For rockets going farther than ever, you need the best and biggest tools

Among NASA Michoud's unique gear: A 170-foot-tall, 78-foot-wide welding tool.

by Nathan Mattise and Jennifer Hahn

MICHOUD, La.—The scope of NASA's Space Launch System is unlike anything the organization has taken on before, and that's not only true of its deep space aspirations. Size is a factor, too

In terms of mere height, the SLS rocket will end up nearly 38-stories tall. Building and assembling something that unfathomably massive and unique (remember, it must traverse treacherous space environments) requires equally impressive tools. Luckily for NASA, that's exactly what its Michoud Assembly Facility can offer
.The manufacturing potential at MAF starts with the physical space itself. Michoud is both large (800+ acres with individual buildings that eclipse 40 acres by themselves) and navigable. It's located right up against waterways that allow for (relatively) easy transportation between partnering NASA facilities in the southeast. And inside the campus' individual structures, an intricate transportation system of cranes and rails allows the site's large, specialized tools to remain stationary. Individual components from any project are instead lifted and shifted from location to location, meaning Michoud's gear can be bigger and more complex without fear of constant recalibration. "[The tools here] are terrifically accurate, we're talking down to thousandths of an inch in accuracy," says Pat Whipps, the resident program manager at Michoud. "It's interesting. The tools are sometimes many stories tall, yet the manufacturing tolerance is down in thousandths of an inch."

That mass versus measurement dichotomy is probably best represented by Michoud's crown jewel—the Vertical Assembly Tool (VAT). Unveiled in the fall of 2014, this is the largest welding tool in the world at 170-feet-tall and 78-feet-wide. The mere spectacle of the facility that houses it attracted numerous Hollywood productions to film on location before everything was up and running (pay attention to the rappellers next time you watch GI Joe: Retaliation). Here, SLS fuel tanks (to hold liquid hydrogen and liquid oxygen), engine sections, and forward skirts will be assembled. Sometimes such parts are even cleaned within the VAT, making it "probably the biggest dishwater unit in the world" according to Whipps.

To put its work in simple terms, Jackie Nesselroad—a Boeing site leader and integrated product leader for the SLS project—says the tool is a “reverse PEZ dispenser.” Individual parts for the SLS rocket are loaded from the bottom and welded together, then the VAT raises everything up in order to repeat the cycle. Ultimately, SLS will piece together two domes and five 26-foot-tall barrel sections through this process.

When examined at a granular level, this work remains awe-inspiring. Michoud is an industry leader for a technique called friction-stir welding. Though it wasn't invented on site, MAF helped resurrect the practice and has since taken it to a scale never before seen. In friction-stir welding, a small, rotating weld-pin bonds the materials by using "more than 1,000 pounds of pressure," according to the local paper. The weld-pin generates enough heat through friction to send metals into a plastic-like state, allowing metal panels to be connected without jeopardizing their integrity. (Nesselroad can be seen discussing the technique in the video above around the 3:45-minute mark.) This ultimately creates a stronger and more accurate end-product. When we visited Michoud in late 2015, Nesselroad told us 70,000 inches—nearly 6,000-feet—of material had been welded to date without any defects.

The VAT (inside the VAC, Vertical Assembly Center) is merely the largest place on site where this type of work happens. But before tanks and domes can be put together, those individual components need to be assembled as well. This takes place at the (stay with us) Vertical Weld Center. This space was modified from Michoud's time working on the Ares program, and today it works on the SLS core stage. Individual metal panels enter, more friction-stir welding takes place, and out comes the barrels and domes that eventually head to VAT for larger-scale welding. Every individual barrel—recall, an SLS rocket requires five of them—is made of eight large panels.

With parts designed in nearby Huntsville, built in Michoud, and eventually tested at equally-closeby Stennis, folks like SLS Core Stage Lead Joan Funk have been able to observe the entire process firsthand ("I get the really fun part," she says). Yet despite how exciting the high-profile tests at Stennis have been, Funk admits there's something special about an old manufacturing hub continuing to learn new tricks. "This factory has been around in the WWII time frame, but we've managed to modify it and to use it," she says. "We have tools out here from the ET-days or longer, and it's nice that we can continue the process."

This video is part two of our four-part series on the Michoud Assembly Facility and how NASA's grand ambitions are playing out there today.

Listing image by Nathan Mattise

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