Tag Archives: Michoud Assembly Facility

A (much) Closer Look at How We Build SLS

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By Martin Burkey

How do you put the world’s largest rocket under a microscope?

One piece at a time, of course.

NASA’s Space Launch System – SLS – will be the world’s most powerful, capable rocket. It will send intrepid explorers, their spacecraft, their landers, their habitats, and all their other equipment to survive and thrive in deep space.

But, first, it has to survive launch. SLS is an extreme machine for operating in extreme environments – 6 million pounds going from zero to around 17,500 miles per hour in just 8 minutes or so after liftoff. Some parts are minus 400 degrees F. Some parts are 5,000 degrees. Extreme.

So NASA works hard to make sure everything works as planned, including the largest part, the core stage – 212 feet long, 27 feet in diameter, and weighing more than 2 million pounds all gassed up and ready to go.

NASA and core stage prime contractor Boeing are building hardware at Michoud Assembly Facility in New Orleans, Louisiana for the first flight in 2018. Engineers have put the design through numerous computerized structural analyses and simulations, but that’s not the same as actually cutting, welding, and assembling giant metal panels, domes, rings, etc. on new manufacturing tools with new processes for the first time. Each time, the team starts to weld new flight hardware, they methodically go through a series of steps to make sure that first flight hardware is perfect.

SLS liquid oxygen tank weld confidence article comes off the Vertical Assembly Center at Michoud Assembly Facility.

A liquid oxygen tank confidence article for NASA’s new rocket, the Space Launch System, completes final welding on the Vertical Assembly Center at Michoud Assembly Facility in New Orleans.

“Perfect” is a relative term. Some technically-minded people consider welding itself as a defect in a metal structure because the weld is never as strong as the rest of the metal, according to Carolyn Russell, chief of the metal joining and processes branch at Marshall Space Flight Center in Huntsville, Alabama, with 32 years of experience in the field. Given the advanced state of welding technology, other people might consider the term “defect” as a bit extreme.

None other than legendary rocket scientist Wernher von Braun declared in the midst of Saturn V moon rocket development in 1966: “A lifetime of rocketry has convinced me that welding is one of the most critical aspects of this whole job.”

The first step to SLS flight hardware was establishing the “weld schedule,” – how the welding will be done. SLS uses “friction stir welding” – a super fast rotating pin whipping solid metal pieces until they are the consistency of butter and meld together to bond the core stage’s rings, domes, and barrel segments. The result is a stronger and more defect-free weld, than traditional methods of joining materials with welding torches.

The completed SLS Launch Vehicle Stage Adapter awaits testing.

The completed SLS Launch Vehicle Stage Adapter (LVSA) structural test article awaits transfer to a test stand at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Measuring 56-feet tall, the LVSA connects the SLS core stage to the upper stage.

Based on the particular aluminum alloy and thickness, engineers establish the required pin rotational speed, travel speed, how hard it pushes on the metal Before committing the welding schedule to full size or flight hardware, the core stage team checks the process on test panels about 2 feet long. Test panels are made at Michoud and sent to Marshall, where they are nondestructively inspected, sectioned and then analyzed microscopically for minute defects.

A false color composite image of the metal grain in an LVSA panel.

A false color composite image produced by an electron beam microscope at NASA’s Marshall Space Flight Center shows the crystal orientation of a portion of the thickness of a metal panel for the Launch Vehicle Stage Adapter.

Marshall materials scientists study the samples under magnification in the search for cracks and voids, and to understand how deeply the weld penetrated the parts. They also undergo non-destructive evaluation, including x-ray, ultrasonic, and dye penetrant testing.

With weld processes tested for every part of the core stage, the manufacturing team can begin building weld confidence articles, or “WCAs.” There are WCAs for the engine section, the liquid oxygen tank, and the liquid hydrogen tank. Likewise, the WCAs are cut into samples that are again put under the microscope at Marshall. In theory, the WCAs should be perfect if the weld schedule was followed. In reality, it doesn’t quite work out.

WCA welding consists of lots of “firsts,” Russell explained. It’s a test of the tooling and factors like parts alignment and tolerances. Heat transfer from the welds to the surrounding metal is different once large parts are clamped together. It short, stuff happens. Adjustments are made. Weld samples are cut and again put under the microscope until the weld schedule is perfected.

