Wednesday, February 19, 2020

SpaceX Eying Water Tower Assembly for Better Ways to Build Stainless Starship

SpaceX is nothing if not a disruptive force in the aerospace industry.  From the hi-tech company model of prototype as soon as possible, fail early and correct quickly to the industry leading recovery and reuse of boosters, they seem to be always innovating and always pushing forward.  To borrow the cliche', they're always thinking outside the box.

I admit to missing this story on the 6th when Teslarati published it, but in the effort to improve the manufacturing of their stainless steel Starship, they're looking into the machines that build water towers to find ways to make the assembly faster and higher quality.  The first revision of this article included the following text:
A SpaceX engineer says that the company wants to adopt commercially-available manufacturing equipment that could allow its Boca Chica, Texas team to build Starship tank parts in minutes and nearly-complete rocket bodies in a matter of days.

Originally created to meet the needs of a variety of different companies – typically oil and gas related – that need efficient, affordable, and standardized storage tanks, a small but growing niche exists for semi-automated tank production. While there is some clear uncertainty given that the quality and consistency required for oil and gas needs or even simple water storage likely isn’t the same needed to meet strict spaceflight margins, SpaceX has already acquired several production tools from existing contractors and is working around the clock to prove that those same tools can be used to build large, reusable rockets.

The gamble is simple: if it turns out that off-the-shelf (COTS) equipment can become an almost turnkey solution for manufacturing high-quality Starship spacecraft and Super Heavy boosters, SpaceX may have found a shortcut to orbit, avoiding the huge expense of finding and building its own custom production solutions. But is that COTS tank fabrication hardware truly up to the task?
In response to that final question, Elon Musk replied to the Teslarati team with a lot of detail.  It now leads the article off.
This isn’t quite correct. An orbital rocket needs precision that’s 3X to 4X better than a water tower, so super precise parts, fixtures & welding are needed. Suborbital is much more forgiving.

That said, although substantial capital & engineering is required to achieve extreme precision, marginal production cost of the primary structure should actually be *less* than a water tower, because it’s built inside a factory in volume.

Unmodified water tower machines do not work well for orbital rockets, as mass efficiency is critical for the latter, but not the former. Hopper, for example, was made of 12.5mm steel vs 4mm for SN1 orbital design. Optimized skins will be [less than] 2mm [thick] in places across a 9000mm diameter. [Note: everything in square brackets my edits -SiG]
An interesting problem is how to support these 9 meter diameter steel skins that are 2 mm thick.  That's close to .080" thick across 29-1/2 feet diameter.  It ought to behave like an overgrown piece of paper with those dimensions.

The fact that SpaceX engineers are studying how the oil and gas industry gets tanks fabricated and how to modify those welding machines for the higher precision they need for spaceflight is interesting enough in itself.  If a solution to a similar problem already exists, it's generally cheaper and easier to adapt the old tool to the new problem than to invent an entirely new tool.

SpaceX's second test tank made it to about 50% higher pressure than it was required to survive, demonstrating that it's safe enough for manned space flight.  This was all hand-welded by very skilled welders on fixtures SpaceX developed.


  1. Soooo.... The technology to create inexpensive (in consideration to what exists now) rocket components has always been around.

    Very interesting.

    And yet ULA has been using the same tooling and the same materials now as they started out with 30-40-50 years ago. Because that's the way it's always done (and it's cheaper and better for them to do it the hard way.)

    This is the way true innovation works. By searching for the better, simpler way to do things.

    Go, SpaceX, GO!

  2. I suppose they could roll some "ribs" into the sheets as they form them. High-precision automated welding has been around quite a few years, too.

    Reduced to the basics, they're making metallic cylinders with domed ends. Nobody's ever tried to cost-contain rocket tank construction because it didn't matter. The only thing that mattered was making it strong enough, and light enough, to get the job done, and costs be damned. We have Russians to beat, don't ya know?

  3. You guys should really follow the discussion fora on NasaSpaceFlight(dot)com. This was discussed over a year ago. There was a lot of debate about whether these machines were applicable to building Starhopper, and in the end they just did it manually – but they did use water tower fabricators to help build it.

    There are good discussions by professionals about Starship manufacturing progress, Starship/SuperHeavy engineering, problems with orbital refueling, Mars colony development, the use of SS/SH on Luna, rocket engine development and chemistry, Blue Origin's progress or lack thereof, and just about any other space-related topic you can think of.

    1. I go to NASASpaceFlight from time to time and find that they're a good source but occasionally miss stories - as everyone seems to. I'm sure I've posted links to them before.

      I haven't joined the forums because there's only so many hours in a day, even for retired folks.

    2. I hear ya on time! I haven't joined the forums either, but they're fun to read. I was riveted to the daily photos and videos coming out of Boca Chica while they were building Starhopper (for many months peope were seriously convinced it was a water tower), and due to the omnipresent video volunteers that published there I caught the flight of the hopper real-time as it happened.

      I concentrate on space blogs to stay sane in a world that is going mad.

    3. I've been a member over there since around 2004 when I started working for Sea Launch. Good forum, but I'm not in that business any longer, and as SiG says, even retired people need to manage their time.....

    4. "Retired people" is a phrase in dire need of retiring. I left Boeing in 2013, and I haven't worked harder at any time in my life than I have since then. (No "Lazy B" jokes, please! I was in R&D and worked my backside off.)

    5. I've got a friend who retired from the Army 20 years ago and says he hasn't worn a watch since then. I wear one every day. I need to set an alarm on my phone a few days every week.

      I tell people that the key to a fulfilling, happy retirement is to be a self-starter. Most don't get it.

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