, fine; otherwise, Pac-MaX needs to be developed in parallel or even prior to the Liner (which is probably a good idea anyway, given all the life support and interior layout work that needs to be done for the Liner).

          Given how SpaceX likes to iterate, I wouldn’t even be surprised if the first Starship or two are a simplified cargo variant with no refueling capability–there’s plenty of demand to keep them busy while more are built (and yes, there will have to be dozens/hundreds eventually, especially for Mars colonization).

  5. The latest photos out of Boca Chica show that they are cladding the lower, plate stainless steel (mill finished, then sanded, but not polished), cylindrical section of the hopper with polished stainless steel sheet metal sheets.

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