All this testing and microscope-gazing has led to a major SLS milestone: the welding of structural test articles – STAs – and flight articles for the hydrogen and oxygen tanks, engine section, and forward skirt, which is underway now. The STAs will be shipped to Marshall next year. Secured into test stands – that are secured firmly to the ground – these test articles will be rigged with hundreds of sensors and then pushed and prodded to see if they can survive the stresses the flight hardware will experience – accelerating bending, twisting, etc.

Then, and only then, can engineers say that the giant core stage is ready for its launch debut. But that’s a story for another day.


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The Rocket Comes to the Rocket City

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By David Hitt

Over the next year, the rocket comes to the Rocket City in a big way.

Huntsville, Alabama, a.k.a. “Rocket City,” is home to NASA’s Marshall Space Flight Center, where today the Space Launch System (SLS), the powerful rocket NASA will use for human exploration of deep space, is being developed.

More than six decades ago – before NASA even existed – Huntsville laid claim to the nickname thanks to its work on missiles and rockets like the Juno that launched the first American satellite or the Redstone used for the first Mercury launches.

In the years since, Huntsville, and Marshall, have built on that legacy with work on the Saturn V rockets that sent astronauts to the moon, the space shuttle’s propulsion systems, and now with SLS.

New test stand at Marshall Space Flight Center

A steel beam is “flown” by crane into position on the 221-foot-tall (67.4 meters) twin towers of Test Stand 4693 during “topping out” ceremonies April 12 at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

While the program is managed at Marshall Space Flight Center, contractors around the country are building the rocket. Engines are being tested in Mississippi. The core stage is being built in Louisiana. Booster work and testing is taking place in Utah. Aerospace industry leaders and more than 800 small businesses in 43 states around the country are providing components.

The Marshall team has also been involved with the hardware, largely through testing of small-scale models or smaller components. The center also produced the first new piece of SLS hardware to fly into space – a stage adapter that connected the Orion crew vehicle to its Delta rocket for Exploration Flight Test-1 in 2014 (See Orion’s First Flight for more.) The same adapter will connect Orion to SLS for their first flight in 2018.

The top half of a test version of the SLS Launch Vehicle Stage Adapter on a weld tool at Marshall

Workers prepare the top half of a test version of the SLS Launch Vehicle Stage Adapter. The completed adapter will undergo structural testing at Marshall later this year.

Now, however, big things are happening in the Rocket City. The new Orion stage adapter for the upcoming launch is being built. The larger Launch Vehicle Stage Adapter, which will connect the core and second stages of the rocket, is being built at Marshall by contractor Teledyne Brown Engineering. This year, test versions of those adapters and the Interim Cryogenic Propulsion Stage (ICPS) will be assembled into a 56-foot-tall stack, which will be placed in a test stand to see how they handle the stresses of launch.

Those test articles built locally will be joined by larger ones produced at the Michoud Assembly Facility outside New Orleans. Test versions of the rocket’s engine section, oxygen tank and hydrogen tank will be shipped by barge from Michoud to Marshall. Two new test stands – one topped out last month at 221 feet tall – have been built at Marshall, joining historic test stands used to test the Saturn moon rockets.

The Payload Operations Center at Marshall Space Flight Center

In addition to rocket development, Marshall is involved in numerous other efforts, including supporting all U.S. scientific research conducted aboard the International Space Station.

Fifty-five years ago this month, Alan Shepard became the first American in space riding on a Redstone rocket, named for the Huntsville army base where his rocket had been designed – Redstone Arsenal. Today, Marshall, located on the same red clay that gave the arsenal and rocket their name, is undertaking perhaps its largest challenge yet – building a rocket to carry humans to the red stone of Mars.

Huntsville grew substantially from its small Southern town roots during its early days of rocket work in the 1950s and ‘60s, and Marshall has gone on to be involved in projects such as Skylab, Spacelab, the Hubble Space Telescope and the International Space Station, to name a few. But despite branching out its work both in space and other technology areas, Huntsville remains the Rocket City.

…After all, we built this city on a rocket role.


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