When you're building the largest rocket in history, normal tools just won't do. To construct its Space Launch System, NASA has had to develop a host of new welding equipment, and last week the agency unveiled the largest spacecraft welding tool in the world, the Vertical Assembly Center at the Michoud Assembly Facility in New Orleans. This single welding tool is 170 feet tall and 78 feet wide, and is custom designed to build the massive core stage of NASA's next-generation space launch vehicle.
The SLS, which is slated to launch for the first time in 2017, is a multistage rocket. The core stage, which stands 200 feet tall and measures 27.6 feet around, is the system's main power house. This stage will hold the liquid oxygen and hydrogen thanks and all the plumbing needed to drive fuel into the four space shuttle heritage RS-25 engines.
Flanking this core stage will be two solid rocket boosters of the sort used by NASA's retired shuttles. Topping the core stage will be an adapter followed by an optional upper-stage and finally the payload. This baggage will be either a manned spacecraft or simply cargo, depending on the mission at hand. This will be the first rocket to dwarf the Saturn V, albeit barely. The SLS will generate between 8.4 and 9.2 million pounds of thrust, depending on its configuration.
It's the core stage that the new VAC will help build. "One of the challenges that we face in building this large core stage is to develop world-class tooling using modern manufacturing methods in an affordable way, while maintaining the scheduled first launch in 2017," said Tony Lavoie, manager of the Stages Office at NASA's Marshall Space Flight Center, in a statement. "This tool set that we've developed for Michoud to build the core stage is a perfect blend of those requirements and constraints."
Six different welding tools will go into building the SLS' core stage. There's the Circumferential Dome Weld Tool that will perform friction stir welds for the domes that cap off the stage's cryogenic fuel tanks. And there's the Gore Weld Tool that will perform vertical conventional friction stir welds to make gores—pre-formed aluminum alloy segments that are welded together to make the dome—for the tanks.
There's also the Vertical Weld Center, a massive unit three stories tall that weighs 150 tons, that will friction-stir-weld barrel panels together to produce the fuel tanks and other large portions of the spaecraft. Together, these domes and barrels make-up the core stage structures: the forward skirt (housing the electronics responsible for controlling the booster rockets), the liquid oxygen tank, the intertank (which transfers loads between fuel tanks), the liquid hydrogen tank, and the engine sections.
The last and largest of the welding tools, the 170-foot tall behemoth at Michoud, is the Vertical Assembly Center. This is the tool that will weld everything the other tools build together, turning the domes, rings, and barrels into a proper complete rocket stage. The VAC will also perform nondestructive evaluations of the completed welds to make sure the stage is fit to fly.
"That old saying, 'measure twice, cut once,' applies in spades when you're building a 5.5 million-pound rocket," said Rick Navarro, Boeing operations manager at Michoud. "We do a lot of testing, validating, and what we call 'qualifying' welds that ensure we have all the information we need to build with 100 percent quality assurance."
Both the rocket's core stage and its two external boosters have so-far passed critical design reviews, putting the program into the development stage, a major milestone. And construction on certain pieces of the SLS has already begun, including the welding of 10 barrels using the Vertical Weld Center.
Now, with the VAC ready to work, things are looking good for the SLS. "We are one step closer to building the first core stage in what will hopefully be a long line of rockets to support future NASA missions," said Lavoie. NASA Administrator Charlie Bolden echoed this sentiment at the ribbon-cutting ceremony at Michoud on Friday: "This rocket is a game changer in terms of deep space exploration and will launch NASA astronauts to investigate asteroids and explore the surface of Mars while opening new possibilities for science missions."
There are plenty of reasons we should all want to see the SLS launch on time. NASA hasn't had a heavy-lift launch vehicle since the Saturn V, and regaining that capability promises to give America a way to launch its own astronauts into space again, while also shortening transit times to distant destinations like Mars and Jupiter. It bodes well, then, that the tools to build the rocket are finished. And given the ongoing volatility of American politics (and, thus, funding), moving the project along as quickly as possible is in the best interests of our space exploration future.